The Effect of the Geometric Variables to the Risk of Accidents on Indonesan Toll Roads

Abstract

This paper describes the effect of geometric features on the risk of accidents on the Indonesian toll roads. Variables that were evaluated are: lane width, interior and exterior shoulder widths, median width, bendiness in terms of degrees per kilometre, presence of safety fences and street light, horizontal curve and terrain. The accident prediction models were constructed through homogenous one kilometre length using the negative binomial error structure. Accident risks were derived through the elasticities of each significant variable. It was found that lane width of 3.75 m, interior shoulder width of 0.70 m and exterior shoulder width of 3.00 m are associated with low accident risk for dual-2 toll roads. Lane width of 3.60 m, interior shoulder of 1.50 m and exterior shoulder width of 3.00 m are the best traffic performance for dual-3 toll roads. Safety fences should be provided regardless the median width.