Service Patrol Research Articles

A simulation approach for quantifying the cost-effectiveness of freeway service patrols programs

Freeway Service Patrols is one of the main components of highway Incident Management (IM) programs because of its low-cost feature and effectiveness in incident detection, mitigation and clearance. This paper presents a methodology to quantify freeway service patrol programs' cost-effectiveness with limited operation data using microscopic simulation. Simulation models are developed to test benefits of patrol service by comparing 'with' and 'without' scenarios under various traffic conditions. The analysis results from a case study indicate that patrol operations may have a significant impact on incident detection process, especially for incidents of low severity, such as debris and abandoned vehicles.

Optimal Fleet Allocation of Freeway Service Patrols

As one component of traffic incident management systems, freeway service patrols (FSP) facilitate quick removal of incidents through faster response and reduced clearance time. This paper is to investigate how to allocate tow trucks among patrol beats to maximize the effectiveness of the FSP services. A min–max bi-level programming model is proposed to determine an optimal fleet allocation that minimizes the maximal system travel time that incidents may incur. A heuristic iterative solution algorithm is proposed to solve the model. Both the model and the algorithm are demonstrated and validated through a numerical example.

Tools for Supporting Implementation Decisions of Intelligent Transportation System

Planners and engineers may consider both conventional capacity improvements and intelligent transportation systems (ITS) to address transportation problems. Examples of ITS include freeway service patrols, advanced vehicle location systems, and certain elements of employee transit pass programs, each with various advantages. Details of a system to help planners and engineers make informed decisions about ITS deployment are provided. ITS Decision is designed to provide comprehensive information about state-of-the-art ITS technologies in a relevant form—the user can access desired information without sifting through irrelevant material. In addition, ITS Decision offers innovative tools to help users identify ITS appropriate for particular transportation problems. An expert system queries the user about specific conditions, diagnoses the problem, and suggests ITS remedies. The case-based reasoning tool lets users match historical cases that are most similar and see the effects. Given the still limited penetr...

Tools for Supporting Implementation Decisions of Intelligent Transportation Systems

Planners and engineers may consider both conventional capacity improvements and intelligent transportation systems (ITS) to address transportation problems. Examples of ITS include freeway service patrols, advanced vehicle location systems, and certain elements of employee transit pass programs, each with various advantages. Details of a system to help planners and engineers make informed decisions about ITS deployment are provided. ITS Decision is designed to provide comprehensive information about state-of-the-art ITS technologies in a relevant form—the user can access desired information without sifting through irrelevant material. In addition, ITS Decision offers innovative tools to help users identify ITS appropriate for particular transportation problems. An expert system queries the user about specific conditions, diagnoses the problem, and suggests ITS remedies. The case-based reasoning tool lets users match historical cases that are most similar and see the effects. Given the still limited penetration of ITS into appropriate settings, the expert system and case-based reasoning tools are meant to stimulate greater deployment of promising technologies in localities that have not adopted such systems.

Simulation-based evaluation for urban expressway ramp metering: a Madison Beltline case

The aim of this paper is to evaluate the effectiveness of the ramp metering on the Madison Beltline, highway section from Park St. to Gammon Rd. The overall network performance was evaluated under “with” and “without” ramp metering conditions by CORSIM (CORridor SIMulation). Three evaluation plans were developed. The first plan is to use speed profile of both mainline and ramps on Beltline freeway with or without ramp metering situations. The second is to evaluate ramp metering with an incident taken place The third to evaluate the effectiveness with service patrol implemented. The results show that travel speed, with metering, increases up to 10% (AM) and 8% (PM) on the westbound and 0.2% (AM) and 0.7% (PM) on the eastbound Beltline, respectively. Most notably, the travel speed between Fish Hatchery Rd. and Midvale Rd. in the westbound direction is increased by 16% (AM) and 39% (PM) respectively. While the speed of mainline increased the speed of ramp of whole sections has been decreased by 16% AM and 18% PM (westbound), and 7% AM and 3% PM (eastbound) respectively. The ramp speed with ramp metering is reduced by 50% compared to that of without ramp metering. In incident case with ramp metering, the speed was higher (17% AM, 7% PM) than that of without ramp metering. With both ramp metering and service patrol implemented, the speed has been greatly increased up to 19% (AM) 1.6% (PM), respectively. This implies that the effectiveness of service patrol is synergistically enhanced with ramp meter ing implementation. In conclusion, the ramp metering on the Madison Beltline gives a positive impact on the travel speed of Beltline and thereby reduces traffic congestion more or less.

