Freeway Service Patrol Research Articles

Evaluating the Impact of Freeway Service Patrol on Incident Clearance Times: A Spatial Transferability Test

Freeway service patrol (FSPs) programs have been considered as an effective tool for traffic incident management in minimizing the adverse effects of traffic incidents. In this study, random parameters hazard-based duration modeling method was used to evaluate the impact of the newly implemented Alabama Service and Assistance Patrol (ASAP) program, using incident clearance time as a performance measure. It was determined that there is a statistically significant difference in the factors that influence incidents clearance times between incidents that occurred inside and outside the ASAP regions. A total of five variables (on-road, nighttime, peak hours, rain, and fire response present) were observed to have random effects along with ten fixed effects variables on incidents occurring inside the ASAP regions. On the other hand, incidents that occurred outside the ASAP regions were found to have three random effects variables (on-road, nighttime, and fire response present) and seven fixed effects variables. The estimation results indicate a significant association of incident clearance times to incident related variables such as involvement of CMVs, fatality, vehicle towing, seat belt indicated as involved, and on-road incidents that occurred both inside and outside the ASAP regions. The results also reveal that incident clearance times are influenced strongly by temporal variables (e.g., nighttime), traffic factors (e.g., AADT), and operational variables (e.g., fire response present) for incidents both inside and outside the ASAP area models. Overall, it was observed that the incident clearance times recorded in the regions where the ASAP program is in effect are significantly different. The findings of this study are expected to be useful for the state traffic incident management (TIM) agencies in developing and executing strategies to minimize incident clearance times. Ultimately, the study provides a data-driven evidence-based assessment of the ASAP program in the state.

Genetic Algorithm for Optimizing Routing Design and Fleet Allocation of Freeway Service Overlapping Patrol

The freeway service patrol problem involves patrol routing design and fleet allocation on freeways that would help transportation agency decision-makers when developing a freeway service patrols program and/or altering existing route coverage and fleet allocation. Based on the actual patrol process, our model presents an overlapping patrol model and addresses patrol routing design and fleet allocation in a single integrated model. The objective is to minimize the overall average incident response time. Two strategies—overlapping patrol and non-overlapping patrol—are compared in our paper. Matrix encoding is applied in the genetic algorithm (GA), and to maintain population diversity and avoid premature convergence, a niche strategy is incorporated into the traditional genetic algorithm. Meanwhile, an elitist strategy is employed to speed up the convergence. Using numerical experiments conducted based on data from the Sioux Falls network, we clearly show that: overlapping patrol strategy is superior to non-overlapping patrol strategy; the GA outperforms the simulated annealing (SA) algorithm; and the computational efficiency can be improved when LINGO software is used to solve the problem of fleet allocation.

Safety of Freeway Service Patrol Operations: Case Study of Florida Road Rangers

Safety service patrols are a proven strategy to mitigate the effects of traffic incidents through quick clearance, incident management, and assistance to other incident responders like police, fire, emergency medical services, and towing. As encountered by other responders, working on or near roadways presents unique hazards for safety service patrol vehicles and operators. Road Rangers are Florida’s branded safety service patrols and, as a mature program with over 100 beats, a suitable case study for safety. This research combined an analysis of Road Ranger traffic crash data for 3 years with a comprehensive safety survey of more than 200 operators to determine safety characteristics related to service patrols. Comparing 200 Road Ranger traffic crashes from 2014 through 2016 with all Florida freeway crashes for the same time period revealed that Road Ranger crashes are five times more likely to involve a parked vehicle, and involve two or more vehicles 95% of the time. Pedestrian involvement, nighttime, shoulder locations, and work zones have higher representation for Road Ranger crashes, but weather is not a factor. Alcohol is three times more likely, drug use five times more likely, and distraction slightly higher when Road Ranger vehicles are struck. A survey of 217 Road Ranger drivers revealed that they are keenly aware of important safety topics like high-visibility safety apparel, non-traffic side vehicle approaches, and the dangers of working where there is limited lateral buffer space. Drivers overwhelmingly believe that they have the training and equipment necessary to do their jobs safely.

Routing design and fleet allocation optimization of freeway service patrol: Improved results using genetic algorithm

Freeway service patrol (FSP), is considered to be an effective method for incident management and can help transportation agency decision-makers alter existing route coverage and fleet allocation. This paper investigates the FSP problem of patrol routing design and fleet allocation, with the objective of minimizing the overall average incident response time. While the simulated annealing (SA) algorithm and its improvements have been applied to solve this problem, they often become trapped in local optimal solution. Moreover, the issue of searching efficiency remains to be further addressed. In this paper, we employ the genetic algorithm (GA) and SA to solve the FSP problem. To maintain population diversity and avoid premature convergence, niche strategy is incorporated into the traditional genetic algorithm. We also employ elitist strategy to speed up the convergence. Numerical experiments have been conducted with the help of the Sioux Falls network. Results show that the GA slightly outperforms the dual-based greedy (DBG) algorithm, the very large-scale neighborhood searching (VLNS) algorithm, the SA algorithm and the scenario algorithm.

