Empirical observations of red light running at arterial signalized intersection.

Zhang, Liping · 2008 · ROSA P / Partners for Advanced Transit and Highways (Calif.)

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Summary

This study investigates the causes of Red Light Running (RLR) at arterial signalized intersections, addressing a critical national safety issue. While previous research established that drivers trapped in the "dilemma zone" (where they cannot safely stop or clear the intersection) are a primary cause of RLR at high-speed intersections, the behavior at lower-speed arterial roads remained less understood. The authors sought to determine whether RLR at these intersections is driven by physical constraints or other behavioral factors, such as inattention or following closely behind other vehicles. To answer this, the researchers conducted an empirical field study at a typical arterial intersection in the San Francisco Bay Area with speed limits of 30–35 mph. Data were collected over one month using nine Autoscope cameras equipped with emulated speed loops at various distances from the stop bar. A probe vehicle with GPS was used to calibrate the sensors, ensuring speed measurement errors remained below 10%. The study analyzed trajectories of three vehicle categories: those running the red light, those stopping at the first yellow signal, and those proceeding through the yellow light. The results revealed that over 90% of RLR incidents were not caused by drivers being trapped in the dilemma zone; instead, these drivers could have stopped safely and comfortably. Specifically, only 3% to 10% of RLR vehicles were within the dilemma zone at the onset of the yellow light. Furthermore, the average speed of RLR vehicles was consistent with the posted speed limits and similar to vehicles legally proceeding through the yellow light. A key finding regarding driver behavior was that over 60% of RLR vehicles had a headway of less than three seconds, indicating they were part of a platoon. The average headway for RLR vehicles was 10% lower than that of vehicles going through the yellow light. These findings suggest that at arterial intersections, RLR is primarily a behavioral issue related to inattention or close following rather than a result of signal timing or speed mismatches. The data indicates that drivers often fail to react to the signal change because they are focused on the vehicle ahead. These empirical observations were utilized to inform the development of an all-red interval extension system for intersection collision avoidance, highlighting the need for countermeasures that address platooning and driver inattention rather than just dilemma zone protection.

Key finding

Over 90% of red light runners at arterial intersections were not trapped in the dilemma zone and could have stopped safely, while over 60% of violations occurred with a headway of less than 3 seconds.

Methodology

field_study

Sample size: 118

Provenance

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Summary generated by qwen3.6-27b-prismaquant on 2026-06-10; verification: verified.

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• rail grade crossings

Information type

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• Empirical Findings: observational prevalence, behavioral performance data