TRANSPORTATION RESEARCH DIGEST

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TRANSPORTATION

RESEARCH DIGEST



MAY

2007




















ARIZONA TRANSPORTATION INSTITUTE


e
-
mail
jsemmens@cox.net




2














The contents of the
Transportation Research Digest

reflect the views of the aut
hors who
are responsible for the facts and the accuracy of the data presented. The contents do not
necessarily reflect the official views or policies of the Institute

.
TRANSPORTATION RESEARCH DIGEST

ARIZONA TRANSPORTATION INSTITUTE

e
-
mail
jsemmens@cox.net



MAY 2007



TO:

TRANSPORTATION PROFESSIONALS, MANAGERS, & POLICY MAKERS


FROM:

ARIZONA TRANSPORTATI
ON INSTITUTE




The volume of information on transportation issues, policies, technologies, and related
topics is huge. Not even the most well
-
read professional can keep up with everything that might be
useful to know. The
Transportation Research Digest

se
ries is designed to expedite the transmission
of information by condensing and summarizing significant documents. Busy professionals or
managers may quickly obtain the gist of new developments and determine whether they need to see
the full document.



The

Transportation Research Digest

is not meant to present definitive resolutions of
scientific or policy controversies, but contributions to the pursuit of knowledge and the debate of
issues. The intent is to be comprehensive rather than conclusive on the mu
ltitude of issues and
topics of concern to those working in the field of transportation. Readers are encouraged to obtain
the original document summarized in the
Transportation Research Digest

and subject the content to
their own judgment.



Transportation

professionals who would like to recommend documents to be summarized or
submit summaries to be considered for inclusion in this publication are invited to do so. To
recommend a document please send a copy (or information indicating how a copy can be obtai
ned)
of the research report to be summarized. To be considered, the report must meet the following
requirements: (1) it is transportation related, (2) it is no more than two years old, (3) there is enough
information in the report to warrant a two page sum
mary. To write a summary, insure that the
document being summarized meets the above requirements. The summary should be submitted in
an electronic format. This summary should be in the 500 to 800 word range and may include tables
and/or simple graphics

all

of which must fit within the

Transportation Research Digest

s
two
-
page format. Submissions are subject to editing for clarity and length. We do not guarantee that all
submissions will be published.



If you would like to obtain the full report upon which
a
Transportation Research Digest

summary is based you have several options. Check your local university library. You may want to
contact the publisher using the contact information appearing in the
Transportation Research
Digest
. Some of the documents are
free for the asking. Others can be purchased.



There is a database listing of all the previously published
Transportation Research Digests

that we have on file
(back to 1984).

Copies of the list or of portions of the list selected by topic or
mode can be
provided on request. You may also access the database via the internet at



4

Transportation Research Digests

from December 1995 to November 2003 are available at

http://www.
dot.state.az.us/ABOUT/atrc/Publications/DocRev/TRDtest.htm




A

Topic


code in the Table of Contents will help readers more quickly identify items of
interest. The topic codes are explained in the table below.


Code

Topic


Code

Topic

ADM

Administration


PLAN

Planning

AIRP

Airports


PRIV

Privatization

AVIA

Aviation


RAIL

Railroads

BI
KE

Bicycles


RDSD

Roadside

CON

Construction


ROW

Right
-
of
-
Way

ECON

Economics


SAFE

Safety

ENV

Environment


STR

Structures

FIN

Finance


TECH

Technology

INOV

Innovation
s


TOLL

Toll Roads

MAIN

Maintenance


TRAN

Transit

MISC

Miscellaneous


TRF

Traffic

MVD

Motor Vehicle Dept


TRK

Trucking

PAVE

Pavement


VEH

Vehicles



Requests or inquiries may be made via e
-
mail (jsemmens@cox.net).



Thank you.

TRANSPORTATION RESEARCH DIGEST

ARIZONA TRANSPORTATION INSTITUTE

e
-
mail
jsemmens@cox.net



MAY 2007



TABLE OF CONTENTS


Topi
c

Title

Pages

CON/

best
value

Best
-
Value Procurement Methods for Highway Construction Projects
,
NCHRP Report 561

by Sidney Scott, III, Keith R. Molenaar, Douglas D.
Gransberg, Nancy C. Smith (Transportation Research Board, 500 Fifth Street,
NW, Washington
, DC 20001; (202) 334
-
3213; http://gulliver.trb.org/bookstore)
(2006)

Use of best
-
value procurement in a variety of different forms resulted in
cost or time improvements or both.

9
-
10

CON/

riprap

Riprap Design Criteria, Recommended Specifications, and Qua
lity Control
,
NCHRP Report 568

by P. F. Lagasse, P. E. Clopper, L.W. Zevenbergen, J. F.
Ruff, Ayres Associates Inc. Fort Collins, CO (Transportation Research Board,
500 Fifth Street, NW, Washington, DC 20001; (202) 334
-
3213;
http://gulliver.trb.org/booksto
re) (2006)
Guidance on determining design
variables and design examples are provided for each application.

11
-
12

PAVE/

moisture
damage

Guidelines on the Use of Underseals as a Pavement Moisture Barrier

by
Cindy K. Estakhri and Shiva Ramakrishnan, Texas Tr
ansportation Institute,
Texas A&M University System, College Station, Texas 77843
-
3135 (Texas
Department of Transportation, Research and Technology Implementation
Office P.O. Box 5080, Austin, Texas 78763
-
5080;
979.845.1734;
http://tti.tamu.edu
) (Aug 2006)

Underseals can be very effective in protecting
base materials from the intrusion of surface water.

13
-
14

PAVE/

asphalt

I
-
70 Glenwood Canyon Overlay
w
ith Trinidad

Lake Asphalt/Steel Slag Hot
Mix Asphalt

by
Robert Laforce
, Yeh and Associates, 5700 E. Evans

Ave.,
Denver, CO 80222 (Colorado Department of Transportation


Research, 420 I
E. Arkansas Ave., Denver, CO 80222) (Sep 2006)
This study was unable to
identify superior performance of the TLA/steel slag mix.

15
-
16

PAVE/

ultra
-
high
perform
concrete

Mater
ial Property Characterization of Ultra
-
High Performance Concrete

by
Benjamin A. Graybeal, PSI, Inc., 2930 Eskridge Road, Fairfax, VA 22031
(Office of Infrastructure Research and Development, Federal Highway
Administration, 6300 Georgetown Pike, McLean, Vir
ginia 22101
-
2296) (Aug
2006)

Ultra
-
High Performance Concrete (UHPC) displays significantly
enhanced material properties compared with other concrete.

17
-
18


6

PLAN/

software

Benefits Estimates of Highway Capital Improvements with Uncertain
Parameters

by Jame
s H. Lambert and Nilesh N. Joshi, Virginia Transportation
Research Council, 530 Edgemont Road, Charlottesville, VA 22903 (Virginia
Department of Transportation, 1401 E. Broad Street, Richmond, VA 23219)
(Sep 2006)
The project developed software to provide
the DOT with additional
methodology for benefits estimation, which the agency can use to distinguish
among candidate projects.

19
-
20

PLAN/

multi
-
modal

Comparison of Virginia's Multimodal Transportation Corridors Using Cost
and Demographic Analyses

by Jame
s H. Lambert, Alexander S. Linthicum,
and Shadi M. Wadie, Virginia Transportation Research Council, 530 Edgemont
Road, Charlottesville, VA 22903 (Virginia Department of Transportation, 1401
E. Broad Street, Richmond, VA 23219) (Sep 2006)
Transportation pla
nning
agencies should work toward the goal of accurately quantifying benefits, thus
enabling the use of proper cost
-
effectiveness and cost
-
benefit methods of
analyses.

21
-
22

SAFE/

intersect

Rural Expressway Intersection Surveillance for Intersection Decis
ion
Support System

by Lee Alexander, Pi
-
Ming Cheng, Max Donath, Alec
Gorjestani, Arvind Menon, Bryan Newstrom, Craig Shankwitz, Nic Ward, and
Ray Starr

in Transportation Research Record 1944

(Transportation Research
Board, 500 Fifth Street, NW, Washington,

DC 20001; (202) 334
-
3213;
http://gulliver.trb.org/bookstore) (2006)
An intersection decision support (IDS)
system design has been developed.

23
-
24

SAFE/

POE

Trade
-
Offs Between Security and Inspection Capacity: Policy Options for
L
and Border Ports of Entr
y

by Hilma Villegas, Patrick L. Gurian, Josiah M.
Heyman, Adrian Mata, Robert Falcone, Edward Ostapowicz, Steven Wilrigs,
Michael Petragnani, and Eric Eisele

in Transportation Research Record 1942

(Transportation Research Board, 500 Fifth Street, NW, Washi
ngton, DC 20001;
(202) 334
-
3213; http://gulliver.trb.org/bookstore) (2006)
Diverting more traffic
into the Secure Electronic Network for Travelers Rapid Inspection (SENTRI)
program appears a reasonable compromise solution.

25
-
26

STR/

ultra
-
high
perform
co
ncrete

Structural Behavior of Ultra
-
High Performance Concrete Prestressed I
-
Girders

by Benjamin A. Graybeal, PSI, Inc., 2930 Eskridge Road, Fairfax, VA
22031 (Office of Infrastructure Research and Development, Federal Highway
Administration, 6300 Georgetow
n Pike, McLean, Virginia 22101
-
2296) (Aug
2006)
Ultra
-
High Performance Concrete is a viable substitute for other concrete
in prestressed I
-
girders.

27
-
28



7

TOLL/

HOT
lane

HOT Lane Buffer and Mid
-
Point Access Design Review Report

by Carter
Burgess in associa
tion with Wilbur Smith Associates; The Resource Group;
Perteet; EnviroIssues; IBI Group; Demich Consulting (Washington State
Department of Transportation, Planning and Programming Service Center,
Research Office, Olympia, Washington 98504
-
7370) (Oct 2006)
The purpose
of this report is to provide an overview of buffer and midpoint access designs
for concurrent flow, high occupancy toll (HOT) lanes that are either in
operation or under study and to recommend the preferred buffer and access
designs for these f
acilities.

29
-
30

TOLL/

congest
pricing

The Price Is Wrong: Why Our Roads Are So Clogged

by Joseph Giglio (
TCS
Daily
, http://www.tcsdaily.com/;
http://www.tcsdaily.com/article.aspx?id=021307C) (Feb 13, 2007) Congestion
pricing allows consumers to decide wh
ether the price charged for a given trip is
worth their travel time savings. We can charge motorists for using roadways
without forcing them to stop at toll
-
booths.

31
-
32

TRAN/

TECH

Using Archived AVL
-
APC Data to Improve Transit Performance and
Management
, TCRP Report 113

by Peter G. Furth, Brendon Hemily, Theo H.
J. Muller, and James G. Strathman (Transportation Research Board, 500 Fifth
Street, NW, Washington, DC 20001; (202) 334
-
3213;
http://gulliver.trb.org/bookstore) (2006)
Automatic data collection c
an
revolutionize schedule planning and operations quality monitoring as agencies
shift from methods constrained by data scarcity to methods that take advantage
of data abundance.

33
-
34

TRF/

TECH

Benefits of Signal Timing Optimization and ITS to Corridor O
perations

by
Lloyd J. French. and Millie S. French, French Engineering, LLC, 114 Cooley
Estate Rd., Smithfield. PA 15478 (Pennsylvania Department of Transportation,
Bureau of Planning and Research, Commonwealth Keystone Building, 400
North Street. 6
th

Floo
r East, Harrisbur g. PA 17120) (Aug 2006)
The purpose of
this research was to develop and use the SimTraffic microsimulat ion model in
the assessment of signal timing alternat ives on a congested corridor.

35
-
36

TRF/

congest

Component s of Congest i on

by Jaimy
oung Kwon, Michael Mauch, and Pravin
Varaiya

in Transport at ion Research Record 1959

(Transportation Research
Board, 500 Fifth Street, NW, Washington, DC 20001; (202) 334
-
3213;
http://gul li ver.t rb.org/bookstore) (2006)
33% of all delay could be eliminated
b
y ideal ramp metering.

37
-
38


8

TRF/

congest
pricing

Congestion Pricing: A Primer,
by Patrick Decorla
-
Souza (Federal Highway
Administration, Office of Transportation Management, HOTM, 400 Seventh St.
SW, Room 3404, Washington, DC 20590;
http://www.ops.fhwa.d
ot.gov/publications/congestionpricing/congestionpricing.
pdf; phone: (202) 366
-
4076; E
-
mail:
Patrick.Decorla
-
Souza@dot.gov
) (Dec
2006)
Congestion pricing benefits drivers and businesses by reducing delay
s,
increasing the predictability of trip times, and allowing for more deliveries per
hour.

39
-
40

TRF/

congest

Do Employee Commuter Benefits Reduce Vehicle Emissions and Fuel
Consumption?

by Erik Herzog, Stacey Bricka, Lucie Audette, and Jeffra
Rockwell

in

Transportation Research Record 1956

(Transportation Research
Board, 500 Fifth Street, NW, Washington, DC 20001; (202) 334
-
3213;
http://gulliver.trb.org/bookstore) (2006)
Comprehensive benefits packages with
financial incentives, services produce reduction
s in VMT of about 15%.

41
-
42

TRF/

congest

How Traffic Jams Are Made In City Hall
in
Reason
by Sam Staley and Ted
Balaker (Reason Foundation, 3415 S. Sepulveda Blvd., Suite 400, Los Angeles,
CA 90034; (310) 367
-
6109; http://reason.com/news/show/119192.html
) (April
2007) Five Ways o Reduce Traffic Congestion: (1) Expand capacity, (2) Better
management of the existing road network, (3) Market pricing for roads, (4)
Market pricing for parking, (5) Privatization.

