<Back to ITS in Work Zones
Intelligent Transportation
Systems
in Work Zones
A Case Study
Work Zone Travel Time System
Reducing Congestion with the Use of a
Traffic Management Contract
Incentive During
the Reconstruction of Arizona State Route 68
October 2004
FHWA-HOP-04-032
EDL# 14001
FHWA
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Foreword
Dear Reader,
We have scanned the country and brought together the collective
wisdom and expertise of transportation experts implementing
Intelligent Transportation Systems (ITS) projects across the United States. This information will prove helpful as you set out to plan, design, and deploy ITS in your communities.
This document is one in a series of products designed to help you
provide ITS solutions that meet your local and regional transportation
needs. The series contains a variety of formats to communicate with
people at various levels within your organization and among your
community stakeholders:
- Benefits Brochures let experienced community leaders explain
in their own words how specific ITS technologies have benefited
their areas.
- Cross-Cutting Studies examine various ITS approaches that can be taken to meet your community's goals.
- Case Studies provide in-depth coverage of specific approaches
taken in real-life communities across the United States.
- Implementation Guides serve as "how to" manuals to assist your
project staff in the technical details of implementing ITS.
ITS has matured to the point that you are not alone as you move
toward deployment. We have gained experience and are committed
to providing our state and local partners with the knowledge they
need to lead their communities into the future.
The inside back cover contains details on the documents in this series,
as well as sources to obtain additional information. We hope you find
these documents useful tools for making important transportation
infrastructure decisions.
Sincerely,
Jeffrey F. Paniati
Associate Administrator for Operations
Acting Program Manager, ITS Joint Program Office
Federal Highway Administration
Preface
This case study is one in a series of documents that examines the use of
Intelligent Transportation Systems (ITS) in work zones. More information
on applications of ITS in work zones is available in the companion
document, Intelligent Transportation Systems in Work Zones -
A Cross–Cutting Study (Report No. FHWA-OP-02-025, EDL# 13600).
This case study presents information gathered through interviews with
key personnel on the Arizona State Route (SR) 68 project in Kingman,
Arizona, as well as information and photographs obtained during a site
visit. The authors greatly appreciate the cooperation of the Arizona
Department of Transportation and its partners, who made the production
of this document possible.
Contents
Project and System Background
The Arizona Department of Transportation (ADOT) used ITS to support
work zone operations during the reconstruction and widening of
State Route 68 (SR 68) in northern Arizona. The $42 million project
involved widening approximately 13.5 miles of an existing two-lane rural
highway into a four-lane divided highway. ADOT began the project in
the summer of 2000 and completed it in April 2002. The project was
unique in that ADOT procured it as a design-build project, the first rural
project of its kind in Arizona. Faced with many challenging features
on this project, ADOT determined that implementing ITS in the work
zone would be beneficial to keep traffic moving on one of the region's
most critical highways. ADOT decided to include an incentive/disincentive
provision in the project contract to encourage the contractor to minimize
work zone delays. ADOT needed a way to measure performance related
to the provision and turned to ITS to help.
SR 68 is a critical highway for the northwestern region of the state,
primarily serving commuter traffic traveling between Kingman, Arizona,
and the nearby cities of Laughlin, Nevada, and Bullhead City, Arizona
(shown in Figure 1). Several characteristics of SR 68 presented ADOT
with a challenge in completing the construction while promoting
mobility and safety. SR 68 is a major commuter route for those employed
by casinos and other entertainment venues in Laughlin. Due to the
nature of the employment in Laughlin, SR 68 does not have typical a.m.
and p.m. peak traffic periods, and generally has a steady volume of
traffic from early morning to late evening.
Figure 1 – Map of Project Location
Another characteristic of SR 68 is that the reconstructed section, which serves a significant amount of recreational vehicle and truck traffic, has a steep continuous grade of 6 percent. Due to the steep grade and significant amount of heavy vehicles using the route, ADOT determined
that truck escape ramps would be needed. The project also included
other challenging features, such as two structures to accommodate Big
Horn sheep crossings, a retaining wall, new drainage structures, and
approximately 2.5 million cubic yards of excavation.
The percentage of truck traffic on SR 68 increased after the 9/11/01 terrorist attacks,
when ADOT closed the route over the Hoover Dam to trucks. The route had previously served as
the main truck route between Arizona and Las Vegas. As a result, SR 68 has served as the primary
alternate for these detoured trucks since then, which has led to a 25 percent increase in truck
traffic.
