Determining the road defects impact on accident severity; based on vehicle situation after accident, an approach of logistic regression

Safety and accident issues are considered as an important problem in the world. Road transportation issues would have a more conspicuous countenance in the country of Iran in which, over 94 percent of all transportations take place through roads. The roads´ contribution to the traffic accidents at mean is 24 percent however this value is 36 percent in Iran. Many parameters, safety signs and equipment, Vertical and horizontal arc combination along the road and all the effective factors in decreasing the accidents, are considered when determining the safety level of the roads. Road defect is being considered as one of the essential factors causing accidents to happen. This article investigates the severity factor of the accident according to the ruined vehicle immovable situation after the accident. The results of this research has shown that most important factors reducing the safety on the suburban roads in Iran is “insufficient road width” pertaining to frequency and “Level difference between road & shoulder” pertaining to accident severity.