Modeling of the Impact of Geometric Design, Topography and Road Access in Rural Road Accidents by Factor Analysis and Generalized Linear Regression (Case Study: Ways of Kerman Province)

The purpose of this study is modeling the effects of geometric factors geometric design variables such as characteristics of horizontal and vertical curve, longitudinal slope of road and environmental conditions like as land uses which are around the road according to region types (residential area, farms), types of topography (flat, rolling, mountain), kinds of access (protected or not), and access number (U-turn and access to subsidiary), simultaneously. The data are gathered by using plan, longitudinal profile, and access maps around the four accident-prone axes in the pieces with a length of 5 km.in Kerman province, where is the largest province in Iran and has the third highest stage at the number of road accidents. After correlation analysis, linear regression, generalized linear regression, Poisson and negative binomial models are fitted on information and finally, the most appropriate models are identified. Finally, Poisson generalized linear model with more fitting index and less percent relative error than the linear regression has been chosen. In Poisson generalized linear model, Characteristics of vertical curves factor with variables such as (number of vertical curves, average slope difference of vertical curves and, average difference of total slope) and the type of topography with variables like (mountains Existence, average Longitudinal of land slope and hill region due to the average slope) have played a major part as the most effective variables in increasing the number of accidents. Also, access variables including (the number of access and U-turn, the number of unprotected access and, the existence of residential area) have had correlate with the number of accidents. Reduction of slope difference between axes in curves, correct design for vertical curves and, avoiding large longitudinal slope could be an effective step in reducing the number of accidents, in road design for mountainous topography in the future.