“…Thus many previous studies have focused their emphasis on the likelihood of accidents with those factors, among which human factors from human skills (Sivak, 1981), driving fatigue (Di Milia et al, 2011) and age and gender (Bener et al, 2013) have been given considerable attention. Moreover, some have studied the weights and bumper of vehicles (Gattis et al, 1996;Matsui, 2005) and some have investigated the effects of weather conditions and traffic composition on the occurrence of accidents (Bergel-Hayat et al, 2013;Ramírez et al, 2009), but the important role of roadway geometric design is often neglected.…”