A paper prepared for the January 22-28, 1995 meeting of the Transportation Research Board reported on the success of a Colorado Department of Transportation (CDOT) pilot program. The program put courtesy patrols on Denver-area freeways to provide incident management during rush hours and to attempt to reduce congestion. CDOT contracted with the University of Colorado at Denver to evaluate the program. Peggy Cuciti of the University's Center for Public Private Sector Cooperation and Bruce Janson of the College of Engineering wrote the resulting report entitled "Incident Management Via Courtesy Patrol: Evaluation of a Pilot Program in Colorado." This article describes the courtesy patrol program and summarizes the evaluation of its effectiveness.

Background

The Intermodal Surface Transportation Efficiency Act of 1991 (ISTEA) encourages state highway agencies to make more efficient use of existing highways and discourages new highway construction projects. The challenge is to develop alternate methods of reducing traffic congestion, especially in areas like Denver, Colorado, where air quality is out of compliance with national standards.

Traffic congestion contributes to poor air quality; moreover, traffic congestion translates into losses for society. As speeds decrease, trip times increase. Congestion on urban freeways results in an estimated annual loss of two billion vehicle hours. Traffic congestion increases fuel consumption. It also increases collision rates. According to Cuciti and Janson, the yearly national cost of traffic congestion on urban freeways is $16 billion.

Congestion is not always the unavoidable result of too many vehicles for the designed capacity of the freeway. Research has shown that certain "incidents" on or along the roadway account for as much as 60 percent of urban freeway traffic congestion. These incidents include:

(1) major accidents that tie up several lanes or entire freeways for hours, (2) minor accidents and stalled vehicles that block only one lane for short durations, (3) vehicles stopped in shoulders, (4) spilled loads, (5) construction, utility and maintenance activities and (6) special events that generate heavy traffic volumes.

The Federal Highway Administration estimates that when an incident blocks one lane of a three-lane roadway, traffic capacity reduces by half. Even when the incident is not on the road (e.g., on the shoulder of the roadway), traffic capacity reduces by a fourth. The latter capacity reduction results from the "gawking effect," when people slow to look at an incident. Clearing the incident from the roadway returns the capacity to normal; the more quickly this is done, the less congestion occurs. According to estimates from the California Department of Transportation, each minute saved in clearing away an incident yields a reduction in motorist delays of four to five minutes.

History of the Colorado Program

In 1991 the Colorado Incident Management Coalition (CIMC) began evaluating traffic congestion on Denver-area freeways. This multi-disciplinary group (composed of agencies and corporations involved in traffic management and incident response) found severe traffic congestion during morning and evening rush hours. Since projections suggest vehicle miles traveled in the Denver metro area will increase from the present 34 million to 65 million by 2010, traffic congestion problems will get worse.

Given the expense and political complications of expanding existing freeways or developing new alternate routes, the CIMC suggested better incident management as a viable strategy to improve traffic flow, minimize motorist delays, and reduce air pollution. The coalition recommended an incident management program designed "to reduce incident detection and verification time, reduce incident response time, reduce incident clearance time, develop effective incident scene management, and provide timely and accurate information to motorists." Implementation of the entire comprehensive plan would take time and would require changes in the law and extensive cooperation among jurisdictions. The courtesy patrol program, however, was a portion of the plan that could stand alone and that CDOT could set in motion fairly quickly.

Courtesy Patrol Pilot Program

The Colorado courtesy patrol pilot program involved both the Colorado State Patrol (CSP) and the American Automobile Association (AAA) in delivering services. The program also enlisted the cooperation of various organizations. Metro Traffic Control and commercial media helped with communications. The Denver Police Department coordinated with program personnel on traffic law enforcement and emergency response services. Private businesses provided taxi services for stranded motorists and parking lot space for disabled vehicles.

