EVALUATION OF SAFETY ALTERNATIVES BY BENEFIT COST ANALYSIS

There is an increasing awareness of the need to use limited highway safety funds on projects that offer the greatest benefits. This paper describes the development and application of a benefit/cost (B/C) methodology to evaluate roadside safety alternatives. A key part of the methodology is an encroachment-probability model used to estimate the number of accidents expected to occur on a given roadway during a given period of time. Background information and input data for the model are discussed. Some of the topics addressed include encroachment characteristics and traffic speed, density, and vehicle size distributions. Another key element in the methodology is the estimation of accident severity. To achieve this, use is made of impact angle-speed probabilities.