Investigating the Effect of Road Characteristics on Fatal Crash Count and Crash Severity; Case Study: Birjand-Qayen Route

Motor vehicle crashes are currently among the ten major mortality factors all around the world. iran follows a similar pattern and has a high annual rate of fatal crashes. the majority of these fatal crashes occur on rural routes, particularly on twolane roads. in this study, the effective factors on the occurrence of accidents on birjandqayen route (south khorasan province, iran) is studied. in order to investigate the effects of being in twolane segments, horizontal curves with more than 2% slope, and segments with insufficient lighting, on the fatal crash count and crash severity, standard poisson regression model (fatal crash count per km as the dependent variable) and standard ordered logit model (severity of crashes as the dependent variable) were calibrated using the 20132016 data. zeroinflated negative binomial and zeroinflated poisson models were also applied to investigate the effect of true zero in fatal crash count modeling. furthermore, a panel analysis of crash severity ordered logit model was carried out to consider the spatiotemporal effects. the results of the fatal crash count modeling showed that three or fourlane segments (compared to twolane segments) reduce the number of fatal crashes, whereas curved segments with more than 2% slope (compared to straight segments) increase this number. moreover, according to the crash severity model results, segments with sufficient lighting as well as threelane or fourlane segments (compared to twolane segments) reduce the severity of crashes; whereas crash severity in curved segments with more than 2% slope (compared to straight segments) is increased.