Safety Impacts of Signal System Retiming to Improve Progression

North Carolina Department of Transportation (NCDOT) owns and maintains coordinated traffic signal systems throughout the state in primarily rural and suburban areas. NCDOT’s Signal System Timing and Operations office assists the local Divisions with the signal system retiming program to update traffic signal settings of existing coordinated corridors. This program has primarily focused on identifying locations with the input of Division Engineers and operational summary data to prioritize the corridors updated each year. To date, with the ability of signalized intersections to manage vehicle and multimodal conflicts, the crash rate has been significantly reduced compared to the past. However, as traffic volume continuously increases, drivers who arrive at a signal at the end of the green period are very likely to speed up to proceed to the intersection. This yields crash hotspots at signalized intersections, which could increase if traffic is not able to progress smoothly. According to the Federal Highway Administration (FHWA, 2023), about one-third of crashes occurred at signalized intersections, among which rear-end crashes and right-angle crashes are the most common types. Therefore, minimizing the safety risk at signalized intersections has been an important issue for DOTs to address in the last century, with many potential treatments depending on the issues identified. In recent decades, signal coordination has been utilized as a method to effectively improve the performance of the traffic control system, especially in high density urban areas. It has been widely used as a measure to mitigate congestion, reduce travel time, and eliminate travel delays. On the other hand, however, it may change the traffic flow feature at intersections, which could lead to potential safety issues. As signal coordination has been extensively implemented into urban signalized arterials, safety concerns were unsurprisingly raised by both transportation engineers and the public. Since traffic coordination may result in higher mainline speeds than non-coordinated conditions, most of these opinions came up with the worries that a higher speed may increase the risk of being involved in a traffic crash, particularly injury or fatal crashes. Inversely, improved progression of traffic may reduce the total crash count by reducing rear end collisions that can occur in start-stop traffic. To date, there is neither solid theoretical-level models to analyze this issue, nor solid evidence from the field to support the concern. In this regard, this research effort aims to assess the effects of traffic signal coordination on the safety performance of North Carolina coordinated arterials. The research is anticipated to develop predictive model(s) that can estimate or predict crashes based on the operational or site characteristics of North Carolina signalized corridors.

Language

• English

Project

• Status: Active
• Funding: $242,839.00
• Contract Numbers:

  RP2025-09

• Sponsor Organizations:

  North Carolina Department of Transportation

  Research and Development
  1549 Mail Service Center
  Raleigh, NC  United States  27699-1549
• Managing Organizations:

  North Carolina Department of Transportation

  Research and Development
  1549 Mail Service Center
  Raleigh, NC  United States  27699-1549
• Project Managers:

  Kim, Jay

• Performing Organizations:

  North Carolina State University, Raleigh

  Institute for Transportation Research and Education
  Campus Box 8601
  Raleigh, NC  United States  27695-8601
• Principal Investigators:

  Cunningham, Christopher

• Start Date: 20240801
• Expected Completion Date: 20250731
• Actual Completion Date: 0
• USDOT Program: Transportation, Planning, Research, and Development

Subject/Index Terms

• TRT Terms: Crash rates; Predictive models; Traffic safety; Traffic signal control systems; Traffic signal timing
• Geographic Terms: North Carolina
• Subject Areas: Highways; Operations and Traffic Management; Planning and Forecasting; Safety and Human Factors;

Filing Info

• Accession Number: 01942884
• Record Type: Research project
• Source Agency: North Carolina Department of Transportation
• Contract Numbers: RP2025-09
• Files: RIP, STATEDOT
• Created Date: Jan 21 2025 10:22AM