43
-
44

TRF/

service
patrol

Identification of Cor
e Functions and Development of a Deployment Planning
Tool for Safety Service Patrols in Virginia

by Praveen K. Edara and Lance E.
Dougald, Virginia Transportation Research Council, 530 Edgemont Road,
Charlottesville, VA 22903 (Virginia Department of Transp
ortation, 1401 E.
Broad Street, Richmond, VA 23219) (Dec 2006) I
n urban regions, the operating
cost of SSPs are typically outweighed by the benefits the service provides to the
traveling public.

45
-
46

TRF/

congest

Rush Hour: How States Can Reduce Congesti
on Through Performance
-
Based Transportation Programs
by

Wendell Cox, Alan E. Pisarski and Ronald
D. Utt (Heritage Foundation, 214 Massachusetts Ave NE, Washington DC
20002
-
4999; ph 202.546.4400;
http://www.heritage.org/Research/SmartGrowth/bg1995.cfm) (Jan
uary 10,
2007)
Road investments are more cost
-
effective than transit investments.

47
-
48


TRANSPORTATION RESEARCH DIGEST

ARIZONA TRANSPORTATION INSTITUTE

e
-
mail
jsemmens@cox.net



MA
Y 2007



9

Best
-
Value Procurement Methods for Highway Construction Projects
, NCHRP Report 561

by
Sidney Scott, III, Keith R. Molenaar, Douglas D. Gransberg, Nancy C. Smith (Tra
nsportation
Research Board, 500 Fifth Street, NW, Washington, DC 20001; (202) 334
-
3213;
http://gulliver.trb.org/bookstore) (2006)



Highlights



The low
-
bid system may not result in the
best value for dollars expended or the best
performance during and afte
r construction.



Best
-
value procurement incorporates factors
other than just price into the selection
process to improve performance.



Use of best
-
value procurement in a variety
of different forms resulted in cost or time
improvements or both.


The majority

of public sector highway
construction contracts are awarded strictly on a
low
-
bid basis. Except under extraordinary
circumstances, the contractor submitting the
lowest responsive bid is awarded the
construction contract. While the low
-
bid
procurement syst
em has a long
-
standing legal
precedence and has promoted open
competition, a concern expressed by owners
and some of their industry partners is that a
system based strictly on the lowest price
provides contractors with an incentive to
concentrate on cuttin
g bid prices to the
maximum extent possible, even when a higher
cost product would be in the owner's best
interest. As a result, the low
-
bid system may
not result in the best value for dollars expended
or the best performance during and after
construction.

In today's construction climate, public
sector owners are finding themselves under
increasing pressure to improve project
performance, complete projects faster, and
reduce the cost of administering their
construction programs. In response to these
pressur
es, the industry has experimented with
alternative procurement and contracting
methods. More construction owners are
implementing one of these alternatives, best
-
value procurement, to improve project quality
and enhance performance. In essence, best
-
value
procurement incorporates factors other
than just price into the selection process to
improve performance or achieve other specific
project goals.

The research team identified best
-
value
procurement methods that have been
considered, developed, or used for
awarding
construction in the United States and
internationally. A comprehensive literature
review focusing on foreign and domestic
practices for a wide variety of construction
sectors was completed. The literature included
articles, reports, case studies,
and proposal or
bidding documents addressing a wide spectrum
of best
-
value procurement concepts. Case
studies from more than 60 best
-
value
procurement documents were reviewed.
Additionally, a national transportation agency
survey was conducted to help defi
ne the state
of best
-
value practice on highway construction
projects. Finally, to benefit from the vast
international experience with best
-
value
procurement, results from the 2004
FHWA/
AASHTO International Construction
Management Scan

research project wer
e
incorporated into this report.

The findings show a trend in public
sector construction toward the increased use of


10

various best
-
value procurement methods,
highlight some of the issues associated with the
traditional low
-
bid system, and provide
examples o
f how best
-
value procurement is
implemented. The national transportation
survey revealed that 66% of the 44 highway
agencies responding to the survey have some
type of experience with best
-
value selection,
but it was very limited and primarily in the area
of design
-
build project delivery. However, the
research revealed that certain sectors of public
construction, for example the federal sector,
have moved aggressively toward the use of
best
-
value procurement and have attempted to
measure its relative succes
s. Additional
findings of the literature review are provided as
follows:

o

The Federal Acquisitions Regulations
(FAR) include commentary regarding
how the low
-
bid method fails to serve
the public interest because the lowest
offer may not result in the lowest

overall cost to the public.

o

A recent Navy study comparing best
-
value procurement with traditional
methods points to a reduction in cost
growth from 5.7% to 2.5% and a
reduction in claims and litigation of
86%.

o

The General Services Administration
Public Bu
ilding Services procures
100% of its new buildings and
renovations through best
-
value
procurement.

o

A 1997 National Science Foundation
study concluded that design
-
build
contracts procured using the two
-
step
best
-
value procurement procedure had
the best cost

and schedule growth
performance, albeit representing a very
small average improvement over the
other procurement methods.

o

The 2003 Fall Meeting of the ABA
Forum on the Construction Industry
addressed Value
-
Based Contracting at
both the federal and state l
evels. The
central thesis of the program was that
best
-
value procurement was emerging
as a viable alternative to the traditional
low
-
bid method in public sector
construction, and practitioners need to
be prepared for this emerging trend.

o

A baseline of proj
ects and performance
results was compared with performance
outcomes for best
-
value highway
projects. The results indicated that the
use of best
-
value procurement in a
variety of different forms resulted in
cost or time improvements or both.

o

Legislation and

regulations for public
sector construction at the federal and
state levels are moving toward greater
use of contracting approaches to
achieve the best value for dollars
expended.


Many federal and state agencies have
implemented various source selection m
ethods
and have developed instructions or procedures
for development and implementation of these
methods.

TRANSPORTATION RESEARCH DIGEST

ARIZONA TRANSPORTATION INSTITUTE

e
-
mail
jsemmens@cox.net



MA
Y 2007



11

Riprap Design Criteria, Recommended Specifications, and Quality Control
, NCHRP Report 568

by P. F. Lagasse, P. E. Clopper, L.W. Zevenbergen, J. F.
Ruff, Ayres Associates Inc. Fort Collins,
CO (Transportation Research Board, 500 Fifth Street, NW, Washington, DC 20001; (202) 334
-
3213; http://gulliver.trb.org/bookstore) (2006)



Highlights



Design equations for sizing riprap are
evaluated with sensitivi
ty analyses.



Guidance on determining design variables
and design examples are provided for each
application.


This research accomplished its basic
objectives of developing design guidelines.
This study did not involve any original
laboratory experiments,
but some analysis
(specifically, one
-

and two
-
dimensional
computer modeling) was necessary to address
issues related to input hydraulic variables for
design. A fundamental premise of this study is
that riprap is an integrated system and as such,
successful

performance of a riprap installation
depends on the response of each component of
the system to hydraulic and environmental
stresses throughout its service life.

A review of the foreign and domestic
technical literature and a survey of practitioners
inclu
ding state DOT hydraulic engineers,
FHWA Resource Center and Division/District
engineers, and hydraulic engineers from other
federal agencies and consulting firms were
used to establish the state of practice in riprap
design for each of the applications at

the outset
of the study. The summary of current practice
in Chapter 2 is the basis for the interpretation,
appraisal, and application recommendations in
Chapter 3. Design equations for sizing riprap
are evaluated with sensitivity analyses using
laboratory

and/or field data, where available,
for the applications of interest to this study.
Based on the sensitivity analyses, a design
equation or design approach is recommended
for each application.

Sizing the stone is only the first step in
the comprehensive d
esign, production,
installation, inspection, and maintenance
process required for a successful riprap
armoring system. Filter requirements, material
and testing specifications, construction and
installation guidelines, and inspection and
quality control pr
ocedures are also necessary.
Specific criteria or approaches for these
requirements are developed for each riprap
application area.

Guidance on determining design
variables and design examples are provided for
each application. Design of riprap for
overtop
ping flow conditions on roadway
embankments and flow control
countermeasures is also considered. An
annotated description of riprap design software
and reference data sets for testing design
software or spreadsheets are included. Riprap
failure mechanisms
are identified as a basis for
developing inspection guidance, and selected
case studies of failures are used to emphasize
the need for post
-
flood/post
-
construction
inspection. In addition, concepts (but not
design guidance) for a bioengineering or hybrid
d
esign approach for bank stabilization using a
combination of rock and vegetative treatments
are discussed.

To guide the practitioner in developing
appropriate riprap designs and ensuring
successful installation and performance of


12

riprap armoring systems fo
r bankline
revetment, at bridge piers, and at bridge
abutments and guide banks, the findings of
Chapter 2 and the recommendations of Chapter
3 are combined to provide detailed guidelines
in a set of appendixes: Appendix C,
Guidelines
for the Design and Spe
cification of Rock
Riprap Installations

and Appendix D,
Guidelines for the Construction, Inspection,
and Maintenance of Rock Riprap Installations.


Conclusions

The intent of this study was to develop
a unified set of guidelines, recommended
specifications
, and procedures that can be
accepted by the state DOTs for the design,
installation, and inspection of riprap for a range
of applications, including at streams and river
banks, at bridge piers and abutments, and on
countermeasures such as guide banks. Thi
s
research effort is comparable in intent to the
recent work by the European Union that
resulted in adoption of a unified standard for
riprap that transcends geographic and
institutional boundaries. Specific conclusions
and recommendations are contained in

Chapter
4 for each of the functional areas investigated
for the riprap applications of interest to this
study:

o

Riprap design equations

o

Filter requirements

o

Material and testing specifications

o

Construction/installation guidelines

o

Inspection and quality co
ntrol

o

Other topics considered



TRANSPORTATION RESEARCH DIGEST

ARIZONA TRANSPORTATION INSTITUTE

e
-
mail
jsemmens@cox.net



MA
Y 2007



13

Guidelines on the Use of Underseals as a Pavement Moisture Barrier

by Cindy K. Estakhri and
Shiva Ramakrishnan, Texas Transportation Institute, Texas A&M University System, College
Station, Texas 77843
-
3135 (Texas Depart
ment of Transportation, Research and Technology
Implementation Office P.O. Box 5080, Austin, Texas 78763
-
5080;
979.845.1734;
http://tti.tamu.edu
) (Aug 2006)



Highlights



Excess water in a pavement structure can
overshadow many other pavement design
factor
s such as stress and strain,
deformation, volume change, and fatigue.



Underseals can be very effective in
protecting base materials from the intrusion
of surface water.


Records of experimental road tests have
documented that during periods when
pavements

contain large amounts of free water
the rates of deterioration range: from 10 or 20
up to hundreds and thousands of times greater
than during times when they contain little or no
free water. The effects of excess water in a
pavement structure can overshad
ow many other
pavement design factors such as stress and
strain, deformation, volume change, and
fatigue.

When base materials that contain more
than 5 to 10% fines (which are most of the flex
base materials in Texas) become saturated,
these bases will not
drain freely due to capillary
forces. If base materials are not designed to
drain freely, they should be protected from the
intrusion of surface water.

In most cases, water that enters a
pavement's structure comes through the
pavement surface. In those few

cases where
groundwater seepage is entering the pavement
structure, drainage provisions should be made
to intercept this type of water.

The infiltration of water through the
pavement surfaces depends on the global
permeability, which is affected by the mi
xture
type, density, and degree of cracking for
asphalt concrete (AC) pavements. For Portland
cement concrete (PCC) pavements, the global
permeability is affected by the condition of the
cracks and/or joints. A Federal Highway
Administration (FHWA) study o
f numerous
pavement sections found that 33 to 50% of the
precipitation water falling on an AC pavement
and 50 to 67% for PCC pavement could
infiltrate through the pavement surface to the
road base. One hundred percent of Texas
Department of Transportation
(TxDOT)
districts surveyed consider the primary function
of an underseal to be to serve as a moisture
barrier to prevent the intrusion of surface water
into underlying layers. Another function which
is considered important is that it enhances the
bond with

the subsequent pavement layer. A
few districts mentioned that they believed there
was a secondary benefit associated with
delayed reflection cracking and preventing the
movement of subsurface moisture into the
surface layer.

Underseals are used on all typ
es of
surfaces: existing hot
-
mix asphalt concrete
(HMAC), PCC, and aggregate bases. The most
common use is to apply an underseal to seal off
cracks in an existing pavement (PCC or AC)
prior to overlay. However, several districts
(about one
-
third of those s
urveyed) routinely


14

use an underseal any time a hot mix overlay is
placed.

The most common type of binder used
for seal coats applied as underseals is AC
-
20
-
5TR, and the most common aggregate grade is
Grade 4. Some districts select binder based on
specific
criteria (such as weather and traffic).
Both lightweight and natural aggregates are
used for underseal construction.

Testing and evaluation performed by
some districts prior to underseal and overlay
include coring (and visual evaluation of cores
for signs
of stripping), falling
-
weight
deflectometer (FWD), ground
-
penetrating radar
(GPR), ride quality, check pavement
management information system (PMIS)
scores, and perform visual evaluation to
determine if milling is required. Dense
-
graded
types C and D mixes

are the most common
surfaces applied over underseals.

The main problems or failures
experienced with underseals include: (1)
asphalt binder from the underseal bleeds
through to the surface of the overlay; (2)
underseals (on aggregate bases) sometimes get
damaged by traffic or construction operations
prior to overlay, allowing water to leak into the
base; (3) underseal traps moisture in a
moisturesusceptible layer causing it to fail.

