Citation

Glennon JC, Wilton CJ. Transp. Res. Rec. 1976; 601: 51-52.

Copyright

(Copyright © 1976, Transportation Research Board, National Research Council, National Academy of Sciences USA, Publisher SAGE Publishing)

DOI

unavailable

PMID

unavailable

Abstract

The objective of this paper is to enlarge the applicability of a hazard index model developed in earlier research so that it may be used for predicting the effectiveness of roadside safety improvements on all classes of highways. Data was collected for the purpose of estimating roadside encroachment rates, encroachment angle distributions, lateral displacement distributions, and obstacle severity indexes for all classes of highway other than freeways: urban arterial streets, rural two-lane highways, and multilane surface highways. The roadside obstacle severity index in the proportion of total accidents that are either fatal, or nonfatal injury accidents. The major premise is that, as operating speeds increase, the severity index of a particular roadside obstacle increases. A roadside encroachment occurs when a vehicle leaves the traveled way either because of loss of driver control or because of an emergency manoeuver to avoid collision with another vehicle. The parameters that describe the nature of these encroachments are the encroachment rate, distribution of encroachment angles, and distribtuion of lateral displacement of encroaching vehicles. Applying the developed roadside encroachment parameter estimates in the hazard model suggests that relatively little effectiveness can be gained by implementing roadside safety improvements on highways other than freeways.