Secondary Accident Rates on Los Angeles Freeways

There is a prevailing assumption that Freeway Service Patrol (FSP) programs improve safety for unassisted motorists by reducing the likelihood of secondary accidents. This research identifies 84,684 accident records from the California Highway Patrol’s First Incident Response Services Tracking system, and subjects these data records to a sequence of filters that check for incrementally more stringent conditions consistent with secondary accidents. This paper shows that secondary accidents on Los Angeles freeways are much less frequent than suggested in the transportation engineering literature. Avoiding secondary accidents provides only a small incentive to deploy FSPs, but the expected benefits associated with reducing already low secondary accident rates may still be sufficient to justify accounting for these costs.

Method for Priority-Ranking and Expanding Freeway Service Patrols

Freeway service patrols (FSPs), classified as part of intelligent transportation systems, are programs that use roving vehicles to patrol congested and high-incident sections of freeways; they help to smooth traffic flow by aiding stranded motorists and assisting in incident clearance. Many major urban areas currently have patrols, and most medium-sized urban areas are following suit. The success of FSPs has resulted in frequent requests for service expansion. However, the decision on where to put the next patrol is becoming more difficult because an assessment of greatest need typically indicates that high-priority areas already have the service, whereas the possible effects of the service are often indistinguishable on lower-priority facilities. A new approach was developed to help determine the most beneficial locations for patrol deployment by using expanded placement criteria. North Carolina was used as a case study. Analysis of three incident and crash indexes was combined with spatial analysis, incident type distributions, average hourly freeway traffic volumes, and incident delay estimations to identify, evaluate, and compare candidate facilities for FSP expansion. Results of the research were incorporated into a decision support tool that allows easy planning and operational assessment of candidate sites by comparing performance values between sites, modeling the effect of FSPs, and estimating their key potential benefits. By using the tool, decision makers can quickly assess the needs of different facilities and make an informed, cost-effective decision on where to implement the next service patrol.

Methodology for Measuring Recurrent and Nonrecurrent Traffic Congestion

A methodology is presented for estimating and predicting the total annual traffic congestion attributable to recurrent and nonrecurrent congestion. The methodology is applicable to freeways, conventional highways, and urban streets. The methodology is sensitive to improvements in facility surveillance and freeway service patrol strategies. Recurrent congestion is estimated by using Highway Capacity Manual speed-flow curves and data on facility demands, free-flow speeds, and capacities. Nonrecurrent congestion is estimated in terms of annual vehicle hours of delay caused by weather, work zones, incidents, and so forth. The methodology employs incident probability trees, incident duration (sensitive to surveillance and response times), and estimates of remaining capacity during incidents to estimate incident delay. Weather-and work-zone-related delays are estimated on the basis of frequency of occurrence and estimates of capacity reductions during periods of bad weather and work-zone activity. The methodology has been implemented in a spreadsheet.

Development of Tennessee’s Freeway Service Patrol (HELP) Program

Many studies have been conducted to describe and evaluate the benefits of freeway service patrols, but much less is known about the planning and institutional development of such programs. This case study describes the implementation of Tennessee’s freeway service patrols. In 1998 the Tennessee Department of Transportation (TDOT) began planning for patrols to operate on the highest-volume freeways in the state’s four largest cities—Chattanooga, Knoxville, Memphis, and Nashville. After a staged implementation plan, TDOT has successfully implemented the patrols, known as HELP, in all four cities while also moving forward with related intelligent transportation system and incident management initiatives. Five aspects of program development are described that have been especially important to the success of the program—teamwork, attention to human resource issues, comprehensive training, first-rate vehicles and equipment, and communications.

Feasibility of Using Freeway Service Patrol Trucks as Probe Vehicles

This research assessed the feasibility of using trucks in an existing Los Angeles Freeway Service Patrol (FSP) fleet as probe vehicles to measure ambient speed on freeway segments. Floating car speeds were the basis of comparison with other speed data. Loop detector-based segment speeds and FSP truck speeds were compared against a common baseline. Unfortunately, FSP truck speed data available from the existing system are of insufficient quality to estimate ambient speeds. Comparisons between floating car and FSP truck speed records reveal that FSP truck speed is a poor measure of floating car (ambient) speed. FSP truck speed records underestimate floating car speeds overall, and covariance between the two is weak.