Excessive binder application rates for
underseals can cause the binder to
bleed
through to the surface of the HMAC overlay.
This is true for both very high viscosity asphalt
binders, such as asphalt rubber, as well as low
viscosity binders. There is some evidence to
suggest that low viscosity binders (even when
applied at approp
riate application rates) have a
propensity for bleeding.

Poor construction and quality control
practices on the underseal can reflect through to
the performance of the HMAC overlay.

Underseals can be very effective in
protecting base materials from the int
rusion of
surface water. This is evidenced from failures
that occurred in areas where the underseal was
damaged prior to overlay. This has been a
problem in regions of the state with low rainfall
as well as high rainfall rates. The need for an
underseal ma
y be more a function of the
moisture susceptibility of the base material than
the region in which it is used.

Base materials should be adequately
cured prior to prime and surface treatment. This
helps to ensure a good bond of the surface
treatment and prev
ent highway traffic or
construction traffic from damaging the surface
treatment prior to overlay. Any damaged areas
should be repaired. Even small and isolated
areas associated with a damaged underseal
have lead to failure of the underlying base and
HMAC o
verlay.

While concern has been speculated over
underseals trapping moisture in underlying
layers that eventually leads to pavement
failures, researchers could find no evidence to
document this. On the other hand, there is
evidence to show that any moisture

susceptible
AC layer that is overlayed (even without an
underseal) has the potential to strip.

Concern has also be expressed that
when a seal is placed under an HMAC overlay,
water penetrates the HMAC and collects on top
of the underseal where it remains
until
evaporation. There is a fear that the action of
traffic in these conditions will accelerate
damage to the mix. In pavements where GPR
data were collected one day after a heavy rain
and which showed this situation to exist, these
pavement have perform
ed very well.

Because of the permeability associated
with most asphalt concrete pavements or their
longitudinal construction joints, rainfall will
penetrate through most overlays. Without an
underseal, this water will proceed to the
underlying layers.

GPR
data collected one day after a
heavy rainfall showed that moisture seems to
be penetrating the underseal on some
pavements. This could be due to cracking in the
underlying layer, damage which occurred to the
underseal prior to overlay, or that in some case
s
the underseal may be completely impermeable.

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15

I
-
70 Glenwood Canyon Overlay
w
ith Trinidad

Lake Asphalt/Steel Slag Hot Mix Asphalt

by
Robert Laforce
, Yeh and Associates, 5700 E. Evans Ave., Denver, CO 80222 (Colorado
Department of Transportation


Researc
h, 420 I E. Arkansas Ave., Denver, CO 80222) (Sep 2006)



Highlights



This study was unable to identify superior
performance of the TLA/steel slag mix.


Project NH 0702
-
217, constructed on 1
-
70 in Glenwood Canyon in 2001, was the first
use
-

of Trinidad La
ke Asphalt (TLA) in
combination with steel slag by the Colorado
Department of Transportation. To evaluate the
performance of the TLA modified pavement, a
three
-
year study was developed. By tracking
rutting, cracking and general pavement
condition through s
emiannual site evaluations,
researchers hoped to determine if the addition
of TLA and steel slag aggregate could improve
the performance of the pavement over
traditional mix designs.

For this project the entire two inch thick
hot mix asphalt (HMA) surface
was planed to a
depth of 1
-
1/2 inches and replaced with two
inches of Trinidad Lake Asphalt / steel slag
modified HMA. The job mix formula, which
called for asphalt cement of 6.5% ± 0.2% of the
total mixture by weight, utilized Koch PG 76
-
28 binder modifie
d with 25% TLA by weight
of the binder. The aggregate was crushed, with
100% of the particles retained on the #4 sieve
having 3 or more fractured faces, and this
requirement included 25% steel furnace slag by
weight. International Milling Service of Pueblo
,
Colorado supplied the slag. The mix design
included requirements for high mix
temperatures during production and placement,
as well as a minimum Hveem stability of 55
and low mix permeability.

For this evaluation, three 1,000
-
foot test
sections were sele
cted, two westbound and one
eastbound. In the westbound lanes, Section 1
developed severe alligator cracking associated
with the longitudinal joints, and Section 2 had
longitudinal cracks at or adjacent to the
centerline joint that extended completely
thro
ugh the test section. All of this distress was
in the area of the longitudinal joint, not in the
wheel path where damage from traffic normally
occurs. The location of the longitudinal and
alligator cracking lead to the conclusion that
the compaction in the

immediate area of the
longitudinal construction joint was inadequate.
The fact that the amount of cracking increased
yearly indicated that the condition of the
pavement in the area of the joint will continue
to deteriorate. The cracking is evidently the
r
esult of low joint densities allowing moisture
to penetrate and weaken the surface. An intense
sealing effort may prolong the life of the failing
joint; however, the danger of pop
-
outs
developing into potholes may require
replacement of the asphalt in the
near future.
The eastbound test section also developed
longitudinal cracking along the construction
joint in the first few months after construction.
However, subsequent site visits did not find
any additional cracking or deterioration of the
pavement. The

pavement in the eastbound test
section is in excellent condition and shows no
need of extensive maintenance.

Because the vast majority of distress
occurred in the area along the longitudinal
construction joint, the researchers felt that the
early failure
of the pavement was due to


16

inadequate construction joint densities caused
by high mix stiffness during compaction and
lack of mix resistance to repeated freeze
-
thaw
stress. The relatively good condition of the
surface away from the longitudinal joints and
the good performance of the eastbound test
section suggest that properly constructed the
TLA/steel slag mix can perform well.
Additional research is warranted to address
poor joint performance and heavy smoke
caused by the necessity for high mixing and
pla
cement temperatures.


Recommendations

Because this study was unable to
identify superior performance of the TLA/steel
slag mix to justify its higher cost, future use
should be an experimental feature in
conjunction with standard mix test sections
built to
allow performance comparisons. On
future studies, conventional CDOT mix test
sections should be included regardless of the
modifier or mix feature being evaluated.
Additionally, if the benefits of using only TLA
or steel slag are to be determined, future s
tudies
should compare conventional CDOT mixes
with asphalt mixes modified with only one
product at a time.


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17

Material Property Characterization of Ultra
-
High Performance Concrete

by Benjamin A.
Graybeal, PSI, Inc., 2930 Eskridge Road, Fairfax, VA 22031 (O
ffice of Infrastructure Research and
Development, Federal Highway Administration, 6300 Georgetown Pike, McLean, Virginia 22101
-
2296) (Aug 2006)



Highlights



Ultra
-
High Performance Concrete (UHPC)
displays significantly enhanced material
properties compare
d with other concrete.



Steam
-
based treatment of UHPC tends to
significantly enhance its material properties


Ultra
-
High Performance Concrete
(UHPC) is a new type of concrete that exhibits
properties of enhanced strength, durability, and
long
-
term stabilit
y. The objective of this
research was to evaluate the material
characteristics of UHPC for potential use in
highway bridge applications.


Conclusions

UHPC displays significantly enhanced
material properties compared with normal and
high
-
performance concret
e (HPC).

Steam
-
based treatment of UHPC tends
to significantly enhance its material properties.
Three steam
-
based treatments
-
steam, delayed
steam, and tempered steam
-
were investigated
and compared with UHPC that was not
subjected to a curing treatment after

casting. In
general terms, steam treatment increases
UHPC's compressive strength by 53%,
increases its modulus of elasticity by 23%,
decreases its creep coefficient from 0.78 to
0.29, and virtually eliminates long
-
term
shrinkage. Steam treatment also decr
eases
chloride ion penetrability to a negligible level
and significantly enhances abrasion resistance.
The enhancements of material properties
affected by the delayed steam and tempered
steam treatments are similar to those of the
steam treatment but of a
slightly lesser
magnitude.

UHPC exhibits very high compressive
strengths, regardless of the curing treatment
applied. Thus, steam treated UHPC can reach
its full compressive strength within 4 days after
casting.

The mixing time and rheological
properties o
f fresh UHPC are influenced by the
concrete mixer design, the ambient
environmental conditions in the mixer, and the
elapsed time since blending of the premix.
Older UHPC premix requires more mixing to
achieve the correct rheological properties,
likely due

to the agglomeration of fine particles
in the premix during storage.

The set time of UHPC is significantly
delayed compared with normal concrete; final
set does not occur until 12 to 24 hours after
casting. This time to set could also be longer
depending
on the admixtures and on other
constituents in the mix.

Once setting has initiated, UHPC gains
compressive strength very rapidly. If
maintained at normal laboratory temperatures,
UHPC compressive strength will increase to
over 70 MPa (10 ksi) by 2 days aft
er setting.
Subsequently, the rate of strength gain will
decrease; 97 MPa (14 ksi) will be reached by
10 days after setting.

The compressive strength of UHPC is
not affected by the specimen geometry used to
determine the result. In all cases, the


18

compressi
ve strength results did not vary by
more than 8%.

The curing conditions present during
and just after the setting of UHPC can
significantly affect the final properties of the
concrete. In the untreated case, concrete
cylinders that were stripped as final s
et was
being reached exhibited 25% lower 28
-
day
compressive strengths compared with those
stripped 1 day after setting was complete.

The tensile strength of UHPC, both
before and after tensile cracking, is
significantly higher than the strength that
occur
s in normal concrete.

The ASTM C496 split
-
cylinder tension
test, modified to capture first cracking,
provides the clearest indication of the tensile
cracking strength of UHPC.

The modulus of rupture defined by the
ASTM C1018 prism flexure test overestimat
es
the tensile cracking strength of UHPC by
approximately 60%.

The ASTM Cl018 prism flexure test
provides a clear means of comparing the post
-
cracking tensile behavior of various fiber
-
reinforced concretes. UHPC, regardless of
curing treatment, performed e
xceptionally well
according to the toughness indices defined by
this test.

UHPC displays durability properties
that are significantly beyond those normally
associated with concrete.

Exposing cracked UHPC split cylinders
to an aggressive environment did no
t result in
any noticeable decrease in the peak tensile
load
-
carrying capacity. The peak load
-
carrying
capacity of either steam
-
treated or untreated
UHPC did not have a discernable decrease after
cracking, thus indicating that the sodium
chloride solution
did not enter the cracks and
did not cause the fiber reinforcement to
deteriorate.

UHPC exhibits shrinkage behaviors that
are somewhat different from those of normal
concrete. In total, UHPC tends to exhibit
approximately 800 microstrain of shrinkage as
me
asured from casting through 1 year. Without
any curing treatment, UHPC will continue to
shrink at an ever
-
decreasing rate. Steam
treatment accelerates the shrinkage to such an
extent that the entirety of the shrinkage occurs
during the 2
-
day treatment, and

the UHPC is
then stabilized against further shrinkage. Also,
the total shrinkage in steam
-
treated UHPC
tends to be slightly higher than the asymptotic
shrinkage approached by untreated UHPC.

Large compressive stresses on relatively
low
-
strength UHPC can c
ause significant short
-
term creep. This situation is akin to the
stressing of prestressed girders. The creep that
occurred over this short load duration indicates
that the total long
-
term creep of UHPC loaded
at this compressive strength would be much
high
er than that observed in the long
-
term
creep testing.



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19

Benefits Estimates of Highway Capital Improvements with Uncertain Parameters

by James H.
Lambert and Nilesh N. Joshi, Virginia Transportation Research Council, 530 Edgemont Road,
Charlottesville, V
A 22903 (Virginia Department of Transportation, 1401 E. Broad Street,
Richmond, VA 23219) (Sep 2006)



Highlights



The project developed software to provide
the DOT with additional methodology for
benefits estimation, which the agency can
use to distinguis
h among candidate projects.



The methodology will allow identification
of highway projects with the highest value
-
to
-
cost ratios.


This effort has demonstrated an
assembly of methodologies for the estimation
of the benefits of crash reduction, travel time
savings, emissions reduction, fuel savings, and
service of heavy trucks that are anticipated
from road improvement projects. The
methodologies have been applied to 53
candidate projects from the Northern Virginia
district from 2005 and the results have bee
n
compared to those of a prioritization
methodology that is currently implemented by
VDOT.

Use of interval analysis for uncertainties
of the parameters, such as the crash reduction
factor, the value of travel time savings, the
reduction in volume
-
to
-
capaci
ty ratio, etc.,
allows the estimation of benefits to proceed in a
situation of sparse or uneven data about the
candidate projects. The interval analysis can
highlight situations where data are sufficient
for prioritization, or situations where additional
d
ata are needed.

The methodology for the estimation of
maintenance and other life
-
cycle costs has also
been reviewed. The review suggests that
maintenance and other life
-
cycle costs may be a
constant proportion of the equivalent annual
capital costs, and fu
rthermore may be
considered to be uniform across the candidate
projects absent additional project
-
specific
information. That is, this assumption could be
justified either if (1) all projects are the same
type
--

e.g., lane widening as opposed to transit
im
provements or signal coordination, both of
which should have higher proportions of
maintenance costs; or (2) the data are
sufficiently lacking that it is needed to use a
uniform factor/assumption to estimate
maintenance costs.


Recommendations

The highway
agency can complement
its existing score
-
based prioritization system
with methodologies for the estimation of the
anticipated benefits of candidate projects.

The benefits can be estimated in several
categories, e.g., safety, congestion,
environment, and ec
onomic development.

The benefits can be monetized, but it
may be preferable to keep them in their natural
units, and/or to present the monetized and non
-
monetized benefits side by side.

A straightforward interval
-
type
presentation of parameter uncertainti
es should
be used to enable assessments of benefits to
proceed when critical information about
particular projects is awaited. Eventually, the
default values of uncertain global parameters
(e.g., improvement in vehicle speed, k
-
factor
for percentage of tra
ffic in the peak period,
reduction in volume
-
to
-
capacity ratio) should


20

be reconsidered in favor of calculated values
for each project or category of project.

