Freeway Management and Operations Handbook
Chapter 10 – Traffic Incident Management
A traffic incident is a non-recurring event that causes a reduction of roadway capacity or an abnormal increase in demand. In most metropolitan areas, traffic incident-related delay (not including other non-recurring delay caused by weather, work zones, etc.) is estimated to account for between 25 and 30 percent of total congestion delay. In smaller urban areas, it can account for an even larger proportion (Reference 1). Although the problems most often associated with traffic incidents are congestion and associated traveler delay, increased fuel consumption, and reduced air quality, the most serious problem is the occurrence of secondary crashes. Another related issue is the danger posed by traffic incidents to response personnel serving the public at the scene.
Although traffic incidents constitute only a portion of all public safety and emergency management incidents, the general principles for effective management of all types of incidents are comparable. Effective traffic incident management (TIM) programs, like other incident management programs, feature ongoing, actively administered, organizationally structured, interjurisdictional, multi-disciplinary and fully documented procedures. More than merely an assemblage of technologies and activities, successful TIM programs must be fully integrated into the culture of the stakeholder institutions.
For example, the Washington state program features high level institutional coordination documented in the Joint Operations Policy Statement (JOPS). This was signed on February 13, 2002, by the Washington State Patrol and the Washington State DOT, and makes a matter of policy the extensive coordination between the two agencies on a number of matters, including traffic incident response. One of the stated goals is the clearance of all incidents within 90 minutes.
Traffic incident management is the systematic, planned, and coordinated use of human, institutional, mechanical, and technical resources to reduce the duration and impact of traffic incidents, and improve the safety of motorists, crash victims, and traffic incident responders. Effectively using these resources can also increase the operating efficiency, safety, and mobility of the highway. This results from reducing the time to detect and verify a traffic incident occurrence; implementing the appropriate response; safely clearing the incident; and managing the affected flow until full capacity is restored (Reference 1).
A traffic incident management program is a logical, structured, and integrated set of traffic incident management activities tailored to a specific geographic area. It includes policies, strategies, and technologies integrated into a multi-agency, multi-jurisdictional environment aimed at reducing the occurrence and impact of traffic incidents. To be successful, a TIM program must be on-going and actively managed. The TIM program should be developed and managed in conjunction with the area's freeway management and operations program. The organization of the TIM program and the operational responsibilities of its participants should fit into the organization structure of the region, recognizing the existing assignment of traffic incident management activities and addressing gaps and overlaps in those assignments.
10.1.1 Purpose of Chapter
The Traffic Incident Management Handbook (Reference 1) treats traffic incident management in depth and is considered the primary reference on the subject. This chapter summarizes that reference, highlighting the essential elements of an effective traffic incident management program. References 2, 3, 4 and 11 should also be consulted.
10.1.2 Relationship to Other Freeway Management Activities
Traffic incident management is often a major element – if not the cornerstone – of a freeway management and operations program. The ultimate success of a traffic incident management program depends on the on-going collaboration and coordination (as discussed in Chapter 2) among the various entities involved. Several ITS components can support and enhance a traffic incident management program, including surveillance (Chapter 15) to detect and verify incidents, disseminating information to travelers regarding the resulting congestion and alternatives (Chapter 13), improving response via the coordination afforded by a Traffic Operations Center (Chapter 14), as well as the real-time sharing of information (Chapter 16) among the affected agencies. Additionally, the various activities and coordination needs for traffic incident management parallel those associated with special event management (Chapter 11) and emergency / evacuation management (Chapter 12).
Traffic incident management is a critically important piece of a freeway management program, and should be considered in all stages of developing and implementing a freeway management and operations program (Chapter 3). Moreover, like all programs and activities that are intended to improve the operation of the transportation network, the performance of a traffic incident management program should be regularly monitored and assessed (Chapter 4), potentially resulting in changes and refinements.
A traffic incident is a non-recurring event on or near the roadway that causes a reduction of roadway capacity or an abnormal increase in demand. Such events include traffic crashes, disabled vehicles, spilled cargo, and highway maintenance and reconstruction projects. Non-emergency events (e.g. ball games, concerts, festivals) are considered planned special events and are discussed in Chapter 11 (Planned Special Event Management) and Reference 6. Emergencies such as natural disasters and terrorist attacks are also unplanned; and they can cause a reduction of capacity or an abnormal increase in demand. But their impacts and management requirements extend well beyond the roadway as discussed in Chapter 12, Freeway Management During Emergencies and Evacuations.