The pilot program operated six courtesy patrols during rush hours--from 6:00 a.m. to 9:00 a.m. and from 3:30 p.m. to 6:30 p.m. Monday through Friday. Patrols covered about 27 miles of I- 25 and a short section of I-70 where it intersects I-25. CDOT chose these times and places because of heavy traffic congestion and high need for improvement.

CSP used four-wheel-drive vehicles equipped with heavy push bumpers and removable magnetic courtesy patrol signs on the doors and roofs. AAA used Class A red tow trucks also equipped with magnetic courtesy patrol signs. Signs on vehicle roofs helped airborne traffic observers locate courtesy patrol units.

CSP used volunteer off-duty officers to cover the six hours per day, five days a week required for the courtesy patrol. The officers received time-and-a-half pay for the work. AAA adjusted schedules and staffed courtesy patrol units with their regular drivers working for regular wages. Personnel received briefing on the procedures and responsibilities of the courtesy patrol. No other training beyond that provided by CSP and AAA to their own personnel was deemed necessary.

During the designated times, two patrol units operated in each of three zones established on the freeways. CSP provided two units, and AAA provided four. Their responsibility was "to assist disabled vehicles that are blocking lanes of traffic or are on the shoulder of the roadway." Although units sometimes helped at collision sites, their emphasis was on non-collision incidents.

Types of Problems

During the six months from August 28, 1992 through February 26, 1993, the courtesy patrol wrote up 3,393 incidents--an average of 27.6 incidents each day the patrol was on duty. About 28 percent of these incidents resulted from flat tires, running out of gas, and radiators overheating. Another 22 percent of responses were for abandoned vehicles, a problem the patrol could do relatively little to correct. Other incidents included: miscellaneous mechanical problems (34 percent), collisions (9 percent), debris on the road (1 percent), and miscellaneous other (6 percent). The "miscellaneous other" category incorporated a variety of causes, including some that involved the driver rather than the vehicle (e.g., the driver pulled over to read a map or use a cellular telephone).

Cars made up 61 percent of vehicles involved in incidents, and pickup trucks or vans accounted for an additional 29 percent. The rest were buses, trucks, or vehicles with trailers--larger units that presented more difficulty for the patrols if they had to be moved.

Slightly more incidents happened on Mondays and Tuesdays than on Thursdays and Fridays, and 55 percent of reported incidents happened during afternoon rush hours. Involved vehicles were not blocking a lane of traffic in 72.7 percent of the incidents. Vehicles were found on the right shoulder rather than the left in 63 percent of the cases. The incidents most likely to result in vehicles blocking traffic lanes were collisions and mechanical problems.

Courtesy patrol personnel located about 90 percent of the incidents themselves, while Metro Traffic Control supplied the rest of the leads. When patrol personnel had to respond to information from an outside source, it took seven minutes on average for a patrol vehicle to arrive at the scene.

Types of Services Rendered

To fulfill their mission of decreasing the time involved in clearing an incident from the roadway, courtesy patrol personnel were prepared to provide certain services immediately. The authors noted that courtesy patrol staff were:

. . . prepared to fix flat tires, provide a free gallon of gasoline, fill radiators with water, jumpstart stalled vehicles and fix some other minor mechanical problems. If vehicles ha[d] more serious or difficult-to-identify mechanical problems, the courtesy patrol [could] move the vehicle or call for other assistance.

In addition, patrol personnel would use emergency lights to protect an incident scene.

In 14 percent of incidents, motorists refused courtesy patrol service, because other assistance was on the way or the motorist felt the incident was under control. When the patrol did render assistance, they would sometimes, for example, push a vehicle out of a traffic lane and then provide gasoline. Therefore, the average motorist received more than one type of assistance. The patrol reported providing an average of 1.16 services per incident.

Courtesy patrols helped in the following ways: fixed flat tires in 72 percent of those incidents; provided a gallon of gas to 81 percent of vehicles in need; directly serviced overheated radiators in 51 percent of cases; rendered miscellaneous mechanical service to 20 percent of disabled vehicles; cleared debris 87 percent of the time, protected the scene of a collision in 66 percent of cases; and pushed or towed disabled vehicles about one-fifth of the time.