The assumptions and
-
data inputs used
in the estimation of project benefits should as
much as possi
ble be transparent to decision
-
makers, engineers, agency executives,
legislators, and members of the public.

Consideration of additional categories
of benefits, e.g., variance of travel times,
emergency and evacuation, intermodal
efficiencies, economic dev
elopment,
environmental protection, and quality of life,
should proceed as the state of the practice of
benefits estimation evolves.

The additional benefit category of the
"avoided cost of a lost or missed opportunity,"
such as a failure to purchase a righ
t of way
where development is imminent, should be
explored.

The methodology should be considered
for use in prioritizing the allocation of
resources within dedicated funds for smaller
projects of particular types, e.g., signal and
timing improvements, grad
e crossing safety,
the Congestion Mitigation and Air Quality
(CMAQ, which are projects such as turn lanes
and signals, based largely on reductions in
emissions volume), Regional Surface
Transportation Program (RSTP), the National
Highway System Funds (larg
ely interstate), and
the Urban Programs (prerogative of localities).
In this vein, the MPOs have a quantification
method for RSTP funds, similar to methods
illustrated in this report. For NHS programs,
there is no such methodology
-
some factors are
quantifi
ed and some are not, and judgment is
used to combine them. The urban funding is
decided within the cities. The purveyors of the
disparate funding programs identified above
should be exposed to the methods of this report
and encouraged to adopt the features

(interval
analysis where assumptions of parameter
values should be nonspecific, monetized versus
nonmonetized, disaggregation of benefits, etc.)
that may be appropriate programs.

Prioritization methodology with which
to support the removal of already sele
cted or
ongoing projects from a construction program
should be considered.

Validation of the anticipated benefits
against what benefits are actually realized from
completed projects should proceed with the
help of the methodologies that are explored in
thi
s report.

MPOs and localities (cities) have their
own existing methodologies for quantifying the
performance of projects and prioritizing them.
The MPOs and localities should be exposed to
the methods developed in this report and
encouraged to select what
features and
sophistication that are most appropriate to their
circumstances. There is at present a variety of
degrees of rigor and sophistication in such
methods across Virginia MPOs and localities.


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21

Comparison of Virginia's Multimodal Transportation Co
rridors Using Cost and Demographic
Analyses

by James H. Lambert, Alexander S. Linthicum, and Shadi M. Wadie, Virginia
Transportation Research Council, 530 Edgemont Road, Charlottesville, VA 22903 (Virginia
Department of Transportation, 1401 E. Broad Street
, Richmond, VA 23219) (Sep 2006)



Highlights



Transportation planning agencies should
work toward the goal of accurately
quantifying benefits, thus enabling the use
of proper cost
-
effectiveness and cost
-
benefit
methods of analyses.


This report demonstra
tes the cost and
demographic components of an analytical
framework that will ultimately be useful for
comparing statewide multimodal plans and
policies in multi modal corridors. The
framework may ultimately encompass
demographic, behavioral, infrastructura
l,
environmental, institutional, land use, cost
-
efficiency, and other characteristics. The report
illustrates how multiple sources of data can be
used to compare needs and opportunities of
Virginia's eleven statewide multimodal
corridors based on selected
cost and
demographic characteristics.


Cost Analysis

The monetized costs can be used to
compare investments across transportation
modes and corridors; however, benefits must
plausibly be the same when comparing
transportation alternatives using only this
m
easure. It was outside the scope of this study
to make this determination.

If benefits are not judged to be
equivalent, they should be quantified, instead
of using the cost estimates alone as a surrogate
for cost
-
effectiveness. If benefits can be
quantifie
d, cost effectiveness analysis, which
compares life
-
cycle costs with quantifiable,
non
-
dollar benefits, or benefit cost analysis,
which compares life
-
cycle costs with dollar
-
quantifiable benefits should be used.
Transportation planning agencies should work

toward the goal of accurately quantifying
benefits, thus enabling the use of proper cost
-
effectiveness and cost
-
benefit methods of
analyses.

Cost estimates should include all costs
incurred during the system life
-
cycle. Modal
agencies and MPO/PDCs did not

have
operations and maintenance costs for many
projects, and without this information reliable
cost
-
analysis cannot be undertaken.

Greater cooperation is needed among
MPOs/PDCs to provide long
-
range
transportation plans in consistent formats.
MPOs/PDCs sh
ould strive to conform to a
single standard in terms of content, basis, and
format. All plans should contain lists of both
"programmed" (fiscally constrained) and
"vision" (fiscally unconstrained) projects.

The state cost estimations for interstates
tend t
o be higher than those from the regional
plans. This discrepancy should be investigated
further to determine the cause. And finally,
increased coordination between state and modal
transportation authorities, and also between the
state and regional planning

organizations will
be useful to proceed toward an integrated,
multimodal statewide transportation system.

A common pitfall of analyses in these
topics is inadvertently fitting the goal to the
available data. One might consider that the cost


22

analysis did e
xactly that: using various capital
costs as a basis of the study because they were
readily available. Overall, of course, to point to
the lack of available data to derive accurate
cost estimates for all of these projects is
progress itself. The effort desc
ribed in this
report is best considered to be a starting point
for determining the data needs and
opportunities for coordinating data acquisition
of multiple modal agencies. The exploration of
multiple sources of data in the cost analysis
should not be con
sidered to be a quantitative
comparison of whether Virginia should invest
in the highway only or multimodal alternatives.


Demographic Analysis

As greater population densities are
required for supporting alternative
transportation modes, those corridors
co
nnecting areas of significant densities are
best suited for multimodal transportation
investments.

The literature suggests that preliminary
work has been done to identify what thresholds
of populations density qualify a region for
particular types of multi
modal improvements,
but additional effort is needed to relate the
demographic analysis to these thresholds, in
particular to distinguish areas of supported and
unsupported needs for transit, rail, and other
modes.


Recommendations

State and regional agenci
es need to
develop a common method for developing
capital cost estimates when the project itself
has not been defined. Second, state and
regional agencies need to develop a common
method for including maintenance and
operating costs in these projects. The
fact that
some of these projects have different durations
increases the need for such a common method;
clearly, for example, the duration of improved
transit service and the duration of a lane
addition will be different. Once a common,
defensible approach
can be developed for
considering capital, maintenance, and operating
costs, then it should be easier to compare the
life
-
cycle costs of diverse projects.

In the area of demographic analysis,
further effort could characterize the corridors as
strong or weak

candidates for multimodal
passenger investment. Freight statistics such as
origins and destinations, volumes and
capacities, and shipping costs should be studied
for consideration of multimodal freight
investments. In addition, this population
density stu
dy can be combined with statewide
origin and destination flows to determine
statewide accessibility ratios. These ratios can
show the relative ease of transportation by a
particular mode from origin to destination at a
statewide scale. Investing in local m
ulti
-
modal
solutions will allow and encourage use of
statewide multimodal transportation options.
Travelers are more likely to involve a train or
bus on a long
-
distance trip if they know they
will not require an automobile once they get to
their destinatio
n.


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23

Rural Expressway Intersection Surveillance for Intersection Decision Support System

by Lee
Alexander, Pi
-
Ming Cheng, Max Donath, Alec Gorjestani, Arvind Menon, Bryan Newstrom, Craig
Shankwitz, Nic Ward, and Ray Starr

in Transportation Research Record

1944

(Transportation
Research Board, 500 Fifth Street, NW, Washington, DC 20001; (202) 334
-
3213;
http://gulliver.trb.org/bookstore) (2006)



Highlights



30% of all vehicle crashes in the United
States occur at intersections.



Poor gap acceptance on the par
t of the driver
is the primary causal factor in approximately
60% of rural through
-
stop, right
-
angle
intersection crashes.



An intersection decision support (IDS)
system design has been developed.


More than 30% of all vehicle crashes in
the United States
occur at intersections; these
crashes result in nearly 9,000 annual fatalities,
or approximately 25% of all traffic fatalities.
Moreover, these crashes lead to approximately
1.5 million injuries per year, accounting for
approximately 50% of all traffic inj
uries.

To clearly define the rural intersection
crash problem, an extensive review of both the
Minnesota crash database and research reports
quantifying the national problem was
undertaken. Crashes at rural expressway
through
-
stop intersections have simila
r crash
and severity rates when compared with all rural
through
-
stop intersections. However, right
-
angle crashes (which are most often related to
gap selection) were observed to account for
36% of all crashes at the rural expressway
intersections. At rural

expressway intersections
that have higher than expected crash rates,
approximately 50% of the crashes are right
-
angle crashes. Further investigation also found
that drivers' inability to recognize the
intersection and consequently to run the stop
sign was

cause for only a small fraction of
right
-
angle crashes. Gap selection is the
predominant problem.

That is consistent with other findings;
the primary causal factors for drivers who
stopped before entering the intersection were as
follows:

1. The driver lo
oked but did not see the
other vehicle (62.1 %), 2. The driver misjudged
the gap size or velocity of the approaching
vehicles (19.6%), 3. The driver had an
obstructed view (14.0%), or 4. The roads were
ice covered (4.4%). Of these four driver errors,
the f
irst three can be described as either
problems with gap detection or gap selection.
Recent crash analyses have shown that in these
states, poor gap acceptance on the part of the
driver is the primary causal factor in
approximately 60% of rural through
-
stop
, right
-
angle intersection crashes.

Given the extent of the crash problem
and the causal factors, an intersection decision
support (IDS) system design has been
developed based on the following design
factors:

In most rural through
-
stop crashes, the
driver
has obeyed the stop sign. This implies
that the driver is cognizant of his or her
situation and that the driver interface used at
the intersection is likely to capture the driver's
attention. This is a significant departure from
the signal/stop sign violat
ion problem, in which
the intervention system has to both capture the
driver's attention and convey a timely message


24

with substantial authority that a violation is
imminent if a proper response is not executed.

With the premise that the driver's
attention
has been captured, the IDS system
will provide a driver with timely, relevant
information concerning unsafe conditions. The
purpose of the system is to provide this
information as a means to enable a driver to
make a safer decision concerning gap
acceptanc
e, but not make the decision for the
driver. A prohibitive reference frame (i.e.,
telling a driver when not to go) is used to lessen
liability issues involved with indicating to a
driver when it is safe to go.

Given the increasing traffic volumes on
rural
expressways and traffic engineers' need to
maintain or increase capacity on these roads,
the IDS system should not stop traffic on the
main road. The IDS system should provide
some of the safety benefits of a signal
-
controlled intersection without the adve
rse
effects on main
-
line capacity, throughput, and
congestion.

The Minnesota Department of
Transportation (Minnesota DOT) and the
University of Minnesota are developing a
technology
-
based approach to solving the gap
acceptance problem for rural intersectio
ns. This
rural IDS system is designed to provide a driver
with the information needed to make correct
decisions about the available gap. The system
is designed to provide some of the safety
benefits of a signalized intersection (fewer
crashes, opportunitie
s for all drivers to enter or
cross the traffic stream, etc.) while minimizing
the downsides (expense of installation,
disruption of traffic flow, etc.). It should be
noted, however, that the IDS system will not
provide additional opportunities for drivers

to
enter or cross the traffic stream, because unlike
a traffic signal, it will not create gaps that were
not already there.

The surveillance system uses sensors,
computer processors, a communication
network, and a geometric representation of the
roadways
to determine the "state" of the
intersection. Main
-
line state information
includes the position, speed, (derived)
acceleration, and lane of travel of each vehicle
in the surveillance zone. This state information,
combined with known intersection geometry,
facilitates the real
-
time tracking of traffic gaps
on the main line. Minor road state information
includes the position and speed of the vehicle
on the minor road and an estimate of the
classification of the vehicle. Present
classification separates vehicl
es into four
categories: motorcycles and passenger cars;
sport utility vehicles and light trucks; medium
-
duty trucks and school buses; and heavy
-
duty
trucks, semi and motor coaches, and farm
equipment.

The state information provides the basis
with which t
o assess threats to drivers waiting
to cross or enter the main
-
line traffic stream. In
addition to intersection state data, the threat
assessment algorithms may use parameters,
including driver demographic information
(potentially available wirelessly), ro
ad
condition information (from weather and road
sensors mounted at or near the intersection),
and vehicle information (model, performance
parameters, etc., potentially available
wirelessly).

The IDS system is designed so that
should an unsafe condition be
detected by the
threat assessment algorithm, the central
processor initiates the proper warning to the
driver through an infrastructure based interface
known as the driver
-
infrastructure interface
(DII). The design of the DII has not yet been
finalized; wo
rk continues to finalize a design
that is acceptable to state departments of
transportation and the National Committee on
Uniform Traffic Control Devices.


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25

Trade
-
Offs Between Security and Inspection Capacity: Policy Options for
L
and Border Ports of
Entry

by Hilma Villegas, Patrick L. Gurian, Josiah M. Heyman, Adrian Mata, Robert Falcone,
Edward Ostapowicz, Steven Wilrigs, Michael Petragnani, and Eric Eisele

in Transportation
Research Record 1942

(Transportation Research Board, 500 Fifth Street, NW, Washin
gton, DC
20001; (202) 334
-
3213; http://gulliver.trb.org/bookstore) (2006)



Highlights



More stringent inspections create substantial
delays.



Current inspections appear to be largely
cursory.



Diverting more traffic into the Secure
Electronic Network for T
ravelers Rapid
Inspection (SENTRI) program appears a
reasonable compromise solution.


