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Relative velocity detection thresholds of drivers are one factor that determines their ability to avoid rear-end crashes. Laboratory, simulator and driving studies show that drivers could scale relative velocity when it exceeded the threshold of about 0.003 rad/sec. Studies using accident reconstruction have suggested that the threshold may be about ten times larger. This paper discusses this divergence and suggests reasons for it and concludes that the lower value should be used as a true measure of the psychological threshold for detection of relative velocity.

This research compares vehicle dynamic simulations in PC-Crash 8.2 to data recorded during instrumented handling tests conducted by Mechanical Systems Analysis Incorporated (MSAI). The handling tests, which were used to examine rollover stability in a 1998 and a 1999 Ford Explorer, involve rapid steering inputs at speeds between 30 mph [48.3 kph] and 60 mph 96.6 [kph]. Vehicle weight, center of gravity (c.g) position, suspension stiffness parameters, tire parameters, steering angle, and vehicle speed data provided by MSAI were used as input for the PC-Crash model. Lateral acceleration, roll angle, roll rate, and yaw rate vehicle response from PC-Crash were compared to the MSAI sensor data. The authors modeled 26 handling tests. PC-Crash appeared to be a reasonable tool for modeling gross vehicle response. In addition, PC-Crash correctly predicted whether or not the test vehicle would experience rollover instability in a majority of the cases.