Evaluation of the Benefit-to-Cost of Freeway Service Patrol in Advanced Video Surveillance System Environment: A Case Study in China

Abstract With the growing traffic incidents led by the rapid increase of traffic volume on freeways, Chinese government is facing how to ensure the efficiency and safety of the freeway system. One of the hot debates is the efficiency of Freeway service patrols (FSPs) technology in the advanced video surveillance system environment, namely dense video-based surveillance system (DVBSS). To help making a correct decision, this paper develops an effective approach to assess the effectiveness of FSPs in the DVBSS environment. This paper proposes a simulation method to measure the B/C ratios of FSPs in advanced VSS environment. B/C ratios are evaluated under four scenarios namely basic scenario, FSP1, FSP2, and FSP3. All scenarios were simulated in the 9.4-kilometer segment and data were collected from the working log of traffic monitoring center. Among all scenarios, B/C ratio of FSP1 is lowest, sometimes less than1, indicating that not all the FSPs scenarios are effective in the advanced VSS environment. However, the B/C ratios of FSP2 and FSP3 in mean cost scenarios exceed 1, represent as 4.33:1 and 3.47:1 respectively. It indicated that FSPs technology is still an effective way for traffic incident management in VSS environment. To explore the robustness of the results, authors extended the length of patrolling segment to 13.4 kilometers.

Deriving a surrogate safety measure for freeway incidents based on predicted end‐of‐queue properties

Incidents can significantly impact freeway operations and deteriorate mobility and safety. This study quantified their safety impacts through inspecting queue properties. Specifically, the end-of-queue (EOQ), where severe rear-end collisions commonly occur, is employed for safety assessment based on vehicles' trajectories. Since detector data is typically available, this study applied such data for EOQ identification, as opposed to vehicle trajectories that are difficult to collect and process. Three measures related to queue duration, impact area and vehicle number exposed to the EOQ are presented as surrogates. To understand the applicability of these measures, a systematic set of incident scenarios is replicated with VISSIM. Quantitative results are used to estimate regression models, and significant variables are identified. The proposed methods can be used to evaluate safety impact of traffic incident management programs such as freeway service patrol, as well as to determine optimal plans for prearranged incidents such as pothole repair.

Analysis of freeway service patrol with discrete event-based simulation

As an efficient incident management program, freeway service patrol has gained wide popularity. There is increasing need for developing systematic procedures of planning the program to ensure efficient resource allocation and to achieve maximum benefits. A discrete event-based simulation model is developed to replicate the patrol process that includes districting, incident generation, response vehicle dispatching and routing, and incident clearance. Model validation proves its capability to accurately replicate the incident generation/distribution process. Later, the Interstate-95 freeway in south Florida is used as a model application example to test alternatives, and the improved alternative shows better performance compared with the previous even-length districting method and the currently used even-activity districting approach. Besides traditional roving scheme, the simulation model also has the capability to evaluate the prepositioning schemes. Furthermore, sensitivity analysis is performed to examine the impact of operational parameter settings, such as beat districting, incident detection rate, and incident frequency. Although continuous efforts are needed to develop a more comprehensive simulation model for the freeway service patrol program, the application example presented in this study reveals promising application results, and provides an insight into the patrol process as well as a better understanding of the impact of parameters on performance.

The impact of congestion management on air pollution emissions in urban freeways

Urban and semi urban transport contributes considerably to many environmental problems, e.g. air pollution and environmental noise. Congestion in motorways in particular, has a signifi cant effect in traffi c conditions and the atmospheric environment as well. In addition to delays and queues incidents also affect fuel consumption and air pollution. Athens Ring Tollway (“Attiki Odos” or “Attika Tollway” ‐ “AT”) is a 70 km freeway centreline length in each direction and is used as a Ring Road for Athens, the capital of Greece. The harmonious co-existence of the motorway with the environment has been a diffi cult task, but successfully achieved by Attica Tollway regarding environmental noise through the implementation of comprehensive management, including monitoring, assessment & implementation of the appropriate mitigation measures i.e. noise barriers & land use organization. In this article and in order to further calculate and evaluate the benefi ts of AT incident management which is given through Attica Tollway Patrol Service (ATPS), Freeway Service Patrol Evaluation Methodology (FSPE) is used. An FSPE model has been examined for the effect of ATSP in the total length of the freeway for the year 2009.

