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May/June 2002
Arizona Tackles Work Zone Delays
by Alan Hansen
If you're having trouble minimizing traffic delays during construction projects (and who isn't), then you may discover some ideas in two innovative programs developed by the Arizona Department of Transportation (ADOT)—a motorist assist patrol and a travel-time incentive program. ADOT used the new approaches to minimize motorist delays while reconstructing a 13-mile (21-kilometer) section of State Route 68 (SR-68). The project started in July 2000 with a partnering workshop between the contractor and ADOT, and all of the pavement was in place by the end of April 2002.
Although SR-68 is a rural corridor cutting through high-desert landscape and the Black Mountains, highway officials in Arizona consider the road to be a major commuter route. It serves motorists traveling between Kingman and Bullhead City on the Colorado River near the State's western border. In addition to commuter traffic, trucks comprise 7 percent of the vehicles on SR-68, and a significant number of recreational users also travel the corridor. The construction project started at about the mid-point of SR-68 and went to Bullhead City.
ADOT's Kingman district engineer Debra Brisk developed the motorist assist patrol and the travel-time incentive program specifically for this project. ADOT resident engineer Jennifer Livingston conducted a site visit in May 2001 when the project was approximately 35 percent complete. "The traffic management tools," says Livingston, "truly minimized the construction impacts to the traveling public and commuters."
Logo for the Motorist Assist Patrol.
Motorist Assist Patrol
The motorist assist patrol (MAP) consisted of a vehicle and driver equipped with equipment and supplies that could aid stranded motorists get back on the road or call for additional assistance if needed. Each MAP vehicle was outfitted with traffic control devices, water, gasoline, flares, jacks, and lighted arrow boards.
The Motorist Assist Patrol helps a stranded motorist in a recreational vehicle.
In addition to helping the motorist safely back on the road, the MAP also kept the roadway clear, identified incidents, and maintained smooth operations while the highway was under construction. The drivers of the MAP vehicles were trained as security guards, but they dressed in typical construction-type clothing, including hard hats and safety vests.
The contractor, who operated the MAP from 4 p.m. to 6 a.m. on weekdays and around-the-clock on weekends, hired a private security guard service. They operated the MAP vehicles during the hours when construction was not going on. During construction hours, the MAP was considered unnecessary since plenty of people were available to assist motorists.
This construction map shows turn lanes, raised medians, new road alignments, open medians, and concrete barriers.
Because the MAP operated at off-peak hours and the MAP drivers approached stopped vehicles and sometimes encountered people acting suspiciously, the contractor determined that trained security guards would be safer MAP drivers. The security guard training also helped the drivers know how to approach stranded motorists in a professional manner that put the motorist at ease.
Between the program's inception in October 2000 and April 2002, the MAP vehicles assisted 963 stranded motorists. The majority of the travelers were stranded due to mechanical failure, probably caused by the high-desert temperatures and the 6-percent grade that is characteristic of much of the segment of road that was under construction. Of these motorists, 68 percent were able to get back on the road with the assistance of the MAP only. Further assistance, such as towing services, were called in the cases of the other 32 percent of the motorists needing help.
"The commitment to safety and cooperation … by the SR-68 team was impressive," says Lieutenant Ron DeLong of the Arizona Department of Public Safety (DPS). "The Motorist Assist Patrol was very helpful to DPS and the traveling public. ADOT and the contractor also responded quickly to other travel and safety issues throughout the project."
Travel-Time System Incentive Program
The SR-68 project also implemented a travel-time system that measured the consistency of the time it took for motorists to travel through the construction work zone. Prior to construction, the average travel time for this segment, which has a posted speed limit of 55 miles per hour (89 kilometers per hour), was 17 minutes. During construction, traffic control measures and reduced posted speed limits of 35 to 45 mph (56 to 72 km/h) increased the corridor travel time to approximately 21 minutes.
The contract included a provision that during construction, the average travel time would not exceed 27 minutes. The onus was on the contractor to measure the travel time and ensure that the average travel-time goals were met. The contract provided for a $400,000 travel-time incentive budget item that was to be reduced if the target travel-time average was exceeded. The travel times were taken 24 hours a day, 7 days a week, and were averaged over 10-minute periods. If three consecutive 10-minute periods were clocked at over 27 minutes, the contractor was charged $21.50 per minute per lane.
Any funds left in the travel-time budget are to be paid as profit to the contractor. If the contractor were unable to maintain the target travel time during construction, the entire $400,000 could be depleted, and the contractor would be responsible for paying for the additional travel-time delay.
As the best way to measure the travel time through the construction corridor, the contractor chose to deploy a license plate reader system developed by a British company, Computer Recognition Systems, which has its U.S. headquarters in Boston, MA. The system uses a camera and a light source to capture the license plate images of passing vehicles.
The light used to illuminate license plates for the Travel-Time System Incentive Program.
This digital camera was used to read license plates.
Image recognition software takes the license plate number from the picture, encrypts it, and then sends it to the central computer at the contractor's office through a high-speed data connection. The system is optimally designed to capture license plate readings at 45 to 55 mph (72 to 89 km/h).
