Relationship of Accident Rates and Road Geometric Design

Abstract

Road safety issue has become a major concern worldwide due to the serious consequences of road accidents on countries socio-economics and human lives. The main aim of this paper is to discuss and review the effects of geometric design elements on road accidents including statistical models used over the years and to compare the outcomes of the studies conducted in several countries. A way to improve road safety is improving road geometric design to mitigate accidents occurrence and severity on roadways. In order to improve the road design, it is crucial to evaluate and define the relationship between road geometric design elements and road accidents. Studies have tried to relate road geometric design elements such as lane number, sight distance, super-elevation, median width and type, lane and shoulder width, curve radius, gradient, and horizontal and vertical alignments to accident rates. Due to the interrelations between geometric design elements with each other and with other road accident factors, and also lack of reliable methodology of relationship estimation between road geometric design and safety. Ongoing enhancement of statistical methods has resulted in many road design-accidents analysis models which have been developed using a variety of statistical modelling approaches such as linear regression models, multiple linear regression models, Poisson regression models, Poisson-Gamma models, negative binomial models, bivariate and multivariate models, generalized estimation regression models, random parameters models, etc. However, some limitations have been encountered using the mentioned statistical models, thereby there are opportunities for road safety researchers to overcome the limitation challenges.