چكيده به لاتين
According to official statistics in Iran in 2018, it is claimed that there were approximately a total of 17000 fatalities in traffic crashes. Among these statistics, the motorcycle users and pedestrians show noticeable susceptibility in severe crashes that about 50% of all crash fatalities belong to them. The highest injury severity of occupants in an accident is frequently taken into account by the researchers for identifying the influential factors on the accident severity and just one aspect of the accident is considered at a time. For performing a comprehensive study of the accident severity, accident size can be utilized. So, the objective of this study is to identify the influential factors on the accident severity and accident size of susceptible road users using structural equation modeling. In this regard, 11387 accident data for the motorcycle involved accidents and 3718 accident data for the pedestrian accidents was used. The considered accidents occurred in urban roads of Isfahan province between 2011-2018. The results show that the factors of road (estimate=-0.162, t-value=-2.5), environment (estimate=0.59, t-value=8.68) and vehicle (estimate= -0.144, t-value=-7.79) have significant effects on accident severity which means that two-way undivided roads, highways, day time, head-on collisions, heavy vehicles, old-aged drivers and female drivers influence the accident severity positively in motorcycle-involved crashes. In addition, the factor of vehicle (estimate=-0.418, t-value=-15.79) affects the accident size negatively that the most indicative variable was vehicle type. On the other hand, the model indicated that the factors of road (estimate=0.076, t-value= -1.707), age (estimate=0.517, t-value=8.76) and vehicle (estimate=0.059, t-value=1.826) have positive and significant influence on the severity of pedestrian crashes. The variables of road type, pedestrian’s age and vehicle type influence the pedestrian accident severity significantly. Finally, the results represented that the factors of road (estimate=0.211, t-value=11.8), pedestrian (estimate=0.162, t-value=5.41) and vehicle (estimate=0.872, t-value=8.383) influence the accident size of pedestrian crashes significantly. The two-way divided roads, highways, the contrasting clothing color of pedestrian, female and old-aged pedestrians, heavy vehicles, old-aged drivers and female drivers increase the accident size of pedestrian traffic crashes. This study shows the importance of considering safety improvement measures in two-way roads, traffic control measures in highways, educating the people in the society about the accident safety, the separation of pedestrian and motor vehicle traffic flow and considering the old drivers in policies and programs for mitigating the accident severity.