In order to maintain traffic flow along SR 68 throughout the duration of the project, ADOT decided to include an incentive/disincentive provision in the contract. This provision, termed a "Traffic Management Incentive Specification," established a $400,000 bonus fund to encourage the design-build contractor to maintain a target travel time through the work zone. The provision required that the contractor select and pay for a system capable of collecting raw vehicle position data; calculate
average travel times through the work zone; and report these average
travel times to ADOT in 30-minute periods. The provision also stated
that the average travel time could not exceed 27 minutes, and that the
contractor would be charged a fee at a rate of $21.50 for each minute
of delay when the average travel time exceeded 27 minutes. The
requirement applied to both directions of travel, and the travel times
and penalties were assessed separately for each direction. According to
the clause, the contractor was to receive any bonus funds remaining at
the conclusion of the project. Additionally, in the event that the bonus
funds were depleted during the course of the project, the contractor
would be responsible for any additional fees incurred for continuing to
exceed the 27-minute target travel time. ADOT project managers
analyzed the data submitted by the contractor to identify any violations
and determine any resulting fees incurred.
ADOT arrived at the 27-minute figure by considering several factors.
Prior to construction, the average time to travel the project limits at the posted 55 mph speed limit was 17 minutes. ADOT determined this
baseline travel time by averaging actual travel time runs conducted at
various times of the day on various days of the week. ADOT expected
that the travel time during construction would increase to 21 minutes
due to lower posted speed limits (35 to 45 mph) and other traffic
control measures that would be in place. ADOT also anticipated that
heavy trucks traveling up the steep grade would continue to impact
traffic flow since there would be only one travel lane for each direction
of traffic during construction, as shown in Figure 2.
Figure 2 – Construction Along the Steep Grade on State Route 68
ADOT specified requirements for the use of a system to measure travel
time through the work zone based in large part on technology
demonstrations that key staff had viewed at the Rural Advanced
Technology and Transportation Systems annual conference in Flagstaff,
Arizona, in August 1999. ADOT had successfully used other
incentive/disincentive programs in the past, such as lane rental and a
quality workmanship incentive, and was interested in using similar
techniques on this project. ADOT was concerned, however, that the
contractor might plan for short frequent lane closures, thereby avoiding
penalty under the lane rental incentive (which issued penalties for lane
closures greater than five minutes in duration), but still imposing
unnecessary delay on motorists. To address this concern, ADOT decided
to supplement their planned incentive/disincentive programs with a
travel time incentive strategy to encourage the contractor to keep
traffic moving efficiently through the SR 68 work zone. The contractor
selected a camera-based license plate matching system by Computer
Recognition Systems to determine travel times through the work zone.
The system included two monitoring stations, one at each end of the
work zone, and a central processor. Cameras at the monitoring stations
took pictures of vehicle license plates entering and leaving the work
zone and the system used these images to determine vehicle travel
times through the work zone.
The SR 68 project is not the first use of a travel time ITS license
plate recognition system in a work zone in the United States. The state
of Massachusetts currently deploys a similar type of technology at its
Coolidge Bridge reconstruction project on Route 9 between Hadley and Northampton.
The Massachusetts system is primarily focused on traffic management, rather
than tracking contract incentives, and is expected to be in place until
2009. The system website (http://www.umass.edu/coolidgeinfo/)
provides real-time travel times, speeds, and camera images.
Back to Top
System Design, Selection, and Implementation
This section provides information on ADOT's experience in bringing the
system from the concept stage to fully operational.
In-House or Contractor Design
- ADOT staff developed performance-based specifications for a
travel time system so that the contractor would be free to choose a
system suitable for the project. The system needed to be capable of
measuring vehicle travel time within the project limits and providing
data the contractor would need to report average travel times for
30-minute periods.
System Selection and Procurement
- Other technologies for measuring travel time were considered
during the bidding process, including cellular phone tracking, vehicle
probes, and radar systems. However, the selected contractor chose
to use a license plate matching system.
- The main factors the contractor considered when selecting the
system included overall cost, speed of installation, and reliability.
In addition, the contractor found it important to choose a system
that had been demonstrated and proven successful.
Lease Versus Purchase
- ADOT elected not to purchase the system because it was a temporary
application specific to the SR 68 work zone. Therefore, ADOT
required that the contractor obtain the system and maintain it.
- The contractor purchased the equipment for the system. After
the project, the contractor sold the equipment back to the system
vendor, as they did not see the potential for using the equipment
again in the near future.
Testing
- The system vendor traveled to the project location to help the
contractor install the system and to ensure that it was working
properly prior to construction. The contractor also worked with the
system vendor to determine the proper placement of the cameras
within the work zone.
- Although measuring travel times in work zones with the use of
license plate matching is a fairly new concept, license plate matching
technology is well developed; therefore, the system required
minimal testing.