Traffic incidents, such as crashes, spills, and vehicle disablements, vary widely in scope and severity. To mitigate these nonrecurring events in the safest, quickest, and most cost-effective manner requires:
Quick clearance policies and freeway service patrols target minor traffic incident occurrences (Reference 5) but more recently have been applied to aggressive removal of heavily damaged vehicles and cargo (shoving, dragging, scooping, bulldozing), prohibitions against in-lane off-loading of cargoes, towing and recovery practices, and crash investigations. Major incidents like a severe crash or spill (especially hazmat) require a more intensive traffic incident management effort usually involving a cooperative, multi-agency approach. In essence, the unpredictable and dynamic nature of traffic incidents mandates the planning and coordination of a wide range of traffic incident management tools.
The goal of the Traffic Incident Management Handbook (Reference 1) is to assist agencies responsible for traffic incident management activities on public roadways to improve their programs and operations. Agencies typically responding to highway incidents include:
The intended audience for this chapter and the Traffic Incident Management Handbook is primarily managers who are responsible for traffic incident management program development; and field practitioners who are responsible for providing program services on a day-to-day basis. As such, the Traffic Incident Management Handbook provides guidance from two perspectives – first, as a process to follow in establishing a new traffic incident management program or in improving an existing one; and second, through the identification of tools and strategies that can enhance field operations.
Reduced traffic incident duration has proven the greatest contributor to the benefits of a traffic incident management program. Reductions in duration can be achieved by:
Benefits of an effective program are both quantitative and qualitative. The quantitative benefits include:
Qualitative benefits include: enhanced traveler information services, increased driver warning capabilities, improved coordination and cooperation of response agencies, improved public perception of agency operations, and reduced driver frustration.
10.2.3 Key Considerations During Freeway Management Program Development
The Traffic Incident Management Handbook (Reference 1) defines an 8-step process for implementing a successful traffic incident management program. This process, summarized below, contains many of the key elements for establishing a freeway management program as discussed in Chapter 3.
A Traffic Incident Management program needs to be facilitated (but not owned) by a lead agency that can provide staff and resources to do so. The program itself must be multi-agency and multi-disciplinary and must continuously, actively and professionally engage all public and private sector program partners.
Regardless of what process is used for developing a traffic incident management program, it is essential that traffic incident management be coordinated with all other elements of the broader freeway management program, and that overall performance of the transportation network be considered.
In addition to securing broad stakeholder participation from the relevant agencies and jurisdictions, it is also important to ensure that an adequate amount and the appropriate type of public outreach are pursued. Public outreach serves two primary functions: to make the public aware of the value of incident management, leading to generalized public support; and to help the public better understand how their actions, such as moving drivable vehicles out of traffic, and providing good information in reporting incidents, can support effective incident management (1).
10.2.3.1 Traffic Incident Management Program Framework
Reference 3 presents a framework for developing traffic incident management programs as summarized in Figure 10-1. This process includes the previously defined steps but adds additional focus on stakeholder involvement.
10.2.3.2 Traffic Incident Management Self-Assessment
With respect to the next-to-last step identified in Reference 1 (i.e. "reevaluate alternatives"), FHWA has developed a self-assessment tool to assist in this reevaluation process. The Traffic Incident Management (TIM) Self-Assessment tool (Reference 8) is designed to:
The TIM Self-Assessment is a tool to be used by state and regional program managers to assess their achievement of a successful multi-agency program to manage traffic incidents effectively and safely. The tool also provides a method to assess gaps and needs in existing multi-agency regional and statewide efforts to mitigate congestion caused by traffic incidents. The TIM self-assessment is not intended as a one-time exercise, but should be conducted on an annual or biennial basis. This will provide a consistent measure of program improvements and allow for continual refocusing of resources to those areas needing them most.
The TIM Self-Assessment consists of a series of questions (summarized in Table 10-1) designed to allow those with traffic incident management responsibilities to rate their performance in specific organizational and procedural categories – specifically, Program and Institutional Issues, On-Scene Operations Issues, and Communications and Technology Issues. The questions in each of these areas address the essence of good traffic incident management programs based upon more than ten years of knowledge and experience gained nationwide. Each question is scored from 0 (no progress in this area) to 4 (outstanding efforts).
