The effects of in-vehicle and infrastructure-based collision warnings at signalized intersections

Inman, Vaughn W.; Davis, Gregory W. · 2009 · ROSA P / Turner-Fairbank Highway Research Center

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Summary

This study, conducted by the Federal Highway Administration, investigates the effectiveness of Intelligent Transportation System (ITS) countermeasures designed to prevent straight crossing-path crashes caused by red light violations. Motivated by the high incidence of fatalities and injuries from such collisions, the research evaluates whether warning potential victims of an imminent threat can significantly reduce crash risk. The study specifically examines three warning modalities: an infrastructure-based warning (immediate red signal with flashing wig-wag lights), an in-vehicle warning (dashboard light, voice annunciation, and brake pulse), and a simultaneous combination of both. Additionally, the research assesses whether the presence of leading or following vehicles influences driver response to these warnings. The experiment utilized a high-fidelity driving simulator with 191 licensed participants. Researchers employed a modified method of limits to determine each driver’s individual decision point for stopping at an amber signal. Warnings were then triggered at a time-to-stop-line where the probability of a driver stopping for a standard amber signal was less than 10 percent, ensuring that any delay in arrival was attributable to the warning rather than normal signal response. Participants were exposed to one of three traffic conditions: driving alone, following a vehicle closely, or being closely followed. The primary metric for effectiveness was whether the warning delayed the driver’s arrival at the intersection stop line by at least one second, which would theoretically provide sufficient clearance to avoid a collision with a violator traveling at 45 mph. The results demonstrated that all three warning types were effective in delaying drivers. The simultaneous activation of both infrastructure-based and in-vehicle warnings was the most effective, delaying 95 percent of drivers by at least one second. The in-vehicle-only warning delayed 80 percent of drivers, while the infrastructure-only warning delayed 67 percent. The study found no detectable effect of car-following conditions on the probability of stopping; the presence of leading or following vehicles did not significantly alter driver response rates to the warnings. Response time analyses indicated that drivers reacted quickly to the warnings, with the combined warning eliciting the fastest accelerator release and brake press latencies. The findings suggest that integrated warning systems combining both infrastructure and in-vehicle alerts offer the highest potential for reducing red light running collisions. The significant effectiveness of the combined warning implies that redundancy in alert modalities enhances driver compliance and reaction speed. Furthermore, the lack of influence from surrounding traffic suggests that these warnings remain effective regardless of immediate traffic context. These results support the deployment of Cooperative Intersection Collision Avoidance Systems (CICAS) that utilize multi-modal alerts to protect potential victims of red light violators, potentially contributing to substantial reductions in intersection crash severity and frequency.

Key finding

The simultaneous infrastructure-based and in-vehicle warning delayed 95 percent of drivers, compared to 80 percent for the in-vehicle only warning and 67 percent for the infrastructure-based only warning.

Methodology

simulator

Sample size: 191

Provenance

The full processing record for this entry. Every stage of this paper's journey through the pipeline is logged — what ran, with which tool and model, how many attempts it took, and when it last completed. Discovered via bulk_ingest_rosap on 2026-05-23 (6 acquisition events logged).

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

Topics

Ranked by relevance to this paper. Hover a topic for its definition.

• auditory warnings
• time to collision looming
• braking response
• rail grade crossings
• perceptual countermeasures
• vru facing ehmi

Information type

What kind of knowledge this paper contributes, grouped by family — independent of topic (what it is about) and method (how it was studied).

• Applied Guidance: countermeasure evaluation
• Empirical Findings: behavioral performance data