effect of adverse weather conditions on vehicle braking distance of highways

the effect of adverse weather conditions on the safety of vehicles moving on different types of roads and measuring its margin of safety have always been a major research issue of highways. determining the exact value of friction coefficient between the wheels of the vehicle and the surface of the pavement (usually asphalt concrete) in different weather conditions is assumed as a major factor in design process. an appropriate method is analyzing the dynamic motion of the vehicle and its interactions with geometrical elements of road using dynamic simulation of vehicles. in this paper the effect of changes of friction coefficient caused by the weather conditions on the dynamic responses of three types of vehicles: including sedan, bus, and truck based on the results of adams/car simulator are investigated. the studies conducted on this issue for different weather conditions suggest values ranging from 0.04 to 1.25. the results obtained from simulation based on adams/car represent that the friction coefficient in values of 0.9, 0.8, 0.7, 0.6 do not effect on braking distance significantly and it is possible to attribute them all to dry weather condition. however, as it was anticipated the values of 0.5, 0.4, 0.28 and 0.18 have significant differences in braking distance. hence, the values of 0.5, 0.4, 0.28 and 0.18 can be attributed to wet, rainy, snowy and icy conditions respectively.