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Five collisions were staged in order to evaluate PC-Crash, a simulation program used for investigating motor vehicle collisions. Both vehicles were moving in all of the staged collisions at 1:1 or 2:1 speed ratios. Pre-impact speeds ranged from 19 to 56 km/h. Two separate methods were used to test the validity of the simulation program. Firstly, collision parameters were calculated from measured data, and used as input to the PC-Crash collision model. Secondly, the post-impact vehicle paths and rest positions were used to determine the pre-impact speeds. There was agreement between measured and simulated collision dynamics. Using the PC-Crash "Optimizer" to reconstruct the five collisions, the error in calculated pre-impact speeds of the ten vehicles ranged from-3.3 to +4.1 km/h. Vehicle speeds were determined based on post-impact rotation and paths, without detailed information on the braking from each wheel or the actual collision coefficient of restitution.

The sun can be a substantial glare source when shining in a driver's eyes when the sun is low on the horizon after sunrise or before sunset, or at virtually any time during daylight hours if the object of concern presents itself at the same altitude and azimuth as the sun. Second, the ambient light levels during the civil twilight period, either before sunrise (dawn) or after sunset (dusk), are brighter than complete darkness, yet are less than normal daylight driving conditions. Methods are presented for calculating the times of sunrise and sunset, the times of civil twilight darker limit, the angular position of the sun, for any time, and date, and for estimating the natural light levels at the time of the incident, to enable an assessment of driver visibility.