Since the terrorist attacks of September
11, 2001 (9/11), international ports of entry are
increasingly seen as a means to protect against
the entry of terrorists to the

United States. At
the same time, land border ports of entry are
often key nodes in regional traffic networks.
Delays at ports of entry can propagate
throughout the region and contribute
significantly to overall congestion
-
related
delays. A study of the El

Paso, Texas. and
Ciudad Juarez, Mexico border region found
that closure of one of three regional ports of
entry would create queues extending onto a
major interstate highway, resulting in a 29%
increase in regional transit times.

While concerns about terr
orism have
changed the discourse about the border,
substantively changing operational procedures
at ports of entry, is a tremendous challenge, and
it is not clear that real progress has been made.
In the immediate aftermath of September 11,
there appears t
o have been a policy requiring
inspectors to open one compartment of each
vehicle, plus other possible measures, although
for security reasons the details of inspection
policies cannot be publicly confirmed by U.S.
Customs and Border Protection. These more

stringent inspections created substantial delays
at ports of entry. At the El Paso
-
Ciudad Juarez
ports of entry, waits of several hours at border
crossings were common in the fall of 2001. The
heightened security combined with the
recession to lower total

northbound automobile
crossings substantially in September 2001. The
border delays imposed a hardship on local
residents, many of whom cross the border
frequently for work, for education, or to visit
family members. Inspections appear to have
relaxed subs
equently, and border wait times for
2004
-
2005 are usually 30 min or less. This
suggests that the policy of more detailed
inspections yielded to the needs of the local
community.

The results presented suggest that there
are no easy solutions to this situati
on. Current
inspections appear to be largely cursory and
provide little time for such a large fraction of
the entering vehicles that effective inspections
would not appear to be possible. Two
approaches to allowing more detailed primary
inspections were co
nsidered in this study
--
placing a ceiling on the amount of time in
primary inspections and diverting more traffic
into the Secure Electronic Network for
Travelers Rapid Inspection (SENTRI) program.
Both approaches would require major
operational changes fr
om existing practices,
changes that may not be feasible. Limiting the


26

time in primary inspections would dramatically
increase the number of secondary inspections.
Increasing the SENTRI program manyfold
would require a much lower fee to attract
sufficient e
nrollment and the construction of
dedicated inspection facilities at the Bridge of
the Americas and Ysleta ports of entry. Even
combining these approaches, it would be
difficult to achieve 100% high
-
attention
inspections. (For the Paso del Norte port of
en
try, roughly a fourfold increase in the
SENTRI program and a sevenfold increase in
secondary inspections would be required.)

This situation suggests that the trade
-
offs between depth of inspections and
throughput, described at the start of this paper,
are
likely to be a persistent issue in port
management. Requiring high
-
attention
inspections roughly doubles the inspection time
(from 34 to 70 s) with a corresponding decrease
in the throughput capacity of the port. Higher
levels of overcapacity must be toler
ated to
permit longer inspection times. Under current
conditions, the use of exclusively high
-
attention inspections would cause demand to
exceed the Paso del Norte's processing capacity
by nearly a factor of two. An inspection time of
51 s (the case when h
igh
-
attention primary
inspections are limited to 63 s or less) would
cause demand to exceed capacity by nearly
50%. If 50% of normal, noncommercial
crossers can be enrolled in the SENTRI
program (this would require most of the people
who cross on a weekly
or more frequent basis
to enroll in the program), then shifts to high
-
attention inspections in non
-
SENTRI lanes will
be much less disruptive. (At a 5
-
s primary
inspection time. demand would not exceed
capacity; at a 70
-
s inspection time. demand
would excee
d capacity by about 15%.)

The absence of a single, definitive
solution to this problem should not discourage
incremental efforts to improve the situation.
Both diverting more problematic cases to
secondary inspections and increasing the use of
the SENTRI p
rogram are amenable to
incremental implementation as they do not
require the construction of new infrastructure
or development of new programs. For example,
port managers could increase efforts to
publicize the SENTRI program or work to
reduce the enrollme
nt fee. Managers also could
give guidance to primary inspectors to avoid
lengthy primary inspections and refer
marginally more vehicles to secondary
inspections. Although the goal of 100% high
-
attention inspections may not be feasible, even
partial impleme
ntation of these options would
allow for the proportion of high
-
attention
inspections to be increased from its current
value of 21%.

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27

Structural Behavior of Ultra
-
High Performance Concrete Prestressed I
-
Girders

by Benjamin A.
Graybeal, PSI, Inc., 2930 Esk
ridge Road, Fairfax, VA 22031 (Office of Infrastructure Research and
Development, Federal Highway Administration, 6300 Georgetown Pike, McLean, Virginia 22101
-
2296) (Aug 2006)



Highlights



Ultra
-
High Performance Concrete is a viable
substitute for other c
oncrete in prestressed I
-
girders.


Ultra
-
High Performance Concrete
(UHPC) is a new type of concrete that exhibits
properties of enhanced strength, durability, and
long
-
term stability. The objective of this
research was to evaluate the potential use of
UHP
C in highway bridge girders. This
objective was achieved through full
-
scale
structural testing of UHPC American
Association of State Highway and
Transportation Officials (AASHTO) Type II
bridge girders.

The research included an experimental
phase and an an
alytical phase. The
experimental phase focused on determining the
structural behavior of UHPC prestressed I
-
girders by completing full
-
scale girder tests.
The tests included one flexure test on a 24.4
-
m
(80
-
foot) girder and three shear tests on shorter
spa
n girders. These girders did not contain any
mild steel reinforcement; thus, the UHPC was
required to carry all secondary (i.e., shear,
temperature, shrinkage) tensile forces. The
analytical phase of this research analyzed and
elaborated upon the results f
rom the
experimental phase. This phase included
developing a rational philosophy for the flexure
and shear design of prestressed UHPC I
-
girders.


Conclusions

UHPC is a viable substitute for normal
concrete and high
-
performance concrete (HPC)
in prestressed

I
-
girders.

UHPC I
-
girders can be designed to
more efficiently carry flexure and shear forces.
A conservative estimate of the full UHPC
tensile and compressive stress
-
strain behavior
could be used to predict the flexural capacity of
an I
-
girder. A conserva
tive estimate of the post
-
cracking tensile capacity could be used to
predict the diagonal tensile capacity of UHPC
in the shear region of a girder.

Placing UHPC in an I
-
girder formwork
can be completed very rapidly with little need
for supplemental vibrati
on. UHPC was
observed to be nearly self
-
placing. The ability
of UHPC to be reinforced internally by fiber
reinforcement allows for the reduction or
elimination of most mild steel reinforcement,
which greatly simplifies the I
-
girder formwork
preparation. Wi
thout taking any special
precautions to release the formwork during
setting, no shrinkage cracks were observed in
the girders.

The shear capacities of UHPC
AASHTO Type II girders that did not contain
any mild steel shear reinforcement or any
draped prestre
ssing strands were between 1,690
kN and 2,225 kN (380 kips and 500 kips).
Traditional shear failure of the girder web
without any strand slippage occurred in one
girder at 2,225 kN (500 kips). Two other
girders failed at lower loads due to strand
slippage
and to horizontal debonding of the


28

web from the bottom flange, which resulted
from a preexisting defect.

The live
-
load flexural capacity of a
UHPC AASHTO Type II girder containing
twenty
-
four 12.7
-
mm, 1,860
-
MPa (0.5
-
inch,
270
-
ksi) prestressing strands was
4,370 kN
-
m
(38,700 kip
-
inches). This increased flexural
capacity compared with normal concrete and
HPC is primarily the result of the sustained
post
-
cracking tensile capacity of UHPC.

The failure of bridge girders composed
of UHPC was observed to be precip
itated by
the pullout of fibers that were bridging tension
cracks in the concrete. Flexural failure of an
AASHTO Type II girder occurred when the
UHPC at a particular cross section began to
lose tensile capacity due to fiber pullout. This
loss of the UHPC
tensile capacity necessitated
the transfer of those internal flexural tensile
forces onto the prestressing strands,
culminating in the rupture of the strands. The
traditional shear failure of a similar girder also
was caused by the loss of tensile capacity

of the
UHPC due to fiber pullout. In this loading
configuration, the girder could not redistribute
the tensile shear forces through any other load
path; thus, the girder rapidly lost 'all load
-
carrying capacity. A different girder's shear
failure in combi
nation with strand slip
demonstrated that fibers tend to pull out
gradually over a short timeframe and that in the
presence of an alternate load path the girder can
continue to maintain some 10ad
-
ca1Tying
capacity.

UHPC that is subjected to large tensile
s
trains will exhibit tightly spaced cracking in a
restrained region of a structural member. Crack
spacing as small as 3 mm (0.125 inch) was
observed during the structural testing of bridge
girders. The tensile flange of a prestressed
girder allows for the v
ery tight crack spacing
due to the prestressing strands ensuring tight
cracks and allowing for the redistribution of
some local strain irregularities. The web region
of an I
-
girder is sufficiently restrained by the
top and bottom flanges to exhibit relativ
ely
tight crack spacing, but the web region spacing
is not as tight as that in the tension flange under
flexural loading.

The development length of 12.7
-
mm,
1,860
-
MPa (0.5
-
inch, 270
-
ksi) low
-
relaxation
prestressing strands in UHPC is less than 0.94
m (37 i
nches). The AASHTO Type II girder
shear tests indicate that in a heavily distressed
shear region, the prestressing strands will
rupture after only minimal slip if they are
embedded at least 0.94 m (37inches) into the
UHPC.


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29

HOT Lane Buffer and Mid
-
Point
Access Design Review Report

by Carter Burgess in association
with Wilbur Smith Associates; The Resource Group; Perteet; EnviroIssues; IBI Group; Demich
Consulting (Washington State Department of Transportation, Planning and Programming Service
Center, Rese
arch Office, Olympia, Washington 98504
-
7370) (Oct 2006)



Highlights



The purpose of this report is to provide an
overview of buffer and midpoint access
designs for concurrent flow, high occupancy
toll (HOT) lanes that are either in operation
or under stud
y and to recommend the
preferred buffer and access designs for these
facilities.


HOT lanes are dedicated to transit,
carpools and vanpools, but also allow solo
drivers to use the facility for a toll when surplus
capacity is available. With the applicatio
n of a
HOT lane facility, a single occupant vehicle
(SOV) can choose to pay for the use of the
surplus capacity in the lanes. Tolls are adjusted
to ensure that these lanes keep flowing even
when the regular lanes are congested.


Recommendations


Buffer and

Inside Shoulder Width

Where feasible, a buffer
-
separated
facility should have a separation width of 4 feet
between the HOT/HOV lane and the adjacent
general purpose lane.

A continuous inside shoulder of 14 feet
is desirable for enforcement and to serve a
s a
breakdown lane. The minimum section should
provide at least a 2
-
foot buffer (except at access
points) and a 2
-
foot inside shoulder to separate
the travel lane from any barrier if installed. An
enforcement/breakdown area should be a
minimum of 10 feet w
ide.


Access Point Location

Access points should be located so that
there is a distance of between 500 and 1,000
feet or more per lane change required to move
from a ramp to the managed lane or vice versa;
the higher number being the desired distance
and t
he lower number being the minimum.


Access Point Length

Access to or from the HOT/HOV lane
should be consistent with the above guidance,
providing at least the minimum acceptable
distance per lane change to set the access point
length for each movement. Fo
r a combined
access (allowing both ingress and egress), the
length of the access point should be at least
twice the minimum acceptable lane change
distance.

The decision to provide an access
length of less than 1,000 feet should be
carefully studied for sa
fety and effectiveness.


Access Point Design

The ideal access point design will
provide separate locations for ingress and
egress. Between the managed lane and the
general purpose lane, an auxiliary lane will be
provided to allow vehicles to accelerate or
decelerate as appropriate. Immediately
downstream of the access point an enforcement
shoulder should be provided to allow
enforcement officers to monitor access to the
managed lanes.

Often insufficient right of way or
distance between interchanges exists t
o provide


30

the ideal solution. In such cases, access points
can be combined to allow ingress and egress at
the same point and if necessary or desired, the
auxiliary lane can be removed.

At a minimum the striping will change
from the prohibited buffer "doubl
e white
stripe" to permissive skip white striping.


Final Considerations

While the recommendations included in
this study represent the state of the practice, it
is important to note that they are the "best
available" based on recent experience.
Extensive
research designed to definitively
identify the impacts of the different designs
does not exist, particularly regarding access
design where physical constraints often
determine the type of access (combined, vs.
separate, whether a weave lane is provided,
et
c.). In existing facilities, every effort is made
to adequately balance the desire for high levels
of service in the managed lanes with providing
safe and efficient access and separation options.

The design recommendations provided
are based on previous sy
stem experience,
engineering judgment, and where existing,
results of applicable research. The appropriate
design for any new or converted managed lane
will vary based on field specific conditions
including existing right
-
of
-
way, available
pavement width,
design traffic volumes, facility
type, traffic mix, etc. These explanations are
intended to assist the engineer using these
guidelines in making adjustments, as
appropriate, for the specific project being
designed.

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31

The Price Is Wrong: Why Our Roads Are S
o Clogged

by Joseph Giglio (
TCS Daily
,
http://www.tcsdaily.com/; http://www.tcsdaily.com/article.aspx?id=021307C) (Feb 13, 2007)



Highlights



White House is promoting congestion
pricing for highways.



Congestion pricing allows consumers to
decide whether t
he price charged for a given
trip is worth their travel time savings.



We can charge motorists for using roadways
without forcing them to stop at toll
-
booths.



TexasDOT has been aggressive in pursuing
congestion pricing.


The Bush administration has asked
C
ongress for $175 million for state and local
governments to reduce traffic congestion, in
addition to the $105 million earmarked last
year. One of the White House's marquee
projects is congestion pricing, or charging
motorists a fee for using a particular
roadway
based on its traffic volume at any given minute.