10.2.4 Relationship to National ITS Architecture
The traffic incident management market package, as defined in the National ITS Architecture (Reference 7), treats both unexpected incidents and planned events so that the impact to the transportation network and traveler safety is minimized. The market package includes traffic incident detection capabilities through roadside surveillance devices (e.g. CCTV) and through regional coordination with other traffic management, maintenance and construction management and public safety and emergency management centers as well as weather service entities and event promoters. Information from these diverse sources are collected and correlated by this market package to detect and verify incidents and implement an appropriate response.
This market package also supports traffic operations personnel in developing an appropriate response in coordination with public safety and emergency management, maintenance and construction management, and other incident response personnel to confirmed traffic incidents. Incident response also includes presentation of information to affected travelers using the Traffic Information Dissemination market package and dissemination of traffic incident information to travelers through the Broadcast Traveler Information or Interactive Traveler Information market packages. The roadside equipment used to detect and verify incidents also allows the operator to monitor traffic incident status as the response unfolds. The coordination with public safety and emergency management agencies might be through data sharing and integration of public safety CAD and transportation management data and communication systems or through other communication with emergency field personnel.
10.2.5 Technologies and Strategies
Traffic incident management consists of the following major stages as illustrated in Figure 10-2:
A wide variety of techniques and approaches can be applied to each of these stages. These are summarized below with further detail found in Reference 1.
Detection is determining that a traffic incident has occurred. Rapid detection is necessary to minimize the period of time during which roadway capacity is reduced. Methods commonly used to detect incidents include:
Verification is determining the precise location and nature of an incident, as well as the display, recording, and communication of this information to the appropriate agencies. Proper verification is required to reduce the time required to deploy an appropriate response to the scene of an incident. Operations center personnel may verify incidents and communicate with incident responders on scene, or provide details to emergency agency dispatchers. Verification methods include:
Motorist information is the activation of a variety of communications media to relay traffic incident conditions to travelers. Dissemination of motorist information is one of the primary services provided by many TMCs, as discussed in Chapters 13 and 14 herein. Techniques include:
Response is the activation, coordination, and management of the appropriate personnel, equipment, and communication links and motorist information media as soon as it is reasonably certain that a traffic incident has occurred. Timely and effective response reduces the incident's duration, and therefore, the time of roadway operation at reduced capacity. Techniques include:
Site management consists of:
Effective site management increases safety for crash victims, motorists and responders; coordinates responder activities; and decreases the impacts of incidents on the transportation system. Techniques include:
Traffic management is the application of traffic control measures at the incident site and on facilities affected by the traffic incident. Effective traffic management minimizes traffic disruption while maintaining a safe workplace for responders and reducing the likelihood of secondary crashes. Techniques include:
Clearance is the removal of vehicles, wreckage, debris, spilled material and other items from the roadway and the immediate area to restore roadway capacity. Improving traffic incident clearance procedures can:
Refer to Reference 5 for a synthesis of traffic incident clearance policies and strategies.
Recovery consists of restoring traffic flow at the site of the traffic incident; preventing more traffic from flowing into the area and getting trapped in the upstream queue; and preventing congestion from spilling across the roadway network. Thus it encompasses the activities of site management, traffic management and clearance. First responders normally are focused on the immediate vicinity of the traffic incident and likely do not have the resources or information to handle the "big picture." (The end of the queue can range from 1000 feet to 20 miles back from the site.) Resources including traffic operations centers and their operating staff can facilitate recovery by managing the network-wide effects of traffic incidents and thus hastening recovery.
10.2.6 Emerging Trends
The "Freeway Management State-of-the-Practice White Paper" (Reference 9) identifies the following areas as the "state-of-the-art" (Note: Defined in the reference as "innovative and effective practices and the application of leading edge technologies that are ready for deployment in terms of operating accurately and efficiently, but are not fully accepted and deployed by practitioners"):
Reference 11 identifies seven top issues as a roadmap to the future to improve traffic incident management program planning, field operations, and inter-agency communications as follows:
While the specific form and nature of the above techniques and strategies vary from region to region, elements of successful programs have much in common. These implementation and operational elements fall into three major categories – people, practices, and infrastructure as summarized below.
