Methodology for Identifying Highway Safety Problem Areas

Abstract

Safety programs can provide benefits only if they apply effective countermeasures to the locations and areas that really need safety treatment. A methodology of areawide safety analyses is presented to detect these areas (states, counties, townships, etc.) that should be considered for safety treatment. The method is implemented for Indiana at the county level. The method uses regression models to estimate the normal number of crashes in individual counties. The above-norm numbers of crashes calculated for several past years are used to predict the above-norm value for the future year when the safety treatment is to be applied. The counties are priority ranked using the combined criterion including both the above-norm number of crashes and the confidence level. Above-norm crashes represent the magnitude of the problem—specifically, how many crashes could be avoided if the safety level was normal. A confidence level represents the chance that the observed excessive number of crashes is not just a random effect, but indicates a real safety problem. The example analysis is performed for the alcohol-related crashes to illustrate and test the method. The results are promising and in conformance with the results obtained in the previous study.