In some jurisdictions, VASCAR is the method that the police use to pull people over for speeding. VASCAR speed detection compared to other forms of detection is actually fairly unreliable. There are defenses that can be used against speeding tickets where the speed was measured by this method.
VASCAR stands for Visual Average Speed Computer and Recorder. The concept is that there are two points that your car is measured on. Think of this as a beginning point and ending point. The time it takes you to travel through these two points is calculated giving an average speed.
The reason that it’s fairly inaccurate is that it depends on human interaction. The officer must start the unit when you come to the beginning point and stop the unit at the end point. If started too soon or ending too early, you will be recorded for going much faster than you really were.
There are a couple common defenses. The first involves asking for the distance and time that you were alleged to have traveled. Calculate this distance yourself to see if it’s accurate. There are cases where it has not been accurate.
Another involves a defense against the VASCAR unit itself. These have to be checked and recalibrated from time to time. If this particular unit has not been checked, it’s unreliable in court.
It’s a good idea to find out what model number the unit it. With some research you might find the operational guide or manufacturer’s guide to the unit. This will let you research what specific flaws this unit might have which can be brought up in court.
Like many tickets, conditions such as fog or rainy weather can be brought up. These could impair the officer’s vision which may have made it so that the VASCAR unit wasn’t measuring the accurate distance.