Enhancing Transportation: Connecting TSMO and Safety
U.S. Department of Transportation
The safe and efficient movement of people and goods is one of the most basic missions of any transportation agency. More and more, transportation agencies are realizing the importance of TSMO to help them achieve their safety-focused mission.
TSMO strategies can help reduce injuries and fatalities on our roadways and support The Road to Zero vision.1 Significant overlap exists between strategies that improve operations and those that improve safety, including access management strategies, signal optimization, winter weather operations, traveler information, and traffic incident management. Safety strategies can have positive impacts on operations, and operational strategies can result in improved safety of the transportation network. Below are examples of TSMO strategies that have safety benefits:
TSMO and safety are inherently linked. For example, congestion is a frequently cited reason drivers give for aggressive driving.3 By helping to reduce congestion, TSMO strategies can reduce unsafe driver behaviors. In 2018, the Texas Department of Transportation (DOT) renamed its Traffic Operations Division, where both TSMO and safety are housed, to the Traffic Safety Division. At the Washington State DOT, safety is part of its TSMO program.
Safety engineers should be part of the planning and implementation of TSMO strategies to ensure that the safety impacts of TSMO are considered. Although TSMO offers many safety benefits, in some instances improving mobility, and thus travel speeds, can increase safety risks. Likewise, specific safety treatments can reduce efficient mobility. For example, protected-only left turn signal phases are generally safer than permitted or protected/ permitted phasing but typically cause drivers to wait longer at signals. Alternatively, managed lanes often create differences in speed profiles with adjacent general use lanes that may increase safety risks. Using a data-driven, performance-based approach for both safety and TSMO planning will help agencies better understand the potential impacts of safety and TSMO strategies and identify the appropriate threshold for risk. Making these tradeoffs involves balancing the needs of different users of the system based on community goals and priorities.
A lack of information exists as to the safety impacts or crash modification factors associated with many TSMO strategies. The American Association of State Highway and Transportation Officials (AASHTO) Highway Safety Manual has limited information to help predict the safety performance of TSMO strategies. Ongoing research by the Federal Highway Administration (FHWA) and the National Cooperative Highway Research Program aims to address many of the knowledge gaps and support agencies in making important safety and mobility decisions. For example, the FHWA has developed the Intersection Control Evaluation, a data-driven, performance-based framework and approach. It supports agencies in evaluating their intersection configuration and control options. It also helps them to balance their operational, safety, and multimodal objectives.4
How Has This Worked In Practice?
1 The Road to Zero is a vision for achieving zero roadway deaths by 2050. It is supported by a coalition managed by the National Safety Council and supported by the U.S. Department of Transportation. For more information, see: https://www.nsc.org/road-safety/get-involved/road-to-zero. [ Return to note 1. ]
2 SafeHighways.org, Enhancing Safety Service Patrol Driver's Safety, 2018. Available at http://www.safehighways.org/safe-highway-matters/fallwinter-2013/enhancing-safety-service-patrol-drivers-safety/. [ Return to note 2. ]
3 Stuster, J., Aggressive Driving Enforcement: Evaluations of Two Demonstration Programs, National Highway Traffic Safety Administration, 2004. Available at: https://www.nhtsa.gov/sites/nhtsa.dot.gov/files/809707.pdf. [ Return to note 3. ]
5 FHWA, "Signalized Intersection Safety Strategies," (Washington, DC: February 2008). Available at: https://safety.fhwa.dot.gov/intersection/other_topics/fhwasa08008/sa4_Signal_Coordination.pdf. [ Return to note 5. ]
6 Dutta, N., M. D. Fontaine, R. A. Boateng, and M. Campbell, Evaluation of the Impact of I-66 Active Traffic Management System: Phase II, Final Report Virginia Transportation Research Council (VTRC) 19-R7, October 2018. Available at: http://www.virginiadot.org/vtrc/main/online_reports/pdf/19-R7.pdf. [ Return to note 6. ]
7 U.S. DOT, Intelligent Transportation Systems (ITS) Joint Program Office, Investment Opportunities for Managing Transportation Performance through Technology, January 2009. [ Return to note 7. ]
8 Maryland DOT Coordinated Highway Action Response Team, "CHART Traffic Incident Management." Available at: https://chart.maryland.gov/about/incident_management.asp. [ Return to note 8. ]
9 Oregon DOT, Portland Region 2016 Traffic Performance Report, 2016. Available at: https://www.oregon.gov/ODOT/Regions/Documents/Region1/2016_TPR_FinalReport.pdf. [ Return to note 9. ]
United States Department of Transportation - Federal Highway Administration