Congestion pricing is economics at its
best. For decades, economists have championed
market
-
oriented solutions to highway problems
as a means to allocate scarce resources.
Congestion pricing gives c
onsumers the
opportunity to decide when it is in their
economic interest to ride crowded roads, and
whether the price charged for a given trip is
worth their travel time savings.

In the former Soviet
-
bloc states, the
standard way to allocate scarce goods w
as to
set the purchase price low enough for everyone
to afford, but to make consumers wait in long
lines to buy them. The real price depended on
what value consumers placed on their time.

This approach is the way we've always
allocated access to most road
ways in capitalist
America
-

access is "free," just like for a public
park. But our real cost skyrockets when we
consider the time we spend crawling along in
bumper
-
to
-
bumper traffic and with no option to
pay extra for a faster trip.

And even without facto
ring in the cost
of time frittered away listening to satellite
radio, highways have never really been "free,"
but subsidized by taxpayer dollars. Congestion
pricing is not a tax increase, but a user fee,
which is a better way to divide costs. Indeed,
econo
mists across the political spectrum have
long waxed enthusiastic about the superior
logic of levying market
-
based prices for access
to roadways; but until recently it remained little
more than an interesting classroom concept
since there was no practical w
ay to charge
motorists directly.

The advent of electronic toll collection
technology changed all this. Now we can
charge motorists for using roadways without
forcing them to stop at toll
-
booths, or even
slow down. Just as consumers are billed for
water, el
ectric power, cooking gas, and other
essential utilities, motorists would pay
according to how many miles they travel, how
large a vehicle they're driving, how much air
pollution they generate, and whether they're
subject to certain physical or economic
di
sadvantages that entitle them to special
discounts. This can be especially important for
commercial vehicles where time saved
translates into fewer operating costs. And let's
remember that the main purpose of surface
transportation is to facilitate and enh
ance
economic activity.

Congestion pricing means true
consumer sovereignty, while liberating the


32

roadway system from dependency on already
inadequate revenue sources, like motor vehicle
fuel taxes, and construction grants from the
Federal Transportation Tr
ust Fund. Not least of
all, it's an opportunity to improve the efficiency
of our roadway systems.

Here's one scenario: A state government
deeds an independent commercial enterprise
the rights for all roadways in its largest
metropolitan region. The enterp
rise would
support itself by implementing variable rate
user prices on the region's limited access
highways. These prices would be designed to
generate sufficient revenue to cover the costs of
operations, maintenance and expansion to keep
pace with rising
travel demand generated by a
growing economy

while offering a
competitive return on the initial investment.

Some corporate bodies like the Texas
Department of Transportation have already
started to work out a few of the most obvious
kinks. That is, without

any competition to hold
down prices, the natural instinct of the
enterprise's private owners would be to charge
motorists the highest possible rates while
providing the least amount of service.

So, the answer is to introduce a
competing agenda

namely, th
e one
represented by the same state and local
governments that are going to be getting the
federal government's funding windfall. They're
not interested in maximizing profits, but in
winning votes by providing lots of service
while keeping user charges as
low as possible.
Giving both the private and public sectors a
share of the common good assures fiscal
responsibility and good service at reasonable
prices.




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33

Using Archived AVL
-
APC Data to Improve Transit Performance and Management
, TCRP Report
113

by
Peter G. Furth, Brendon Hemily, Theo H. J. Muller, and James G. Strathman
(Transportation Research Board, 500 Fifth Street, NW, Washington, DC 20001; (202) 334
-
3213;
http://gulliver.trb.org/bookstore) (2006)



Highlights



Automatic data collection can revo
lutionize
schedule planning and operations quality
monitoring as agencies shift from methods
constrained by data scarcity to methods that
take advantage of data abundance.


Archived automatic vehicle location
(AVL) and automatic passenger count (APC)
data

have great potential for improving transit
management and performance. This report has
reviewed the history and state of the practice in
AVL
-
APC data collection and analysis. To
develop guidance for system design, existing
and potential analyses and tools

that use AVL
-
APC data to improve management and
performance are reviewed and their data needs
analyzed. Analysis tools for running time,
waiting time, and crowding were developed in
the course of this project.

AVL systems have traditionally been
designed
primarily for real
-
time applications.
For investigating specific incidents, archives of
almost any AVL data stream can be used in
playback mode. However, for analysis of
historical data combining multiple days of
observations, data requirements substantial
ly
exceed what will suffice for real
-
time
monitoring. The following are the main
conclusions regarding how AVL
-
APC systems
should be designed to provide a valuable data
archive:

o

Storing data on board frees the system
from the capacity restrictions of
trans
mitting data records over the air.

o

Time
-
at
-
location data (i.e., stop and
time
-
point records) are needed for
analyses that aggregate over multiple
days of observation, such as running
time and schedule adherence analysis.

o

Stop
-
level records permit running
time
analysis and schedule
-
making at greater
geographic detail than time
-
point
records, better serving passenger
information needs and supporting better
operational control.

o

Integrating on
-
board devices adds
information to the data stream that can
be valua
ble in its own right as well as
aid in matching captured data to the
base map and schedule. The most
valuable devices to integrate are door
sensors, odometer (transmission), and
radio control head.

o

Designers should pay attention to a data
collection and pr
ocessing system's
ability to accurately determine arrival
and departure times at stops, identify
holding, and deal with multiple
apparent stops and starts at bus stops
and in terminal areas. Having data from
both door sensors and odometers is
particularly
valuable in this respect.

o

Integrating AVL with the fare collection
system offers a potentially powerful
means of measuring ridership patterns,
because matching fare media serial
numbers offers a means of observing
linked trips.




34

Automatic data collection c
an
revolutionize schedule planning and operations
quality monitoring as agencies shift from
methods constrained by data scarcity to
methods that take advantage of data abundance.
The large sample sizes afforded by automatic
data collection allow analyses t
hat focus on
extreme values, which matter for schedule
planning (e.g., how much running time and
recovery time are needed, what headway is
needed to prevent overloads) and service
quality monitoring (e.g., how long must
passengers budget for waiting, how o
ften do
they experience overcrowding). Stop
-
level data
recording provides a basis for stop
-
level
scheduling, a practice with potential for
improved customer information and better
operational control. With AVL
-
APC data,
trends can be found that might other
wise be
hidden. Regularly analyzing AVL data gives a
transit agency a tool for taking greater control
of its running times by offering a means of
detecting causes of delay and evaluating the
effectiveness of countermeasures.

Two sets of analysis tools were

developed as part of this project. One uses
running time data to suggest periods of
homogeneous running times, analyze user
-
selected running time periods and scheduled
running times, and create stop or time
-
point
-
level schedules. It includes a valuable "w
hat
-
if"
tool that allows schedule planners to propose a
scheduled running time period and running
time, and immediately see how that running
time would have performed based on the
historical data. The tool offered for segment
-
level running times uses a sta
tistical approach
that, if combined with operational control in the
form of holding early trips, has great potential
to improve on
-
time performance.

New tools were also developed on a
spreadsheet platform to evaluate waiting time
and crowding from the cus
tomer's perspective
using AVL and APC data. Unlike traditional
methods, they focus on the extreme events
(e.g., very early and late buses, very long
headways, very crowded buses) that most affect
customer satisfaction. A whole new framework
was developed f
or evaluating passenger waiting
time, one that gives attention to the time that
passengers have to budget for waiting, not just
the time they actually spend waiting. Three
new measures of waiting time are proposed:
budgeted waiting time, potential waiting
time,
and equivalent waiting time, the latter being a
comprehensive summary of passengers' waiting
cost. This framework is superior to traditional
measures of waiting time because it accounts
for the impact of service unreliability on
passenger waiting tim
e.

The development of AVL
-
APC data
collection and analysis capability poses
numerous organization challenges. Perhaps the
greatest is raising awareness within the
organization of the value of archived AVL
-
APC data in order to ensure that AVL systems,
which

are often procured to serve real
-
time
applications, have a design and the database
support needed to achieve their potential for
archived data analysis.

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35

Benefits of Signal Timing Optimization and ITS to Corridor Operations

by Lloyd J. French. and
Milli
e S. French, French Engineering, LLC, 114 Cooley Estate Rd., Smithfield. PA 15478
(Pennsylvania Department of Transportation, Bureau of Planning and Research, Commonwealth
Keystone Building, 400 North Street. 6
th

Floor East, Harrisburg. PA 17120) (Aug 2006
)



Highlights



The purpose of this research was to develop
and use the SimTraffic microsimulation
model in the assessment of signal timing
alternatives on a congested corridor.



The research stresses the importance of
calibration and validation of SimTraf
fic
models, and presents a methodology for
doing so.


This study relied heavily on field
-
collected data supplemented by engineering
drawings supplied by PennDOT. The field
traffic data collection included turning
movement counts, truck counts, probe vehic
le
travel time runs, queue discharge
headways/saturation flow rates for critical
movements, cycle lengths and splits for critical
phases, and queue lengths/cycle failure
observations during congested periods. A
separate model was developed for each peak
pe
riod, however, the main difference between
the models were the traffic volumes
-
including
trucks
-
and the traffic signal timings. These data
were meticulously entered into the model, and
only slight modifications of the signal timings
were required to replic
ate the operational
problems and travel times observed in the field.

Additionally, the probe vehicle travel
times measured from the simulation were found
to be highly beneficial. However, they are labor
intensive since they are not a direct output of
simul
ation. As such, they were only compiled
for one of the 10 runs of each model. However,
they were compiled for the same run in all
cases.

Furthermore, the 10 runs of the model
are expected to be sufficient for networks with
little to moderate congestion. Ho
wever, for
models with heavy congestion and overcapacity
conditions, additional runs may prove to be
beneficial.

Finally, the simulation model was used
to assess four signal timing alternatives to
improve operations in the congested corridor of
S.R. 0021 b
etween Daniel Drive and Santa
Maria Drive/Uniontown Mall drive in South
Union Township, Pennsylvania. This corridor
has five signalized intersections in a space of
3,000 feet. In spite of the close spacing of the
signals, the findings of the engineering an
alysis
and simulation surprisingly indicated that the
benefits of progression provided by
coordination were far outweighed by the costs
incurred through the reduction of flexibility at
the critical two intersection system at the
Cherry Tree Lane and Matthe
w Drive
intersections when semi
-
actuated control with a
fixed cycle length was imposed, unless the
capacity
-
problems at the two
-
intersection
system were resolved. These findings were
reinforced by the field
-
collected travel time
information, which demonstr
ated that half the
travel time in the corridor was spent stopped at
this two
-
intersection system, and that the
likelihood at being stopped at another
signalized intersection in the corridor was
minimal. A phasing change that improved
operations at the crit
ical two
-
intersection


36

system was proposed. This was found to be
beneficial whether the corridor was coordinated
or not, however, implementing coordination in
the corridor in conjunction with the phasing
change yielded even greater benefits.

The most import
ant step to take in the
implementation of this research is to implement
one of the signal timing alternatives and field
-
measure the benefits. From an engineering
standpoint, two of the alternatives
demonstrated potential in the simulations to
alleviate con
gestion in the corridor. If these
benefits are realized, this can be a major
improvement for the motoring public in this
corridor. From a scientific point
-
of
-
view, there
have been very few projects in which a study
has been performed to verify that the
ant
icipated benefits predicted by SimTraffic
were realized when the signal timing
improvement was implemented. This would be
of great value to the scientific community. Note
that implementation of one of the signal timing
alternatives may require a traffic si
gnal design
plan and updated permit drawings. If the
phasing change is implemented, the
Department may want to consult the
Guidelines
for the Activation, Modification, or Removal of
Traffic Signal Control Systems
-

An ITE
Proposed Recommended Practice

by t
he
Institute of Transportation Engineers (ITE).

In the interim, the results of the Phase 1
research are of some benefit to the engineering
community since (1) the research stresses the
importance of calibration and validation of
SimTraffic models, and pres
ents a
methodology for doing so; (2) it introduces at
least one new performance measure for
evaluating corridor operations; and (3) it
provides some insight on Synchro optimization
and how it might be used to arrive at different
timing plans that achieve d
ifferent objectives.
Selected presentations at conferences such as
the Pennsylvania Traffic and Safety
Conference, coupled with the distribution of the
Phase 1 Final Report to the various PennDOT
District Traffic Units would raise sufficient
awareness.

If
the anticipated benefits of the
selected signal timing improvement alternative
are realized, a major implementation effort
should be made with the local municipalities in
Pennsylvania that may be struggling with
congested corridors. This would raise
awaren
ess of the potential benefits of the signal
timing changes, and encourage similar projects
statewide. However, it may be prudent to'
ensure that the selected case study corridor is
successful before citing it as a model. This can
only be done by implementi
ng a signal retiming
alternative and field
-
measuring the benefits.


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37

Components of Congestion

by Jaimyoung Kwon, Michael Mauch, and Pravin Varaiya

in
Transportation Research Record 1959

(Transportation Research Board, 500 Fifth Street, NW,
Washington, DC
20001; (202) 334
-
3213; http://gulliver.trb.org/bookstore) (2006)



Highlights



Incidents and special events together
account for 17.8% of total delay.



Lane closures caused no delay because
closures were not scheduled during peak
hours.



Rain caused 1.6% o
f total delay.



33% of all delay could be eliminated by
ideal ramp metering.



47% of delay is caused by excess demand.


Congestion is caused by incidents,
special events, lane closures, weather,
inefficient operations, and excess demand.
Knowledge of the
congestion pie is essential to
the selection of effective congestion mitigation
strategies. This paper presents a method for
dividing the total congestion D
total

into six
components:

1.

D
coi

is congestion caused by incidents,
which could be reduced by quicker

response;

2.

