Reactions to Brad Keselowski's final pit stop in this year's Bristol night race have given me the impression that most NASCAR fans are totally unaware of how pit road speed is measured. I would love to clear up these misconceptions.
Visual Average Speed Computer and Recorder (VASCAR) is a system used by police departments and NASCAR as a means of measuring speed. Instead of determining speed instantaneously like radar and LIDAR, VASCAR measures a vehicles elapsed time traveling between two waypoints with a known distance between them. A computer divides the distance traveled by the elapsed time to determine average speed. NASCAR indicates these waypoints by painting clear white lines across pit road and/or a red line on the straightaway-side pit wall at intervals of 150 feet (45.72 meters) with few exceptions for pit roads that have been extended in the last decade. There is no need to trust me on this; the lines are visible on Google Maps.
The controversial pit stop is an example of all that is wrong with the system. Since it measures average speed instead of instantaneous speed, it is very easy to select a pit stall that allows you to break the pit speed limit in actual speed as long as your average speed is copasetic. In the Keselowski affair, the #2 car's stall was near the penultimate waypoint before the pit exit line. Brad was able to drive as fast as possible at the pit exit line because he was slow enough at the penultimate line that it lowered his average speed to less than the cars he was passing.
The controversial pit stop is also an example of all that is right with the system. Paul Wolf probably spent hours comparing the acceleration rate of his car to the pit stall locations at Bristol so he could exit the pits as fast as possible. It certainly violates the spirit of the rule book, but as the letter of the rulebook limits NASCAR to measuring average speed it is entirely fair to make an argument such as, "That's not cheating, tha's innovating." It's so awful, that I kind of like it!
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