A second camera at the far end of the construction zone takes a second picture, encrypts that license plate number, and sends it to the central computer on a high-speed connection. The central computer then matches up the license plates that enter and exit the limits of the construction project and calculates the times for the motorists' trips.
The light used to illuminate license plates was placed with the digital camera in the background.
The contractor placed a total of four cameras on the project, one each at the entrance and exit of the construction in each direction. The cameras were mounted behind construction signs to keep them from distracting the motorists. Each of the four locations included a camera on one sign assembly and a steady burning light on a second assembly, each positioned to capture license plate readings from passing vehicles. The lights, which operated 24 hours a day, were necessary to read and recover the license plate numbers, especially on license plates covered by motorist-installed plastic license plate covers.
The project participants considered using radar systems throughout the corridor to implement the travel-time system. Such technology would give single-point traffic speeds but would not offer direct measurement of corridor travel times.
As with many things, the terrorist attacks on September 11, 2001, affected the SR-68 project. The US-93 route across the Hoover Dam, which is the other major route for vehicles traveling between Arizona cities and Las Vegas, was closed to truck traffic. All of the traffic was routed over SR-68 and through the construction project. At the time of the terrorist attacks, the contractor had been very successful in meeting the average travel-time goal, resulting in only $9,594 being drawn from the travel-time fund. The final resolution of the travel-time goals that were exceeded between September 11 and the end of the construction project is still under negotiation.
The license plate reader system was able to match around 11 percent of the license plates photographed at the start with those photographed at the finish of the corridor, a statistically adequate percentage for measuring the average travel time. The license plate reader system was fairly expensive to operate. The system requires high-speed data connections, which cost about $700 per month for a high-speed communication line capable of transmitting the travel-time information from the far end of the project versus about $200 per month for a wireless connection, which could have been used for the short distance connection on the Kingman end of the project. The monthly expense for electricity was approximately $100. Once the project is completely finished, the license plate reader system will be the property of the contractor.
The contractor placed signs on the backs of the camera and light to reduce driver distraction.
The license plate reader system has had its detractors and its share of controversy. Since the lights were on constantly, early in the project some motorists complained that the light positioned in the opposite direction to their travel distracted them. These complaints diminished after the contractor redirected the lights, and ADOT engaged in public outreach and education about the purpose of the lights.
After one of the cameras was stolen, the contractor welded the cameras to the sign structure and installed chains and padlocks. As construction proceeded and travel lanes were moved, the cameras and lights had to be adjusted continuously so that the license plates of the cars were clearly in the field of view.
Some motorists also raised privacy complaints at the start of the project; however, the central computer does not maintain any of the license plate numbers after they have been initially encrypted. The dissemination of information about the license plate reader system and the fact that it does not store license plate numbers eased the privacy concerns.
Benefits to Date
Both of these programs make the SR-68 project a model for innovative work zone enhancements. ADOT provided comment cards to the many stranded motorists who were helped by the MAP patrols. Nearly 50 percent responded, all of whom made positive comments about their rescuers. Clearly, both programs are very popular with members of the traveling public, who find their travel delays reduced.
One resident of Bullhead City says, "I commute daily from Bullhead City to Kingman; what could have been a real nightmare during construction was no more than a slight headache. I smile every day now when I'm traveling to and from work."
The travel-time incentive program is not as visible to the public as the MAP vehicles, but motorists still enjoy the benefits of both programs. Due to the travel-time incentive program, the contractor limited the number of flagging stations throughout the construction project and scheduled work in such a way that the adverse impact on motorists was reduced.
ADOT made extensive outreach efforts to communicate with the public regarding the project, including hiring a public relations firm and developing public service announcements, cable television announcements, radio media alerts, an information telephone number, and a Web site. These venues enabled motorists who use the corridor to express their opinions on the project. Those who responded reported that the construction work zone did not affect their travel through the corridor significantly. In addition to limiting travel delays, work zone programs such as these help improve transportation system efficiency, increase work zone safety, and provide a better working relationship between the State DOT, the contractor, and the community.
The contractor's Motorist Assist Patrol vehicle was a white pick-up truck with flashers and a logo with the words, "State Route 68 Motorist Assist Patrol."
Alan Hansen is the assistant planning and research engineer for FHWA's Arizona Division. He has managed the Research and Intelligent Transportation System programs for the Arizona Division since May 1997. He serves on a number of FHWA task forces, including The ITS Program Assessment Working Group, the Operations Council, 511 task force, and the Linking Planning and Operations Working Group. His involvement in these task forces, FHWA's national training program, and other organizational and policy development activities has provided Hansen the opportunity to work with professionals throughout the U.S. Department of Transportation as well as external organizations. Hansen joined FHWA in 1987, and his career has included assignments in Federal aid, design, construction, intelligent transportation systems, planning, and research. He has a bachelor's degree in civil engineering from California State University Fresno, and he is a registered professional engineer in Arizona.
For more information, call the project's phone number, which will remain active, at 888-887-0565, or call Jennifer Livingston at 928-779-7591.
Other Articles in this issue:
Arizona Tackles Work Zone Delays
A Hallmark of Context-Sensitive Design
Do Better Roads Mean More Jobs?
Exciting Opportunity for ITS Work
Benefitting from LTPP—A State's Perspective
