A safety engineering study at the general motors proving ground revealed that off-the-road accidents were the most prevalent type and concluded that this was the greatest potential hazard in the operation. Comparison with accident statistics and the physical characteristics of roadsides on public highways leads to the same conclusions. Between 30 and 35 percent of highway fatalities occur in off-the-road accidents, year after year. An objective look at many public highway roadsides shows that they offer few safeguards in the event of vehicle malfunction or human malfunction and in the eyes of the industrial safety engineer, much of the roadside is deficient in this respect. The objective of this study is to develop criteria for roadside design which would remove these deficiencies. The severity of operation through roadside and median ditches as a function of speed and cross-section detail is measured in terms of accelerations along the principal axes as a test car is driven through the ditch. Measured values are correlated with severity as gauged by the driver. Cross-section design criteria are developed such that the severity of accidents at legal road speeds can be kept within the tolerable range. Guardrails are recognized as a feature which must be resorted to on occasions, and thus must be considered as a part of roadside design. Full-scale test results of guardrail installations, emphasizing modified end treatments, are given. The hazards of striking standard traffic signs and light poles are indicated and practical solutions are suggested. Analysis and measurement of ground surface reaction coefficient relates passenger car stability factors to roadside slope values such that criteria can be developed for significant design factors. The comparative costs of roadsides designed for safety are developed for specific examples of roads passing through both level and wooded hilly terrain. (Author/Publisher) j
Samenvatting