D
event

is congestion caused by special
events, which could be reduced by public
information and coordination with transit;

3.

D
lane

is congestion caused by lane closures,
which could be reduced by better
scheduling of lane closures;

4.

D
weather

is con
gestion caused by adverse
weather, which could be reduced by
demand management and a better weather
response system;

5.

D
pot

is congestion that can be eliminated by
ideal ramp metering; and

6.

D
excess

is residual delay, largely caused by
demand that exceeds the
maximum
sustainable flow.


The method is applied to a 45
-
mi
section of I
-
880 in the San Francisco Bay Area
with data for January through June, 2004.

The method refines previous studies
that group D
pot

and D
excess

together as recurrent
congestion. It also r
efines the authors' previous
work, which considers only three components
(D
coi
, D
pot
, and D
excess
). Transportation agencies
measure recurrent congestion in various ways
and find it accounts for 40% to 70% of total
congestion. The availability of more
compr
ehensive data has prompted attempts to
separately estimate the contribution of different
causes of congestion. Some studies divide total
congestion into recurrent and nonrecurrent
congestion, and some studies divide the
nonrecurrent congestion into acciden
t
-
induced
congestion and other incident
-
induced
congestion. There also are estimates of the
congestion caused by adverse weather. These
studies are reviewed in the next section.

The studies leave a large fraction
(between 40% and 70%) of the total congesti
on
unexplained. This unexplained residual is often
called recurrent congestion. One cause of these
delays may be unusual volume surges at ramps
that are not being effectively handled by the
ramp metering program. The proposed method
estimates this potentia
l reduction in delay, D
pot
.




38

Conclusion

Between 1980 and 1999, highway route
miles increased 1.5% whereas vehicle miles of
travel increased 76%. In 2000, the 75 largest
metropolitan areas experienced 3.6 billion
hours of delay, resulting in $67.5 billion i
n lost
productivity, according to the Texas
Transportation Institute. Mitigating congestion
through more efficient operations is a priority
of transportation agencies. The first step in
designing an effective mitigation strategy is to
know how much each ca
use contributes to
congestion. One can then design a set of action
plans, each aimed at reducing the contribution
of a particular cause. The more detailed the set
of causes that are considered, the more
effective the strategy that can be devised.

Incidents

and special events together
account for 17.8% of total delay. Lane closures
caused no delay because delay
-
causing closures
were not scheduled during peak hours. Rain
caused 1.6% of total delay. A surprisingly large
33% of all delay could be eliminated by
ideal
ramp metering. Finally, 47% of the delay is
caused by excess demand.

The 33% potential reduction due to
metering needs to be interpreted with caution,
as the maximum possible reduction. Even with
such precaution, if these estimates are
supported in
more detailed studies, it is likely
that most congestion mitigation strategies
would harvest large potential gains from ramp
metering.

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39

Congestion Pricing: A Primer,
by Patrick Decorla
-
Souza (Federal Highway Administration, Office
of Transportation Manage
ment, HOTM, 400 Seventh St. SW, Room 3404, Washington, DC 20590;
http://www.ops.fhwa.dot.gov/publications/congestionpricing/congestionpricing.pdf; phone: (202)
366
-
4076; E
-
mail:
Patrick.Decorla
-
Souza@dot
.gov
) (Dec 2006)



Highlights



Congestion pricing benefits drivers and
businesses by reducing delays, increasing
the predictability of trip times, and allowing
for more deliveries per hour.



Congestion pricing benefits mass transit by
improving transit sp
eeds and the reliability
of transit service.


Congestion pricing benefits drivers and
businesses by reducing delays and stress, by
increasing the predictability of trip times, and
by allowing for more deliveries per hour. It
benefits mass transit by impro
ving transit
speeds and the reliability of transit service,
increasing transit ridership, and lowering costs
for transit providers. It benefits State and local
governments by improving the quality of
transportation services without tax increases or
large c
apital expenditures, by providing
additional revenues for funding transportation,
by retaining businesses and expanding the tax
base, and by shortening incident response times
for emergency personnel and thus saving lives.
By preventing the loss of vehicle

throughput
that results from a breakdown of traffic flow,
pricing maximizes return on the public's
investment in highway facilities. And it
benefits society as a whole by reducing fuel
consumption and vehicle emissions, by
allowing more efficient land use

decisions, by
reducing housing market distortions, and by
expanding opportunities for civic participation.


Benefits to Transit Riders and Carpoolers

Pricing in combination with transit
services provides bus riders with travel time
savings equivalent to t
hose for drivers, and
reduces waiting time for express bus riders due
to more frequent service. Introduction of
pricing in central London and Stockholm has
resulted in significant shifts of commuters to
transit, particularly buses. Bus delays in central
Lo
ndon dropped by 50% after the pricing
scheme was introduced. There was a 7%
increase in bus riders. In Stockholm, 200 new
buses were put into service in August 2005,
several months in advance of the pricing trial,
which began in January 2006. After the pri
cing
scheme was implemented, daily public
transportation use compared to the same month
in 2005 was up by 40,000 riders daily.
Ridership on inner
-
city bus routes rose 9%
compared with a year earlier.

Within three months of the opening of
the priced express

lanes on California's SR
-
91,
a 40% jump occurred in the number of vehicles
with more than three passengers. Ridership on
buses and a nearby rail line have remained
steady. On San Diego's I
-
15 HOT lanes,
revenues generated by toll
-
payers financed
transit i
mprovements that contributed to a 25%
increase in bus ridership.

After the HOV lanes were converted
into HOT lanes on I
-
15 in San Diego,
carpooling increased significantly, even though
there was no change in incentives to carpool
--

carpoolers continued to

use the lanes free of
charge, as they did before the lanes were


40

converted. Similar effects were observed when
the HOV lanes on I
-
25 in Denver were
converted to HOT lanes in June 2006.


Benefits to Drivers

On the State Route 91 priced lanes in
Orange Coun
ty, California, traffic during rush
hours moves at over 60 mph, while the traffic
in adjacent lanes crawls at average speeds of 15
mph or less. Commuters on the priced express
lanes thus save as much as half an hour each
way on the 10
-
mile trip, or as much

as an hour
a day.

If we could use pricing to restore free
-
flowing traffic conditions on other metropolitan
freeways during rush hours, similar results
could be achieved. An average commuter using
a 5
-
mile freeway segment twice each day (i.e.,
once in each

direction) would save about half
an hour each day, or 120 hours annually
--

equal to three weeks of work or leisure time.

The day
-
to
-
day variation in travel times
is now understood as a separate component of
the public's and business sector's frustration
with congestion. An important benefit of
pricing is that it guarantees toll
-
paying vehicles
a reliable trip speed and travel time.



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41

Do E
mployee Commuter Benefits Reduce Vehicle Emissions and Fuel Consumption?

by Erik
Herzog, Stacey Bricka, Lucie Audette, and Jeffra Rockwell

in Transportation Research Record
1956

(Transportation Research Board, 500 Fifth Street, NW, Washington, DC 20001; (2
02) 334
-
3213; http://gulliver.trb.org/bookstore) (2006)



Highlights



Comprehensive benefits packages with
financial incentives, services produce
reductions in VMT of about 15%.



Benefits packages that offer only services
and information appear to produce
reductions of about 7%.


Best Workplaces for Commuters
(BWC) is a voluntary government
-
industry
partnership sponsored by the U.S.
Environmental Protection Agency (EPA) and
the U.S. Department of Transportation that
began in May 2001. Its goal is to reduce

vehicle emissions and traffic congestion by
encouragement of employers to offer a
comprehensive package of employee commuter
benefits (subsidized transit or vanpool passes,
liberal telework policies, supporting measures
for carpooling or bicycling, etc.)
as part of their
employee benefits packages.

The BWC survey was conducted in the
fall of 2004. The purpose of the survey was to
determine the difference between the
commuting patterns of employees who receive
BWC commuter benefits and those who do not
and
to estimate the resulting savings in trips,
vehicle miles traveled (VMT), and emissions
and fuel consumption. Employers recognized
as BWCs in the Denver, Colorado; Houston,
Texas; San Francisco, California; and
Washington, D.C., metropolitan areas were
ran
domly sampled and recruited into the survey
with a combination of telephone and e
-
mail
communications. One indicator of the
variability of commuting conditions in the four
areas selected are the census data on drive
-
alone rates for workers in the zip codes

in
which BWC employers are located: 74% for
Denver, 75.2% for Houston, 68.4% for San
Francisco, and 55.4% for Washington, D.C. As
of September 30,2004, 617,391 of 2,024,906
commuters employed at BWC work sites
nationwide (approximately 30% of the total)
w
ere in these four urban areas.

The survey was administered via the
Internet at BWC work sites to two groups of
respondents: those who were eligible for BWC
level commuter benefits (referred to in this
report as the BWC group) and those who were
not eligibl
e for the benefits because they were
contractors, temporary employees, or others
ineligible for company benefits (referred to as
the reference group). Of the 6,708 employees,
6,075 were in the BWC group and 633 were in
the reference group.

The reference gr
oup was initially
established as a control group that represented
employees who were in the same transportation
environment as the employees of the BWCs,
but who were ineligible for BWC benefits and,
therefore, whose travel choices are unaffected
by BWC be
nefits. As it turned out, the
respondents in the reference group were
exposed to the same services, marketing
programs, and corporate focus on the use of
alternative modes of transportation. Most
(55%) indicated that they received information
on ways to ge
t to work other than riding alone,
and many (37.6%) indicated that they were able


42

to take advantage of some of the employer
-
provided services, such as carpool matching
and bicycle facilities. As a result, their
responses are used as a measure of the
increm
ental change associated with the
provision of BWC
-
level commuter benefits at a
work sire where a lesser package of commuter
benefits is offered.

The results for both the BWC and the
reference groups are presented throughout this
analysis and are compared w
ith the commuting
patterns of the at
-
large population working in
the same zip codes as that working at the BWC
work sites participating in this survey. To do
this, virtual groups of the same sizes and with
the same average trip distances as the BWC
and the

reference groups were created, but their
mode distributions are those obtained from the
2000 census for people working in the same zip
codes as those working at the work sites
surveyed. Census mode shares, such as trip
distance and carpool occupancy, were

mapped
onto data from the survey respondents to obtain
an estimate of what the travel activity for the
BWC and the reference groups would have
been had they traveled to work by the same
modes as all others working in the same zip
codes.

These groups (ref
erred to as census
groups) serve as control groups and provide an
independent estimate of work
-
related travel
without the BWC marketing to which the
reference group has been exposed. In sum, the
three groups can be defined as follows:

1)

BWC group
, which incl
udes employees
eligible for comprehensive commuter
benefits and general marketing
information meeting the BWC National
Standard of Excellence from employers
participating in the BWC program;


2)

Reference group
, which includes
employees who are not eligible f
or
BWC benefits but who have specifically
been exposed to BWC marketing
messages and, in some cases, who have
access to BWC support benefits; and

3)

Census groups
, which are characterized
by the average mode share distribution
for all employees in the zip cod
es
surveyed, regardless of the commuter
benefits and the marketing messages
that they receive. These general data
were used to provide a natural
distribution of survey responses for both
the BWC and the reference groups.
Because it is based on census data,

the
census group includes individuals who
receive some level of commuter
benefits; hence, it is not a pure nondoer
group.


Conclusion

The results of this survey indicate that
when employers provide employees with
incentives to commute by means other than

driving alone, significant percentages of them
take advantage of these benefits.
Comprehensive benefits packages such as those
enjoyed by commuters in the BWC group, with
financial incentives, services (such as a
guaranteed ride home and carpool matching)
,
and informational campaigns, appear to
produce reductions in the numbers of trips and
VMT and the amounts of pollutants and fuel
consumption of about 15% even by the use of
conservative assumptions. Benefits packages
that offer only services and informat
ion appear
to produce reductions of about 7% by the use of
conservative assumptions.



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43

How Traffic Jams Are Made In City Hall
in
Reason
by Sam Staley and Ted Balaker (Reason
Foundation, 3415 S. Sepulveda Blvd., Suite 400, Los Angeles, CA 90034; (310) 3
67
-
6109;
http://reason.com/news/show/119192.html) (April 2007)



Five Ways o Reduce Traffic Congestion



Expand capacity
.



Better management of the existing road
network.



Market pricing for roads.



Market pricing for parking.



Privatization.


According to the

U.S. Census Bureau,
the typical driver in America's metropolitan
areas takes 21 minutes to get from home to
work. If you take public transit, the average
commute stretches to 36 minutes.

The U.S. Department of Transportation
puts the yearly cost of conge
stion at $168
billion. But the planning gurus who are
supposed to solve our transportation problems
are in the grip of transitphilia and autophobia;
their beliefs about how cities and transportation
work are grounded more in nostalgia than in a
realistic v
iew of the world we live in now. The
public policies they try to enforce make it
harder to get to work, pick up kids from school,
or go shopping. They are deliberately fostering
congestion.


Five Ways o Reduce Traffic Congestion

Creative construction
. Exp
anding
capacity doesn't always mean adding lanes to
congested roads, although that's often a good
idea as well. In densely populated Southern
California, portions of the highway network are
elevated well above the ground, including the
Harbor Transitway ap
proaching downtown Los
Angeles. In Texas, San Antonio and Austin
have double
-
decker freeways as well. In 2006
Tampa opened its cross
-
town expressway, an
elevated road built in the median of an existing
four
-
lane highway.

If going up is a problem, you can a
lso
go down. Australia has done an effective job of
using tunnels to connect highways while
preserving neighborhoods, an excellent
alternative to destroying businesses and homes.

