Human Factors Issues in Intersection Safety [Issue Briefs vol. 12]

NHTSA · 2009 · ROSA P / United States. Department of Transportation. Federal Highway Administration. Office of Safety

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Summary

This issue brief from the Federal Highway Administration addresses the critical role of human factors in intersection safety, motivated by the finding that driver error contributes to approximately 90 percent of all crashes. While automotive and highway design advancements continue, the driver remains a variable engineers cannot directly control. The document aims to clarify how drivers interact with intersection environments to inform design strategies that mitigate error and save lives. It frames the driving task as comprising control, guidance, and navigation, noting that drivers often shed navigational loads to maintain physical control when information overload occurs. The paper synthesizes existing research and guidelines to analyze driver attention, decision-making, and error patterns. It highlights that humans are serial processors, making the high cognitive load of intersections particularly challenging. Key data points include a 2006 National Highway Traffic Safety Administration study indicating that nearly 80 percent of crashes involved drivers looking away from the roadway prior to conflict, and estimates that drivers engage in distracting secondary tasks nearly 30 percent of the time. The text categorizes specific perceptual failures and errors by intersection type, such as failing to detect signals or lane assignments at signalized intersections, misjudging closure rates at unsignalized intersections, and failing to yield at roundabouts. It also references standard design criteria, such as the AASHTO Green Book, which assumes a "design driver" with alert mental and physical capabilities. The findings emphasize that driver performance is heavily influenced by expectancies and visual characteristics. When drivers encounter unfamiliar or inconsistent designs, such as obscured traffic controls or poor sight distances, response times increase and errors become more likely. The brief identifies specific vulnerabilities, such as older drivers’ diminished ability to judge closure rates during left turns. To address these issues, the paper advocates for design principles of "clarify and simplify" to maintain moderate driver workload. Specific engineering solutions include using advanced guide signs, large pavement markings, improved signal visibility (e.g., larger LED signals), and reducing the "dilemma zone" through advanced detection. Additional recommendations involve removing visual obstructions, optimizing signal placement, and enhancing pedestrian crossings with high-visibility markings and refuge islands. The significance of this work lies in its practical application of human factors principles to reduce the inevitability of driver error. By aligning roadway design with human cognitive and visual limitations, engineers can create environments that reinforce correct driver expectancies and minimize confusion. The brief concludes by pointing to training resources and further reading, underscoring the necessity for transportation professionals to integrate human factors into highway design, operations, and safety decisions to effectively address the complex demands of intersection navigation.

Key finding

Nearly 80 percent of all crashes and 65 percent of all near-crashes involved the driver looking away from the forward roadway just prior to the onset of the conflict.

Methodology

review

Provenance

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

Topics

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• rail grade crossings
• looked but failed to see
• driver vru interaction
• crash reconstruction hf
• perceptual countermeasures
• roadway lighting effects

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: design guidelines
• Empirical Findings: behavioral performance data
• Theoretical Contribution: theory or model