Simulation Model for Evaluating and Improving Effectiveness of Freeway Service Patrol Programs

Nonrecurrent congestion caused by highway incidents is a major concern for transportation agencies and millions of road users in most metropolitan areas in the United States. As a low-cost approach to incident management, freeway service patrol programs have gained wide popularity. Although there are many such programs in different parts of the country, there is not much effort to design such programs systematically so that better results can be obtained through efficient use of existing resources. A simulation model has been developed that can be used for designing a new freeway service patrol program configuration as well as improving operations of existing programs. The Hoosier Helper program in northwest Indiana is presented as an example of the model’s application. The information provided in this study would be useful for evaluating and improving the effectiveness of similar patrol programs in other metropolitan areas in Indiana and in other states.

Intertechnology Effects in Intelligent Transportation Systems

The expected benefits of varying combinations of intelligent transportation system applications, such as freeway service patrol, changeable message signs, and ramp metering, were examined. The research analyzed the simulated results of a stylized network in a microscopic traffic simulator. The traffic network included parallel roadways, ramp meters, and changeable message signs. These technologies were tested in various combinations. The effectivenesses were determined, and a measure of inter-technology economies was defined. In brief, additional technologies were found to be subadditive, and more benefits came from each technology in isolation than from the bundling of each with other technologies.

Cost-Effectiveness Evaluation of Hoosier Helper Freeway Service Patrol

Hoosier Helper is an Indiana Department of Transportation sponsored roving freeway service patrol, providing free assistance to motorists stranded on portions of Interstate 80-94 and Interstate 65 in Northwest Indiana, which started on August 30, 1991. This paper presents a detailed evaluation of the Hoosier Helper freeway service patrol. Specifically, the study results will include a benefit-cost ratio for each of two distinct Hoosier Helper operating scenarios: Daytime patrol and 24-h patrol. The calculation of agency cost concerns an aggregation of equivalent annual investment cost, employee salaries and benefits, overhead cost, and maintenance cost for Hoosier Helper. The following components comprise the estimation of Hoosier Helper benefit: Nonrecurrent congestion delay savings, secondary crash reduction, and vehicle operating cost savings. The study yielded a 4.71:1 benefit-cost ratio for the daytime program operation and a 13.28:1 benefit-cost ratio for the 24-h program operation. The increase in benefit-cost ratio magnitude, brought about by Hoosier Helper's change to 24-h operation, clearly supports the program's operating strategy as it exists today.

Evaluating a Roadside Assistance Program: Penn-Lincoln Parkway Service Patrol

The results of a preliminary evaluation of the Penn-Lincoln Parkway Service Patrol are summarized. The Pennsylvania Department of Transportation contracts with a local towing company to operate the Service Patrol on the Penn-Lincoln Parkway (PA Route 60, U. S. Route 22, and Interstates 279 and 376) in the Pittsburgh metropolitan area. The Service Patrol, consisting of specially equipped tow trucks driven by specially trained drivers, provides assistance to disabled vehicles along the parkway, thus reducing traffic delays and congestion. Service patrol hours of operation are during the morning and afternoon peak travel hours. The length of highway included in the evaluation is approximately 32 km (20 mi). The evaluation compared data from the period January–April 1997 with incident data collected by the Pennsylvania State Police during the corresponding period in 1996. The data were analyzed to determine the effect of the Service Patrol on incident response times, incident clearance times, and incident-related congestion factors (i.e., vehicle-hours of delay, fuel consumption, and vehicle emissions). This evaluation yielded the following results: ( a) the Service Patrol reduced incident response times by approximately 8.7 min; ( b) the Service Patrol cleared incidents approximately 8.3 min faster than before implementation; ( c) the Service Patrol reduced hours of delay by approximately 547,000 h per year; ( d) total monetary savings resulting from implementation of the Service Patrol are approximately $6.5 million per year; and ( e) the public response to the Service Patrol is overwhelmingly favorable.

Los Angeles I-10 Field Experiment: Incident Patterns

The Los Angeles I-10 field experiment has produced a large, comprehensive database on incidents and freeway traffic flow characteristics. Field data on incidents were collected through observations of probe vehicle drivers over a 12.5-km (7.8-mi) freeway section. Supplementary information was collected from the California Highway Patrol computeraided dispatch (CHP/CAD) system and freeway service patrol logs. The incident patterns at the study area are described, and the major factors affecting incident frequency and duration are identified. Comparisons of the findings with other databases are discussed. The effects of incidents on traffic flow are also investigated using the empirical data to determine the proportion and characteristics of delay-causing incidents.

