The National Academies

NCHRP 03-108 [Active]

Guidance on Quantifying Benefits of TIM Strategies

  Project Data
Funds: $499,985
Staff Responsibility: Mark S. Bush
Research Agency: Noblis, Inc.
Principal Investigator: Vaishali Shah
Effective Date: 7/10/2013
Completion Date: 10/31/2017

Traffic incidents are a major source of congestion. Traffic incident management (TIM) consists of “a planned and coordinated multi-disciplinary process to detect, respond to, and clear traffic incidents so that traffic flow may be restored as safely and quickly as possible. Effective TIM reduces the duration and impacts of traffic incidents and improves the safety of motorists, crash victims, and emergency responders.”  (FHWA Traffic Incident Management Website)  The National Traffic Incident Management Coalition (NTIMC) has adopted the National Unified Goal (NUG) for TIM to “achieve enhanced responder safety; safe, quick traffic incident clearance; and more prompt, reliable, interoperable communications.” About half of congestion is caused by temporary disruptions that take away part of the roadway from use, or "non-recurring" congestion. The three main causes of non-recurring congestion are: incidents ranging from a flat tire to an overturned hazardous material truck (25 percent of congestion), work zones (10 percent of congestion), and weather (15 percent of congestion). Non-recurring events dramatically reduce the available capacity and reliability of the entire transportation system. TIM has received increased attention in recent years as agencies, including transportation and emergency responders, have deployed more personnel and financial resources in this area to improve road user and worker/responder safety, improve mobility and reliability, reduce green-house emissions, and mitigate other environmental impacts. TIM related analytical procedures (for estimation of impacts, benefit/cost of program/strategies, resource allocation, etc.) have made rapid progress, and many agencies have developed their own methods/tools to support improved decisionmaking. Also, the Federal Highway Administration (FHWA), with the help of 11 focus states, has identified three incident specific performance measures for data collection and analysis, i.e., roadway clearance time, incident clearance time, and secondary incidents. However, there are inconsistencies in TIM related estimation methods, and guidance is needed on what should be considered reasonable for accurate TIM program assessment and operations performance measurement under data rich and poor scenarios. In the absence of such guidance, it is very difficult to accurately determine and/or compute economic benefits of these programs and TIM strategies and the use of this information in various evaluations and decision support systems. This is also important to have a better understanding of the scope of the problem and preparing a consistent message related to impacts and benefits that can also be used in training.
The objective of this research is to develop a guidance document for analyzing and quantifying the impacts of traffic incidents and the economic benefits of TIM strategies. The guidance shall be useful and applicable for TIM program mid-level managers/analysts in planning and operations for a broad spectrum of transportation and incident responding agencies with varying TIM program maturity levels and a variety of data collection capabilities.
The guidance document should include:
  1. Methodologies for quantifying impacts of traffic incidents and benefits of TIM strategies. 
    Note: This includes scenarios in both data rich and poor environments. The  methodologies should address relevant cost factors.
  2. Demonstrative applications of the methodologies developed.
  3. Validation of commonly used and/or developed new TIM statistics for framing consistent messages.
  4. Incident (type and severity) related capacity reduction estimates for different roadway types.
The guidance should provide analysis methodologies addressing:
  1. Traffic incidents and congestion;
  2. Secondary incidents; and
  3. Capacity reductions due to incidents in a simple and consistent manner that is credible.
Further, the guidance should enable:
  1. Accurate assessment of an agency’s TIM strategies and communication of results to decisionmakers.
  2. Quantification of impacts and benefits that can be used in developing operational performance measures.
  3. Consideration of quantitative factors such as: safety, mobility, reliability, emissions, business, and freight impacts.
  4. Understanding the relationships between elements, such as roadway type, primary and secondary incidents, level of congestion, capacity reductions due to incidents, etc.
  5. Analytical estimation of secondary incidents based on factors such as incident location, duration, severity, traffic flow, and congestion. 
The Highway Capacity Manual 2010 (HCM 2010) includes capacity reduction estimates due to lane blockages on freeways. There is a need for this information to also be validated with new data considering various road and traffic conditions. Also, there is a need for determining reduction in capacity estimates for other types of roadways to improve accuracy and application of TIM related analytical procedures.
STATUS: Completed - To be published as an NCHRP research report.

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