Training
- The system was simple to use and required minimal training for the
contractor's engineers, especially considering that the automated
system functions minimized the need to interact with the system on
a daily basis. The system vendor trained the engineers on how to
operate the system and gather the data from the automated system.
ADOT and the contractor found this training to be sufficient.
Back to Top
System Description and Operations
System Description
- The system consisted of two monitoring stations and a central
processor. Each monitoring station included an inductive loop
embedded in the roadway, a control cabinet with a communications
system, and two digital cameras (one for each direction of traffic)
linked to the cabinet via fiber-optic cable. In addition, each camera
was equipped with a light source to assist in reading license plates
with plastic covers.
- The system required access to public utilities for a power source
since power requirements for the lighting system made the use of
solar power prohibitively expensive. Figure 3 shows a light and
camera at one of the monitoring stations.
Figure 3 – Light and Camera Used to Collect License Plate Data
- The system used point-to-point microwave communication
technology that was already available at the project location.
This communication system provided substantial data throughput
(as much as 800 MB per second). The only drawback that ADOT
noted in terms of using this method of communication was that
line-of-sight was needed, which required the installation of repeaters
to relay signals from the roadside sites to the main transmitter.
- The central processor consisted of an industrial computer with a
processing speed of approximately 1 GHz, although the system could
have been operated using a computer with a processing speed
of 500 MHz. The operating system used was a standard commercial
off-the-shelf product.
- The system used a common RS-232 interface, which allows access
to system data via a wide range of communications and data
storage devices.
System Operations
- The system captured, immediately encrypted, and then stored
images of license plate numbers as vehicles entered and left the
work zone. Vehicles passing over the inductive loops triggered
the digital imaging process.
- The monitoring stations captured digital images of the vehicles'
rear tag numbers and stored them locally. The system would then
send the encrypted images to the central processing station every
10 minutes via point-to-point microwave technology.
- The central processor compared the encrypted images to match
vehicles entering the work zone with vehicles leaving the work zone.
The processor then compared the time a vehicle tag was detected
entering the work zone with the time it was detected leaving
the work zone to determine total travel time. The central processor
stored the travel time information and periodically sent it to the
contractor. The contractor then submitted an electronic copy of the
data in 30-minute averages to ADOT project managers on the first
day of each month.
- ADOT staff reviewed the data to identify any violations of the
travel time provision. If the average travel time for any 30-minute
interval was greater than 27 minutes, ADOT assessed the contractor
a disincentive fee. ADOT computed the total disincentive fee by
determining the delay, or the difference between the actual travel
time averages and the goal of 27 minutes for each 30-minute
interval. ADOT then charged the contractor a fee of $21.50 for
each minute of delay incurred per travel lane.
- The concept of the operations diagram for the system is shown in
Figure 4.
Figure 4 – Arizona ITS Concept of Operations
Contractor or Agency Staff
- The contractor monitored the system to assess whether its work
operations were creating excess delays. If travel times from the
system indicated delays, the contractor could adjust work operations
to try to reduce congestion.
- ADOT personnel also monitored the system periodically, as well as
reviewed the data submitted by the contractor to identify violations
of the travel time provision and used the data to calculate the
disincentive for any violations.
- The contractor was responsible for providing system maintenance
support. Using an automated system eliminated the need for
dedicated operations staff.
Coordination with Key Personnel, Other Agencies, and the Public
- The travel-time system required ADOT to coordinate extensively
with the contractor to determine when fines should be assessed.
There were times when average travel times were greater than
27 minutes for reasons other than construction activities. For
example, a runaway truck jackknifed in the work zone early on
in the project and caused a significant backup. Whenever a
non-construction delay was suspected, ADOT would work with the
contractor to review schedules to determine construction activities
that occurred during these periods of time to determine if the
contractor should be penalized for the delay experienced by motorists.
If the contractor could prove that construction activities should not
have impacted traffic flow, ADOT would not assess a penalty.
- Preparation for system deployment required communication and
coordination between the system vendor, the contractor responsible
for setting up wireless communications, the contractor, and ADOT.
- ADOT made extensive outreach efforts to communicate with the
public on all issues regarding the project. ADOT hired a public
relations firm to provide public outreach through a variety of means,
including public service announcements, cable television
announcements, radio media alerts, an informational telephone
number, and a website.
- ADOT's public relations firm mailed out newsletters (example shown
in Figure 5) three to four times per year to keep the public informed
about the project status and to provide answers to frequently asked
questions and concerns. In addition, the firm faxed weekly updates
to the 144 businesses and individuals who signed up for this service.