ITS Impacts on Safety and Traffic Management: An Investigation of Secondary Crash Causes

Freeway service patrols, an increasingly popular choice in combating the effects of traffic incidents on freeway operations, have been known to reduce incident response and clearance time. This reduction can help alleviate the delay due to non-recurrent, incident related congestion, as well as lower the chance of secondary crashes. While much work has been done in the direction of identifying the benefits stemming from the delay savings by freeway patrols, little has been done to identify the potential savings from lowering the likelihood of secondary crash occurrence. Using a 5-year incident data base from the Borman Expressway, we develop logistic regression models to examine what primary crash characteristics are likely to influence the likelihood of a secondary crash. The findings suggest that clearance time, season, type of vehicle involved, and lateral location of the primary crash significantly influence the likelihood of secondary crash occurrence. Further, the 1995 potential benefit from secondary crash reduction was $568,080 exceeding the 1995 Hoosier Helper freeway service patrol program costs by a factor of 1.38. Given a better understanding of what contributes to secondary crash occurrence, various components of incident management can be operated at a higher level of cost-effectiveness.

Freeway Service Patrols: A State of the Practice

Freeway service patrols have been cited as one of the most effective elements of an incident management program for reducing incident detection time and incident duration. Service patrol programs utilize roving vehicles to patrol congested and high incident sections of urban freeways. The state of the practice of freeway service patrol programs in the United States is documented in this paper. A telephone survey was conducted with managers of 53 freeway service patrols in 22 states. Approximately 74 percent of the surveyed service patrols are sponsored exclusively by public agencies. Approximately 47 percent of the surveyed patrols are sponsored exclusively by Department of Transportations; 6 percent are sponsored exclusively by police agencies; and 21 percent are sponsored by multiple public agencies. Approximately 34 percent of the patrols receive federal support funding. Finally, 27 percent of the patrols operate with private funding sources. Service patrol hours of operation vary from program to program, with the most common being coverage of the weekday a.m. and p.m. peak periods. Approximately 70 percent of the surveyed agencies own and operate their own vehicles, whereas 26 percent contract with private tow companies to provide drivers and vehicles. Benefits associated with service patrols are typically quantified by multiplying a value of time by the estimated delay reduction provided by the service patrol in vehicle-hours. Available benefit to cost analyses for 15 of the service patrols studied ranged from 2:1 to 36.2:1. A contact list and recommendations for agencies interested in starting a new service patrol program are also included in this paper.

Investigation of Freeway Incident Characteristics and Their Influence in Planning an Incident Management Program

Nonrecurrent congestion caused by highway incidents is a major concern for transportation agencies and millions of road users in most metropolitan areas in the United States. Incidents account for 60 percent of congestion-induced delay. As a low-cost approach to incident management, freeway service patrol programs have gained wide popularity. However, information on freeway incident characteristics is limited. In the current paper, incident data recorded by the Hoosier Helper program in north-west Indiana is analyzed. The distributions of incident frequency and clearance time by incident type and lateral location are reported. The variation of incident rate with time of the day is examined, and the influence of various factors affecting the frequency and clearance time of incidents is explored. Recommendations are made to improve the freeway service patrol program, based on the incident data analyzed. The information provided in this study may be useful for planning similar patrol programs in other metropolitan areas in Indiana and other states.

New Model for Predicting Freeway Incidents and Incident Delays

This paper presents a new model that predicts the number of freeway incidents and associated delays based on general freeway segment characteristics, traffic volumes, and incident management procedures. The model is intended to be used in planning capacity-enhancing freeway improvements and incident management programs. Estimates of incident frequencies, severity, durations, and delays are provided for seven standard incident types, each of which represents a significant fraction of total unplanned incidents and has severity and/or duration characteristics substantially different from the others. In addition to describing the incident prediction model, the paper addresses the need for a coordinated national strategy for collecting incident data, with particular attention to urban freeways. It concludes that the incident data systems that have evolved in several urban areas, often in connection with freeway service patrols and incident response team activities, already provide a valuable nationwide data resource for understanding incident patterns and their variations. However, better national coordination of locally collected incident data would be helpful for addressing issues beyond the scope of the local concerns for which virtually all current systems were originally designed. Specific areas for improvement include the definitions of incident types, descriptions of incident locations (relative to both the length and breadth of the highway), and data recording the critical times during incidents such as when detection, response, and clearing occur. Language: en

I-880 Field Experiment: Analysis of Incident Data

The I-880 field experiment has produced one of the largest data bases on incidents and freeway traffic-flow characteristics ever compiled. Field data on incidents were collected through observations of probe-vehicle drivers before and after the implementation of freeway service patrols (FSPs) over a freeway section. Supplementary information was collected from the California Highway Patrol’s computer-aided dispatch system, FSPs, and tow-truck company logs. The incident patterns are described and the major factors affecting incident frequency and duration are identified. FSPs significantly reduced the response times but did not have a significant effect on the duration of all incidents.