Public Roads: A Journal of Highway Research, Vol. 36. No. 10

Viner, J.G.; Hosea, Harold R.; Whyte, Adrienne A. · 1971 · ROSA P / United States. Government Printing Office

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Summary

This document comprises two primary articles from the October 1971 issue of *Public Roads*, a journal of highway research published by the Federal Highway Administration (FHWA). The first article, "Experience to Date with Impact Attenuators" by John G. Viner, addresses the critical safety problem of collisions with fixed roadside objects, which constitute the leading cause of fatalities on Interstate highways. The second article, "Fatal Accidents on Completed Sections of the Interstate Highway System, 1968-70" by Harold R. Hosea, analyzes trends in fatal accident data to identify changes in accident patterns over a three-year period. Viner’s study evaluates the performance of experimental impact attenuators, also known as crash cushions, installed at elevated exit ramps and gores. The research relies on a national experimental evaluation program involving 38 states, analyzing 129 recorded accidents and various full-scale crash tests. The FHWA established specific performance criteria for these devices, including a vehicle weight range of 2,000 to 4,500 pounds, an impact speed of 60 mph, and a maximum average deceleration of 12 g’s. The study found that these barriers significantly reduced fatalities and hospitalizing injuries. Analysis of 129 accidents indicated that without the attenuators, 30 incidents would likely have resulted in hospitalizing injuries or fatalities, whereas only three hospitalizing injuries and one fatality actually occurred. Specific devices, such as steel-drum barriers, Fitch Inertial barriers, Hi-dro cushions, and TOR-SHOK units, were evaluated. While head-on impacts were generally well-managed, with average decelerations often between 3 and 9 g’s, oblique impacts sometimes resulted in vehicle "pocketing" or contact with rigid backup walls. Based on this evidence, the FHWA declared steel-drum, Hi-dro, sand container, and TOR-SHOK devices as operational rather than experimental, though it noted that side-hit characteristics required further improvement. Hosea’s analysis of 9,086 fatal accidents between 1968 and 1970 reveals that two-thirds of fatal accidents involved only one moving vehicle. The most common single-vehicle accident type, running off the road, decreased slightly in relative importance, while pedestrian fatalities rose from 11.6% to 12.6% of single-vehicle accidents. Among multiple-vehicle accidents, head-on collisions increased from 33.0% to 38.2% of the total, driven largely by out-of-control vehicles from opposing lanes rather than wrong-way drivers. The study also identified temporal patterns, noting that Saturday was the peak day for accidents and that the highest proportion of crashes occurred between 1:00 a.m. and 2:00 a.m. Weather conditions remained consistent, with 80% of crashes occurring in clear or cloudy weather, though 35% of head-on collisions caused by out-of-control vehicles occurred on wet pavements. The significance of these findings lies in the validation of impact attenuators as effective safety hardware, leading to their inclusion in Federal-aid highway projects. The data confirms that while Interstate systems have lower fatality rates than conventional highways, fixed-object collisions remain a primary hazard. The research underscores the need for continued development of barrier designs to improve performance in oblique impacts and highlights specific high-risk periods and accident types for targeted safety interventions.

Key finding

Impact attenuators significantly reduced fatalities and hospitalizing injuries at fixed roadside obstacles, with most collisions resulting in deceleration levels between 4 and 9 g's.

Methodology

dataset

Sample size: 129

Provenance

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

Topics

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• incidence prevalence
• roadway lighting effects
• rail grade crossings
• crash typology
• perceptual countermeasures
• naturalistic crash near crash

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).

• Empirical Findings: crash risk outcomes, observational prevalence
• Methodological Resource: dataset resource