VASCAR

An operator records the moments that a vehicle passes two fixed objects (such as a white circle or square painted on the road) that are a known distance apart.

A 1991 study by the National Highway Traffic Safety Administration found that VASCAR-plus units produced errors of less than 2 mph if used correctly.

[1] He was inspired to create the device after watching a police car driving dangerously trying to pace a speeder.

[5]: 181  The original version of the device was entirely mechanical, using a governed motor and a gear system to move a pointer to the correct speed value.

Older vehicles, with cable-driven speedometers, are connected to the VASCAR unit with a mechanical-optical adapter which attaches to the cable.

The time and distance registers are completely separate from each other, and each is controlled by a toggle switch, which is operated by the traffic officer.

Later systems combined the control and computer sections into a single unit, and replaced the earlier Nixie tube displays with LEDs.

Some VASCAR systems have included the ability to set a specific distance, allowing a traffic officer to avoid having to measure each time that stretch of road was checked.

It is also possible to retain an earlier measurement, to be used with multiple vehicles (for instance, when spending a morning enforcing speed in a school zone).

VASCAR, however, can provide an accurate speed clock under any conditions in which both a start and a stop point can be identified.