This study is part of an effort by the National Highway Traffic Safety
Administration (NHTSA) to determine the accuracy of the VASCAR-plus speed measurement device. VASCAR-plus is used extensively for speed law enforcement by state and local police. VASCAR-plus calculates average speed using the basic formula: Speed = Distance/Time. The VASCAR-plus manual claims an overall speed measurement accuracy of +_ 1%. This accuracy was recently challenged. This study determined the accuracy of VASCAR-plus time, distance, and speed measurements. Two VASCAR-plus units were electronically tripped (no human operator) to determine the timing accuracy. Six VASCAR certified officers participated in a study to determine VASCAR-plus distance measurement
accuracy. Eight VASCAR certified officers participated in a series of studies to determine VASCAR-plus speed measurement accuracy. The results of these studies show that VASCAR-plus does not have an overall speed measurement accuracy of +_ 1%, but that a + 2 mph upper 90th percentile tolerance limit (95% of the speed errors are
less than + 2 mph) is achievable when the speed measurement is 4 seconds in duration for stationary methods (angular and parking), and is 5 seconds in duration for moving methods (following and approaching from the rear).
In a previous study (Analysis of VASCAR, DOT HS 807-748, May 1993), it was found that the VASCAR-plus timing mechanism was biased against the speed li...
In a previous study (Analysis of VASCAR, DOT HS 807-748, May 1993), it was found that the VASCAR-plus timing mechanism was biased against the speed li...
In 1903, New York City Police Commissioner William McAdoo introduced what was perhaps the first modern speed enforcement technique. As described in "T...
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United States Department of Transportation
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