Evaluating Freeway Service Patrols in Low-Traffic Areas Using Discrete-Event Simulation

Freeway service patrol (FSP) is a low-cost but effective method to identify and clear incidents quickly on freeways, and it has been widely implemented in United States. Most of the related literature focuses on evaluating the reduction of travel delay and secondary collision because of a quicker incident clearance. Although such measures are major concerns in urban areas, they may be of less concern in low-traffic areas. A major function of FSP in low-traffic areas is to assist stalled vehicles, protect stranded drivers, and provide free road assistance services, but its major benefit is to bring direct savings to stranded drivers. This paper presents a new benchmark to evaluate the benefit-cost ratio of FSP in low-traffic areas based on a customized event-driven simulation model. The event-driven simulation model is better than the analytical models and microscopic simulation in this context in that it can accommodate more details than an analytical model while achieve a faster simulating speed than microscopic simulations when the road network is large and the simulation period is long. Lastly, the Safety Assistance for Freeway Emergencies (SAFE) Patrol in Kentucky is evaluated by using the method in this paper to evaluate and estimate the benefit-cost ratios of SAFE Patrol under different scenarios.

Freeway Service Patrol Optimum Operation Policy Based on Queuing Theory

Freeway Service Patrol Optimum Operation Policy Based on Queuing Theory

Evaluating Beat Structure and Truck Allocation for the Tarrant County, Texas, Courtesy Patrol

Nonrecurring congestion poses a significant concern for drivers on urban freeways. Effective incident management relies on many tools to prevent the delays caused by crashes, road debris, and stalled or disabled vehicles. Many urban areas have adopted freeway service patrol (FSP) programs that search the freeway network for incidents, provide aid to motorists, and assist with incident management and clearance. FSP management must consider the patrols' beat structure and the fleet allocation. Both deterministic and probabilistic response time estimates for each beat are used to assess fleet allocations. The goal is to consider whether the urban network should be segmented into as many beats as possible, with individual trucks assigned to each beat, or whether additional trucks should be allocated to fewer beats. The Tarrant County, Texas, Courtesy Patrol (CP) is used as a case study to explore the truck allocation problem with field data. The Tarrant County CP typically uses a one-beat, two-beat, or three-beat configuration with a single truck allocated to each beat. The merits of a two-beat configuration are examined. The study indicates that the incident distribution must be considered during both beat and tour design.

Freeway service patrol deployment planning for incident management and congestion mitigation

This paper investigates the problem of deploying freeway service patrols to detect, respond to and clear traffic incidents in two settings, deterministic and stochastic. The deterministic setting assumes that there is only one scenario of incident occurrence and, in the stochastic counterpart, there are many scenarios, each of which occurs with a probability. The main objective of both problems is to minimize the total incident response time. Rather than minimizing the expected total response time, the stochastic model minimizes the expected total response time over the high-consequence scenarios instead. In both settings, the deployment problem can be formulated as a mixed-integer nonlinear optimization problem, a hard class of problem to solve. To obtain solutions in a reasonable amount of time, three heuristic algorithms are proposed. In particular, one makes use of the dual information, another employs a neighborhood search technique and the third uses simulated annealing, a meta-heuristic algorithm. Numerical experiments based on data from Sioux Falls demonstrate that all three algorithms provide solutions with a significant reduction in total response time without using an excessive amount of CPU time.

Simulation Tool to Assess Impacts of Parameters of Service Patrol Operations

Freeway service patrol (FSP) programs constitute one of the most popular elements of intelligent transportation systems and have been increasingly implemented around the United States. Despite the successes and the benefits of these programs, however, recent budget cuts have increased the need to demonstrate the benefits of the programs, to show the differences in the benefits of different operation schedules, and to select the parameters of the operations to make the best use of available resources. This paper reports on an effort to develop a tool (a) to assess the performance of FSPs under different operation parameters and the impacts of FSP performance on transportation network measures and (b) to select operation parameters. The tool was developed by means of a general purpose simulation modeling environment. The output from the simulation is fed into a spreadsheet that allows assessment of changes in incident durations on transportation network performance in terms of delays, fuel consumption, emission, safety, and dollar values. The applications of the tool indicate that it can be used to assess FSP operation parameters and the systemwide and economic impacts of changing these parameters.

A spatial queuing model for the emergency vehicle districting and location problem

Emergency response systems in urban areas should be located to ensure adequate coverage and rapid response time. We develop a model for locating emergency vehicles on urban networks considering both spatial and temporal demand characteristics such as the probability that a server is not available when required. We also consider that service rates are not identical but may vary among servers and are dependent upon incident characteristics; corresponding districting and dispatching problems are also integrated in the location model. The model is applied using real data for locating freeway service patrol vehicles and results are compared with existing coverage and median models. Results show improvements in the mean response time particularly in cases of high demand for intervention when compared to ‘traditional’ models.

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 intertechnology 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.

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.

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.

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.

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.