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 limit violator. The VASCAR speed reading was higher than the actual speed. At that time, it was suggested by the Law Enforcement
Community that the timing mechanism be modified so that it would be in favor of the violator (VASCAR speed less than actual speed). Since that time, the manufacturer of VASCAR-plus has changed the timing device. The study described in this report was conducted to determine the accuracy of the new timing mechanism. To determine actual timing errors for the VASCAR-plus with the new timing method, a series of
bench tests were performed similar to those described above. Both a Nicolet oscilloscope and a VASCAR-plus unit were simultaneously triggered using two trip switches. The oscilloscope sample rate was set to 1 msec. Two VASCAR-plus units were tested. A total of 50 tests was performed on each unit. With the new timing data collection method, when the time switch is turned off the VASCAR computer collects data for 2 more 36 msec time steps. The timing errors for this method should range from 36 to 72 msec. Since these timing errors are positive, they would be biased in favor of the violator.
This study is part of an effort by the National Highway Traffic SafetyAdministration (NHTSA) to determine the accuracy of the VASCAR-plus speed measur...
This study is part of an effort by the National Highway Traffic SafetyAdministration (NHTSA) to determine the accuracy of the VASCAR-plus speed measur...
This report presents a synthesis of research findings on the safety effects of speed, speed limits, enforcement, and engineering measures to manage sp...
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