Figure 5 – Example of a Public Outreach Newsletter Distributed by ADOT
- ADOT's public relations firm provided a toll-free phone number
so that the public could reach a live person on weekdays between
8:00 a.m. and 5:00 p.m., and leave messages with questions or
concerns at night or on the weekends. The firm estimated that it
received an average of approximately 25 calls per week related to
the overall project schedule, specific delays, closures, and/or business
access. The most frequently asked questions related to specific
traffic delays. The firm received a few questions about the travel-time
system soon after it was installed, particularly regarding
privacy issues. Calls about privacy concerns dropped off after ADOT
addressed these issues in its public outreach newsletters.
- As a result of the increase in truck traffic on SR 68, the public
relations firm developed outreach documents especially for truckers,
and worked with the Arizona Motor Transportation Association to
distribute these to truckers at truck stops.
Maintenance
- The system supplier/vendor was able to perform system status
checks remotely, and the system required little maintenance.
According to the contractor, operating and maintaining the system
required approximately one hour per week. The system vendor
performed daily system status checks at the start of the project and
then weekly status checks throughout the rest of the project.
- The contractor had to periodically adjust and recalibrate the
cameras, as strong gusts of wind occasionally moved them out of
position. This problem would either be detected by the contractor
when reviewing the data or by the vendor when performing the
weekly status check of the data and the camera views. If contractor
staff noticed a problem with the data, they would contact the
vendor to determine if the camera views had changed, which
would indicate that they needed to be adjusted.
Back to Top
Results
System Performance
- The system functioned as intended. It was able to read approximately
60 percent and match approximately 11 percent of the license plates
photographed during the operation. ADOT considered this level of
performance to be adequate, both for this application and compared
to other license plate detection systems.
- The system went down near the beginning of the project due to
a power surge that damaged the 12-volt power supply. As a result
of this problem, the system was down for approximately 30 days
and ADOT was not able to assess the contractor's compliance with
the travel time incentive/disincentive clause for this time period.
After learning that the area was prone to power surges, the vendor
elected to install surge protection equipment when replacing the
damaged power supply.
System Evaluation
- Overall, both ADOT project managers and the contractor were
satisfied with the performance of the system and with the concept
of the travel time incentive/disincentive clause, though no formal
system evaluation was performed.
- For the most part, the contractor was able to maintain traffic
flow through the project according to the ADOT time-specified
requirements. The contractor was charged only $14,857 against the
$400,000 travel time bonus incentive at the end of the project,
thereby earning 96 percent of the bonus fund.
Benefits/Impacts
Mobility
- The contractor responded to the travel time incentive/disincentive
clause by limiting the number of flagging stations in the work zone
and by limiting the duration of directional closings to two to three
minutes at most. Both of these actions were taken to minimize
the impact of the construction on motorists.
- The contractor worked with ADOT and ADOT's public relations firm
to schedule work periods to reduce adverse impact on motorists.
For example, they worked together to determine the blasting
schedule by studying traffic volumes and surveying the casinos in
Laughlin about the times of their shift changes. After plotting
the casinos' shift changes along with the traffic volumes on SR 68,
they determined that the best time for blasting would be between
8:00 and 9:00 pm.
Safety
- A secondary benefit was reduced exposure of workers to traffic.
The contractor scheduled work to be performed in close proximity
to travel lanes during periods of low traffic volume to minimize
their disincentive fee.
Public Reception/Reaction to the System
- Motorists initially voiced concern about privacy issues due to the use
of cameras to photograph license plates. This issue was addressed
by informing the public, through the use of newsletters and other
public outreach methods, that the system immediately encrypts
all license plate numbers before archiving them so that no actual
license plate information is retrievable. This action ultimately eased
any privacy concerns of the public.
- Although the contractor mounted the light and camera system
behind construction signs to avoid causing distraction to motorists,
some motorists complained that the light was distracting at night.
These complaints diminished after the contractor adjusted the angle
of the lights and ADOT educated the public about the purpose of
the lights.
- ADOT received a great deal of positive feedback from the public
through e-mails and letters of appreciation. The public seemed
genuinely pleased that the delays were not as bad as might be
expected along such a highly traveled corridor. Many also expressed
satisfaction with the level of outreach related to construction
activities and schedules that ADOT provided throughout the
duration of the project.
Obstacles Encountered and Lessons Learned
General
- The contractor felt that having the incentive/disincentive clause in
the contract forced the crew to pay closer attention to the impacts
that their construction would have on the traveling public.
- ADOT felt that agencies considering a travel-time incentive program
should consider requiring a shorter reporting time frame to provide
a more realistic calculation of average travel times through the work
zone. They felt that 10-minute intervals would have been more
realistic.