Smarter management
. Building new
capacity can get you only so far. The Federa
l
Highway Administration estimates that half of
all congestion could be eliminated simply
through better management of the existing road
network. Among other approaches, this could
mean metering freeway ramps, turning two
-
way streets into one
-
way streets,
and improving
traffic light coordination. According to the
Institute of Transportation Engineers, better
-
coordinated lights can reduce stops by as much
as 40%, thereby cutting gas consumption,
emissions, and travel times.

Market pricing for roads
. One
espe
cially fruitful idea is high
-
occupancy toll
(HOT) lanes, which allow drivers who put the
highest priority on quick commutes to pay a
premium for uncongested lanes. These have
been built in Denver, Houston, and
-
yes
-
Minneapolis, among other cities. In Atlant
a
several private companies have submitted plans
to build new HOT lanes on their own dime.
During rush hour, the congestion difference
between the special lanes and the regular lanes
can be the difference between going 15 miles
per hour and doing 65.

Areas

with lots of car pool lanes could
convert those to HOT lanes, add some


44

connectors, and create a congestion
-
free HOT
network. Transit boosters, take note: It would
be easy to tweak the arrangement to guarantee
bus riders a speedy trip too.

Market pricing f
or parking
. On 99% of
our trips we park for free, thanks largely to the
minimum parking requirements embedded in
our zoning codes. Eliminating those
requirements would allow market forces to
reflect the true cost of parking. Instead of
adhering to arbitrar
y regulations that often
order more spaces than necessary, developers
would have greater flexibility to build only the
number of spaces that is needed. Workplaces
would be more likely to adopt parking cash
-
out
programs, which give employees who do not
driv
e to work a share of the money that
otherwise would have gone toward parking
costs. Employees would be more likely to work
from home.

Market pricing for parking would
reduce traffic too. If drivers had to pay the full
cost of parking, they might be less in
clined to
take certain trips, thus putting a dent in
congestion. More important, when parking is
scarce but free (or underpriced), drivers have
an incentive to keep the spots as long as
possible. When it is scarce but costs money,
drivers are less likely t
o dally. One additional
result: Other drivers have less need to circle
around and around, hoping eventually to spot
an empty space.

Traditional parking meters can be
notoriously inconvenient, but they aren't the
only way to pay for parking. Aspen, Colorado
,
uses a variety of new technologies, including
personal in
-
vehicle meters. The town
determines its parking rates by zones; prices are
highest in the city center and drop the further
you are from the core. Motorists simply park,
type in the number of their

parking zone, turn
on the meter, and hang it from the rearview
meter. A timer deducts the prepaid amount
until the driver returns. No one has to hunt for
loose change.

Privatization
. We're much more likely
to adopt ideas like the above when roads are
buil
t and managed by companies responding to
market incentives, not by government officials
responding to planning fads and political clout.
Private companies can create and operate
highways using toll revenues as a funding
source. The government can also conv
ert
existing roads to privately managed systems to
allow improvements and expansions of the
existing network.

For a spectacularly successful example,
consider the 407 Electronic Tollway outside
Toronto. This innovative road isn't fully
private, but it was
built by a private company
(the Canadian Highways International
Corporation) and is now managed by another
private company (407 International) that
bought a 99
-
year lease from the government of
Ontario. Yet another company, Hughes
Electronics, equipped it
with an electronic toll
-
collecting system that eliminates toll booths
and the congestion they can cause.


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45

Identification of Core Functions and Development of a Deployment Planning Tool for Safety
Service Patrols in Virginia

by Praveen K. Edara and Lance
E. Dougald, Virginia Transportation
Research Council, 530 Edgemont Road, Charlottesville, VA 22903 (Virginia Department of
Transportation, 1401 E. Broad Street, Richmond, VA 23219) (Dec 2006)



Highlights



The core functions of Safety Service Patrols
are i
mproved safety for motorists in distress,
improved transportation system security, &
creation of goodwill for the state agency.



Incidents can be statistically predicted with
the knowledge of freeway segment's AADT,
length, average daily percent of ADT
serv
ed, and the truck percentage.



In urban regions, the operating cost of SSPs
are typically outweighed by the benefits the
service provides to the traveling public.


A core set of functions can be identified
that are applicable to all Safety Service Patrol
(
SSP). These functions are consistent with
those of other programs throughout the nation
and address the elements of incident
management (IM): detection/verification and
response, scene management, traffic
management, incident clearance, and motorist
inform
ation.

The direct benefits that coincide with
the majority of the core functions of the
Virginia Department of Transportation’s
(VDOT's) SSP programs are improved safety
for motorists in distress, improved
transportation system security, and creation of
go
odwill for the state agency. The core
functions of VDOT's SSP programs that
provide the greatest number of direct benefits
are (1) provide traffic control/manage lane
closures as part of the traffic management goal
of IM and (2) push vehicle from travel la
ne as
part of the incident clearance goal of IM.

A limited number of SSP programs
throughout the United States have developed
criteria or planning tools for deployment. Those
that have such tools typically use qualitative
and quantitative techniques to der
ive them. The
data that drive such criteria include traffic and
geometric characteristics as well as incident
and/or crash statistics.

The planning tool developed in this
study can assist VDOT decision
-
makers when
considering expanding SSP coverage and/or
altering existing route coverage. The developed
tool is a segment
-
based ranking scheme and
can be applied to all rural and urban freeway
segments in Virginia. An important criterion
that drives the ranking scheme is the predicted
number of incidents for a
segment under
consideration. An incident prediction model
was developed that can be used in all locations
in Virginia to predict the number of incidents
on a given segment. Based on the model's
goodness
-
of
-
fit measures, it was found that
incidents can be s
tatistically predicted with the
knowledge of freeway segment's AADT,
length, average daily percent of ADT served,
and the truck percentage. This model can
produce reasonable estimates of incidents as
long as the input variables for the segment lie
within t
he range of the values used in the model
development process.


Recommendations

VDOT's SSP decision
-
makers should
prioritize the core functions of their programs
in relation to the direct, indirect, and incidental


46

benefits each provides. Emphasis should be
placed on those core functions that provide the
most direct benefits. Indirect and incidental
benefits are also of importance and should not
be overlooked in the prioritization process.

To maintain statewide consistency with
SSP core functions, each region
al SSP manager
should communicate and keep abreast of
changes in core function priorities in other
operations regions.

The SSP deployment planning tool
should be used by VDOT's regional
-
operations
directors as they consider the deployment of
new patrols or

altering existing ones. To do
this, all existing and potential patrol routes
should be inc1uded in the evaluation. Each
route must be divided into its constituent
segments (traffic links), and each segment
scored using the predicted number of incidents,
L
OS, planned projects, air quality, maximum
access distance, maximum structure length,
AADT, and daily truck volume. For each patrol
route, the segment scores should be summed to
obtain individual route scores. All routes
should then be ranked based on thei
r scores.
When ranking the routes, only routes within a
regional boundary should be compared because
of inherent differences in regional incident
histories, traffic characteristics, and freeway
geometries. For example, all routes considered
in the Hampton
Roads region should be
compared with each other, not with routes in
the NOV A or Salem regions.

As a means of improving the SSP
deployment planning tool, VDOT regional
operations directors should consider additional
research that expands upon the current d
ataset.
This can be accomplished by incorporating
incident data over multiple years from
established (existing) deployments and newly
established deployments. To be consistent with
the data requirements of the deployment
planning tool, all SSPs should main
tain
adequate recordkeeping procedures. At a
minimum, drivers should record the dates and
locations of all assisted incidents. For other
evaluations (e.g., benefit
-
to
-
cost and
performance measure evaluations), additional
data such as incident duration, typ
e, and lateral
location should be recorded.


Costs and Benefits Assessment

The SSP deployment planning tool will
provide a clear indication of which routes
would benefit the most from the deployment of
SSP and thereby will allow for better informed
investm
ent decisions. The costs involved in
using this tool, in terms of person
-
hours, are
minimal when compared to the benefits of
prudent funding allocations.

In urban regions, the operating cost of
SSPs are typically outweighed by the benefits
the service prov
ides to the traveling public
(e.g., savings in delay and associated savings in
fuel consumption and emissions). In rural
areas, quantifying the benefits of SSP programs
can be complex because of the difficulty in
putting a dollar figure on customer satisfa
ction.
This can be addressed with customer
satisfaction survey cards, which are given to
motorists requesting an estimate of the value
associated with the services rendered. By
compiling these surveys, an overall estimate of
customer satisfaction can be qu
antified.



TRANSPORTATION RESEARCH DIGEST

ARIZONA TRANSPORTATION INSTITUTE

e
-
mail
jsemmens@cox.net



MA
Y 2007



47

Rush Hour: How States Can Reduce Congestion Through Performance
-
Based Transportation
Programs
by

Wendell Cox, Alan E. Pisarski and Ronald D. Utt (Heritage Foundation, 214
Massachusetts Ave NE, Washington DC 20002
-
4999; ph 202.546.4400;
http:
//www.heritage.org/Research/SmartGrowth/bg1995.cfm) (January 10, 2007)



Highlights



Performance measures should guide
investment decisions.



Most states do not effectively use
performance measures to guide decision
making.



Road investments are more cost
-
ef
fective
than transit investments.



A revised planning process is recommended.


Traffic congestion in most of America's
metropolitan areas has worsened steadily over
the past two and a half decades and is at its
worst in the nation's major commercial center
s.
A key reason for this worsening congestion is
that road capacity has not kept pace with
population, licensed drivers, automobiles, or
vehicle miles traveled (VMT). Since 1970, the
number of licensed drivers had risen by 71%,
the number of registered veh
icles had risen by
99%, and miles driven had risen by 148%, and
yet new road miles had increased by just 6%.

Some state transportation officials are
adopting new strategies to use available
resources more efficiently in order to provide
the greatest measu
re of transportation services.
These plans differ significantly in detail, but all
of them rely on quantitative performance
measures that the state DOT is required to
attain over a specified period of time.

Essential to the creation and operation
of a syst
em based on quantitative performance
goals is the availability of timely and accurate
information covering all facets of a state's
transportation system. This includes measures
of regional congestion, road conditions, and
safety measures as well as extensi
ve details on
operational and capital costs by mode,
geography, and project needed to conduct the
cost
-
benefit analyses critical to any
perfor-mance
-
based program.

Because few states collect and compile
the type of data necessary to operate a
performance
-
b
ased accountability system
effectively, one of the earliest steps in
implementing such a system is to establish a
comprehensive data collection and reporting
system. The availability and dissemination of
detailed data on all facets of a state's
transportat
ion network are also essential to
gaining, justifying, and holding support for the
program among the public, the media, and
other state officials.

Most transportation programs are ill
-
equipped to serve their users because they lack
basic information on how

much it costs to
provide a particular transportation service by
mode and by location. Few, if any, state DOTs
have attempted such analyses, and the federal
government has done it only once. Absent
information on unit costs by mode of
transportation, offic
ials cannot allocate scarce
resources effectively among alternative modes
to maximize consumer mobility.

The table below reports the results of a
federal study of the cost of the federal subsidies
received to passengers of different modes of
transportation
. Passenger subsidies for transit
are large. Automobiles, on the other hand, yield
a profit to the government because the user fees


48

motorists pay into the highway trust fund
exceed spending on roads.


Net Federal Subsidies Per Person
-
Mile

Mode

Subsidy

Au
tomobiles*

(0.2 cent)

Intercity Buses

0.5 cent

Transit

16 cents

Amtrak

21 cents

Source: USDOT, 2004

*Autos actually pay more into the trust fund than is spent
to build roads for them.


With the cost differentials described
above, a performance
-
based s
ystem would
suggest that states and the federal government
shift public financial resources, civic energy,
and government attention from transit to road
building so as to maximize the impact of
available financial resources on improving
mobility.

Based on

the preceding analysis, a state
transportation program built on quantitative
measures of performance and accountability
should include five components:

State Traffic Flow Improvement Plan
.
This plan will include immediate, low
-
cost,
high
-
return investment
s throughout the state
that reduce congestion and other impediments
to traffic flow that affect safety and the
environment. Such actions will include traffic
management improvements, vehicle incident
response systems, ramp metering, and other
information t
echnologies that enhance the flow
of the state's existing investment in its
transportation system.

State Traffic Congestion Reduction
Program
. This plan will include longer
-
term
capital investments as part of a performance
-
based investment plan to reduce c
ongestion
throughout the state. Investments will be
ranked by their ability to reduce delay.
Performance of the system and progress toward
the goal will be strictly monitored. The goal of
this program is to increase the entire state's
competitiveness in bo
th the national and
international spheres.

State Infrastructure Improvement Plan
.
This plan will include actions to bring the
condition of the state's inadequate bridges,
roadways, and transit facilities up to acceptable
levels. Those levels will be strict
ly monitored
and rated against predefined quantitative
performance standards of quality.

State Traffic Safety Enhancement Plan
.
This plan will include the provision of safer
and more secure transportation services on the
state's roadways and rails and will

be a key
com-ponent of the DOT's measure of
performance and accountability. This plan will
establish goals for improving safety as
measured by the annual rate per 100 million
VMT of collisions, personal injuries, and
fatalities in the state.

State Data Co
llection and Reporting
Plan
. This plan requires the state to establish a
comprehensive and timely data collection and
reporting system that covers operating and
capital costs by mode and by normalized
standards such as per
-
person
-
mile measures;
truck volum
e and truck share of VMT; quality
of service measures in terms of congestion and
safety; quantitative measures of the quality of
infrastructure, including roadbeds and bridges;
daily usage by mode by number of passengers;
and any and all other data necessa
ry to fulfill
the performance goals established in the plans.
The data will also be used to provide
meaningful periodic reports to the governor,
legislature, and public on all measures of
performance and progress, or lack thereof,
toward the goals establis
hed in the legislation.