Development of a Model Considering Effective Factors on the Severity of Freeway Accidents (Case Study of the Tehran- Karaj Freeway)

Although there have been considerable progressions in increasing the safety of the freeway, the importance of freeway accidents and their human and economic costs have made study and modeling of freeway accidents imperative for recognition of the effective factors on their severity. The severity modeling of freeway accidents enables researchers to survey and analyze the effective factors with regards to their severity.In this research, the Tehran – Karaj freeway is used as a case study, and incident information from 1384 to 1387 has been collected from associated organizations. With attention to the nature of driving accidents, many different parameters are effective in causing these accidents and their severity. In this research, ordinal profit regression modeling is employed for analysis to understand the influence of the variables associated with an accident. This study also uses SPSS software to develop the prediction model.The results indicate that the severity of accidents is related to the driver’s age, meaning that drivers under 35 years old are factors that increase the severity of crashes. Accident severity is also influenced by traffic volume, where a traffic volume less than 4000 VPH has an impact on increasing severity of accidents. Another conclusion is also presented, where it is shown that nonconformity to following distances has a significant impact on the severity of accidents on the freeway.