- ADOT also felt that the maximum travel time used to calculate the
disincentive fee should have been closer to the average time it took
to travel the project limits before construction.
- ADOT and the contractor both felt that this system worked well in
a rural setting, but were unsure how well it would perform in a more
urban setting with a greater number of access points. However, the
same type of system is being used successfully in an urban setting
on the Coolidge Bridge Reconstruction Project in Massachusetts.
In this setting, a license plate match rate of 10 to 20 percent has
been sufficient for determining average travel times. The system can
identify vehicles that exit the road and return a short time later as
outliers by setting a threshold and automatically removing any travel
times from the data set that are greater than a specified percentage
over the average travel time. Therefore, access points within the work
zone do not pose an insurmountable problem for this type of system.
System Deployment and Operations
- The main challenge ADOT encountered with the surveillance system
was that it was difficult for the system to read license plates when
the camera was facing directly into the sun. Fortunately, this was
only a problem for approximately one hour each day, so it was a
minor concern.
- A traffic camera was stolen during the course of the project, and it
took approximately two weeks to replace the camera. The contractor
responded by purchasing an extra camera in case it would be needed
in the future, and by welding the cameras to the sign structures
and installing chains and padlocks to secure them. ADOT project
managers felt that it would have been beneficial to specify a
requirement in the contract for the contractor to keep an additional
camera on-hand to be able to respond more promptly to
unexpected situations.
- ADOT project managers found it to be somewhat time consuming
to process the travel times received from the contractor. ADOT felt
that this procedure could be more automated in the future.
Communications
- A major obstacle ADOT encountered in using this system was the
remote project location and limited infrastructure, which made
system communications challenging. ADOT had initially hoped to
use solar power for the cameras and lights, but found this option
to be prohibitively expensive. Therefore, camera locations were
limited by the availability of public utilities for power in this remote
location. Because the project was located in a mountainous region,
additional equipment was needed to provide the communications
required by the point-to-point microwave technology. The terrain
of the region required installation of repeaters to relay signals from
the roadside sites to the main transmitter for the line-of-sight
technology.
- Some electrical problems occurred at one point during the project,
and the system was down for approximately 30 days while
technicians repaired the problem. During this period, ADOT could
not assess compliance with the travel time incentive/disincentive
clause due to lack of data. As a result, ADOT felt that future
contracts should include a penalty stating that the contractor will
incur a fee if the system is down for more than 48 hours.
"The travel time incentive program
truly minimized the construction impacts to the traveling public
and commuters."
— Jennifer Livingston, Sr. Project Manager ADOT
(Former Resident Engineer -
Kingman District)
Back to Top
Conclusion
The use of an ITS application on State Route 68 in rural Arizona was
a success for all involved. Both the contractor and the ADOT project
managers were pleased with how the system worked, and ADOT
received a great deal of positive feedback from the public. With the
use of the travel-time system and the incentive/disincentive clause,
the contractor was forced to be innovative in managing construction
efforts to minimize impacts on the traveling public. This case study
is one example of how ITS is being implemented across the nation to
help agencies better manage traffic while performing necessary
infrastructure improvements.
Arizona DOT contact for this project
Jennifer Livingston, P.E.
Sr. Project Manager
Arizona DOT
Statewide Project Management
1801 S. Milton, MD F500
Flagstaff, AZ 86001
928-779-7591
jlivingston@dot.state.az.us
Back to Top
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This Document Is One in a Series of Products That Address ITS Issues Pertinent to a Variety of Audiences
- Elected and Appointed Officials
- Senior Decision Makers
- Transportation Managers
- Technical Experts
Representing:
- States
- Cities
- Counties
- Transit Properties
- Toll Authorities
- Emergency Service Providers
- Metropolitan Planning Organizations
- Additional Transportation Stakeholders
ITS Topics Addressed in This Series:
- Commercial Vehicle Operations
- Emergency Services
- Enabling Technologies
- Emissions Management
- Freeway and Arterial Management
- Highway Operations and Maintenance
- Planning and Integration
- Real-Time Traveler Information
- Transit, Toll, and Traveler Information
- Weather Information for Travelers and Maintenance
- Work Zones
For a current listing of available documents, please visit our website at:
http://www.its.dot.gov
Intelligent Transportation Systems
U.S. Department of Transportation
400 7th Street SW
Washington, DC 20590
Federal Highway Administration
Room 3416, HOIT-01
Phone: (866) 367-7487
Facsimile: (202) 493-2027
FHWA-HOP-04-032
EDL# 14001
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