Intelligent Transportation Systems (ITS) – the application of advanced sensor, computer, electronics and communication technologies – complement traffic incident management programs to maximize the efficiency and safety of the transportation infrastructure. ITS can assist in many of the stages of traffic incident management, particularly:
Examples are provided in Reference 1, with two summarized here.
10.4.1 Chicago, Illinois Service Patrol
Chicago's service patrol program, which was kicked off by the Illinois Department of Transportation (IDOT) in 1960, is one of the country's oldest and most successful. The Emergency Traffic Patrol (ETP) initially consisted of several pickup trucks operating during peak periods only. Today, the program, known as Minuteman, has a much broader scope than other service patrols. Whereas most programs focus on removing minor incidents, Minuteman is part of the entire incident response program for IDOT and can clear large truck and cargo spill incidents as well as minor incidents. The program operates around the clock and includes 35 emergency patrol vehicles (the size of a medium-duty tow truck), 11 light utility 4 x 4's, a sand truck, a step van, a tractor / retriever, two 50-ton and two 60-ton heavy-duty recovery units. Every vehicle in the fleet is equipped with heavy-duty push bumpers. One of the country's larger programs, ETP's staff includes 76 positions:
IDOT Minutemen receive comprehensive initial training and frequent ongoing and re-certification training. The patrol operation encompasses 12 beats, which are organized along overlapping shifts and routes to provide extra coverage on high-incident sections. All beats are patrolled 24 hours a day, 365 days a year.
In all, the ETP logs an estimated 1.8 million miles per year. Minutemen typically spend up to 15 to 20 minutes with a motorist at a disabled vehicle. If the disability cannot be corrected, the Minutemen call a motor club or the State Police to order a tow. The Minutemen can transport motorists off the freeway if they so request. Although disabled vehicles are relocated to a shoulder, accident investigation site, or nearby exit, the service patrol does not tow vehicles beyond these points.
A 1990 program evaluation found a benefit-cost ratio of 17:1. Public support for the program is high, as demonstrated by the 900 thank you letters received each year.
10.4.2 Washington State Department of Transportation (WSDOT) Documentation and Evaluation
The Washington State Department of Transportation's (WSDOT) incident response program developed a relational database to organize and store incident records. WSDOT Incident Response Team (IRT) members collect a wide and comprehensive range of data for each incident to which they respond. Data are entered into a portable computer in the field. The data comprising the WSDOT incident response database are identified in Table 10-2.
In 1997, using this database, an independent team of faculty and research engineers evaluated WSDOT's incident management program. The evaluation was based on three measures of effectiveness: (1) congestion mitigation, (2) benefit to cost ratio, and (3) positive public perception. The evaluation revealed substantial benefits associated with the program, including a 12 percent drop in the time required to clear an incident over a two-year period. Another positive finding was a benefit-to-cost estimate in the range of 4:1 to 13:1. The evaluation also pointed out areas for improvement.
1. Federal Highway Administration, Traffic Incident Management Handbook, November 2000, http://ntl.bts.gov/lib/jpodocs/rept_mis/13286.pdf
2. Federal Highway Administration, Incident Management Successful Practices: A Cross-Cutting Study, April 2000. Reports traffic incident management program benefits and lessons learned in addition to summarizing keys to effective traffic incident management training, leadership, and interagency coordination.
3. Federal Highway Administration, Regional Traffic Incident Management Program: An Implementation Guide, May 2001. Documents a framework for establishing and sustaining a traffic incident management program.
4. Transportation Research Board, Special Report 260: Strategic Highway Research: Saving Lives, Reducing Congestion, and Improving Quality of Life, November 2001. Presents the goals and objectives of a research program, funded by and commencing with the next federal-aid highway program authorization, aimed at preventing and reducing the impact of nonrecurring incidents.
5. Transportation Research Board, NCHRP Synthesis Topic 33-05, Safe and Quick Clearance of Traffic Incidents, 2003. This TRB study assesses the state-of-the-practice and identifies successful policies and strategies to effect quick clearance of traffic incidents.
7. U.S. Department of Transportation, Version 4.0 of the National ITS Architecture, http://www.iteris.com/itsarch/