As an average for all vehicles, it took the courtesy patrol 9.9 minutes to move a disabled vehicle from the traffic lane. The average time for moving vehicles that were able to resume travel on their own was 8.6 minutes, while vehicles needing to be pushed or towed took 12.7 minutes.

According to information provided by courtesy patrol personnel, they "cleared" 80 percent of the incidents to which they responded. This figure does not include abandoned vehicles.

Effectiveness of the Courtesy Patrol Pilot Program

Four phases make up the total amount of time elapsed from the occurrence of an incident that causes traffic congestion to the return of normal traffic flow. The detection phase is the time from when the incident happens until someone who can respond learns about it. The response phase is the time it takes for someone to arrive at the scene. The service phase is the time elapsed from the arrival of assistance until the incident is sufficiently cleared so that normal traffic capacity exists. The queue dissipation phase (also called traffic restoration time) is the time it takes, once capacity has been restored, for traffic to begin moving normally for that location at that time of day.

Vehicle delays will vary with the amount of time involved in each of these phases for a particular incident. Traffic volume at the location during the incident will also affect delay times and will hinge on the availability of alternate routes for vehicles approaching the incident. In addition, the number of lanes blocked and the number of lanes open to go around the blockage influences the congestion caused by an incident.

Using industry formulas to compare estimated traffic delays caused by an incident when the courtesy patrol was in operation and when it was not, this research attempted to determine to what extent operating the courtesy patrol decreased traffic congestion. To learn the average length of time it took for an incident to be detected and cleared before the courtesy patrol came on the scene, researchers used data from Metro Traffic Control, a private company that collects traffic data for Denver television and radio stations.

Metro Traffic Control had no information on the average time required after an incident happened to notify someone who could respond. Although the authors felt response times were faster when six courtesy patrol units were cruising the area looking for incidents, they lacked comparative data to include in study results. Therefore, they used an average detection time of 5.5 minutes, the approximate time it took for courtesy patrol personnel to visually scan all of their assigned zone. Conclusions about improvements in incident-clearance time assumed there was no change in the length of time required to detect an incident with or without courtesy patrols.

Assuming no decrease in detection time, researchers used available data on response and service times to compare total incident duration with and without courtesy patrols in operation. Courtesy patrols cleared incidents blocking a lane of traffic an average of 10.5 minutes faster than comparable incidents were cleared without courtesy patrol units on duty. For incidents that did not block a lane, average incident duration time decreased by 8.6 minutes.

Researchers then computed the time savings for motorists represented by shorter incident durations. Computations based on high estimates of traffic volumes and lengths of vehicle delays for various types of incidents led the researchers to conclude that the courtesy patrol saved an average of 98 vehicle hours of delay for each morning incident they cleared and 75 hours of delay for each afternoon incident. Using low estimates, the savings dropped to 78 vehicle hours for morning incidents and 71 for afternoon incidents.

The final computation allowed evaluation of the courtesy patrol's cost effectiveness--determining how much money the program saved compared to the expense involved in running it. Here researchers used an average figure for the value to society of each hour saved by getting people and goods moving more quickly. That average is $10 per vehicle hour. Based on high estimates of the decrease in hours of motorist delay, the program saved approximately $2,027,850 by reducing motorist delays. Based on the low estimates, the savings was about $1,757,930. The authors pointed out that these figures did not include the direct savings motorists gained when they received services that solved their problems without having to pay for towing or repair.

The estimated cost of operating six courtesy patrol units for six months was between $120,000 and $168,000. The low figure used AAA costs for all six units, and the high figure used CSP costs. AAA costs were lower because they paid regular wages rather than the time-and-a-half wages paid by the CSP to off-duty personnel. The low figure assumed that if this pilot program were implemented on a regular basis, it would be staffed by personnel receiving wages lower than the $31/hour paid to off- duty CSP personnel.