Modeling a Road Safety Composite Index for Two-Way Two-Lane Roads Influenced by Abutting Land Uses

Most crash prediction models in two-way two-lane roads describe the geometric characteristics. This study measures the role of abutting land uses in declining the road safety conditions. The objectives of this study are: (1) Developing a composite index that explains the road safety condition in the road segments running through various land uses; (2) Identifying the land use related roadside hazards that influence the road safety; (3) Determining the share of each land use related factor; and (4) Developing applied methods to enhance roadside safety abutted by land uses. In this study, 74 kilometers of Karaj-Chaloos Road were analyzed using the Data Envelopment Analysis. This method was used to define the resulted efficiency score as a composite index which can best define the safety status in terms of quantitative and qualitative measures. In each segment, the land uses were analyzed in terms of three criteria including the land use density, driveway density, and the roadside hazards utilizing the existing plans and field studies. The measures of these criteria were considered as the imput values of the DEA model. The outputs in the Data Envelopment Analysis model were inversed values of expected crash frequencies which were estimated by compounding the predicted and observed crash frequencies through the Empirical Bayesian methodology. The results by the Data Envelopment Analysis show that the roadside hazards due to abutting land uses would strongly affect the safety indx after which the driveway density and land use density would stand as the second and third factors respectively.