Driver Awareness of Highway Sites With High Skid Accident Potential

Hanscom, Fred R. · 1974 · ROSA P / United States. Federal Highway Administration

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Summary

This 1974 study by Fred R. Hanscom, conducted for the Federal Highway Administration, addresses the critical gap in skid accident prevention research: the driver’s role. While previous research focused heavily on tire-pavement interactions and engineering solutions like skid-resistant surfaces, this study investigates whether warning signs can effectively induce driver awareness and safe behavioral responses at high-risk locations. The research specifically targets two hazards: wet pavements subjected to high frictional demands on curves and bridges prone to preferential icing. The study also considers the political and liability implications of using warning signs, noting that some agencies resisted signs containing the word "slippery." The experimental design involved field studies at five sites: three curved highway sections for wet pavement conditions and two bridge approaches for icy conditions. At the curve sites, researchers tested five experimental signing conditions, ranging from a standard "Slippery When Wet" sign to more conspicuous versions featuring flashing lights and advisory speed limits. Data collection utilized the Traffic Evaluator System to measure vehicle speeds and interviews to assess driver perception. At the bridge sites, researchers compared activated (flashing) and nonactivated signs placed both at the bridge and 1,000 feet in advance, testing during periods of potential icing under both daylight and darkness. Skid resistance was measured using a decelerometer method, chosen for its direct perceptibility to drivers. The results demonstrated that signing effectiveness varied significantly by design and location. For wet pavement curves, only signing conditions incorporating flashing lights successfully reduced the mean speeds of the highest quartile of motorists below the critical safe speed determined by roadway geometry and surface conditions. Standard signs without flashing lights were ineffective. Questionnaire data revealed that while 60% of motorists saw and correctly interpreted conspicuous signs, only about 1% cited the sign as their primary cue for hazard; drivers relied more on roadway curvature, pavement appearance, and other motorists' behavior. For icy bridges, activated signing elicited significant speed reductions at the bridge entry and on the deck. Activated signs placed directly at the bridge had a greater impact than those placed in advance. Drivers were more responsive to signs during periods of greater hazard, and improved results were observed on approaches with short sight distances where the bridge did not visually compete for attention. The study concludes that warning signs can be a cost-effective countermeasure for skid hazards, but their design and placement are critical. Flashing lights are necessary to influence the behavior of faster drivers on wet curves, while activated signs are effective for icy bridges, particularly when placed at the hazard location. The findings highlight that driver awareness is multifaceted, relying on environmental cues beyond signage. The report recommends further research into sign credibility and liability issues, emphasizing that engineering solutions must account for human factors to be effective.

Key finding

Experimental signing conditions incorporating flashing lights were effective at reducing highest quartile mean speeds below the critical safe wet pavement speed, and activated signing significantly reduced speeds on icy bridges with bridge-located signs having a greater impact than advance signs.

Methodology

field_study

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

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• rail grade crossings
• signage environment
• perceptual countermeasures
• road surface friction
• roadway lighting effects