Its not very accurate, they have to clock you between the intervals. Vascar is usually very easy to fight since its considered highly inaccurate due to discrepancies in the ability of the officer to hit the stopwatch correctly.
IMO, if you pay attention to the markings on the road, VASCAR is easier to deal with since it is VERY predictable (They use the same spots all the time) and also, if you notice that you're going into a trap too fast, you just need to slam the brakes to slow down enough to make your speed average out as legal.
In PA, Locals have to permit you at least 10MPH over the limit on their Vascar readings to take into account the error. Usually if a VASCAR ticket is written for under 10mph, alot of times the department won't even bother to send an officer in court since its too easy to fight it.
Vascar can be a tad bit fun at times. In PA, there's a little game some like to play where you purposely come into a VASCAR trap hot, then SLAM the brakes and crawl at walking pace over the second line. Cop's reading comes out as legal. They know you were speeding, but cannot do anything since your speed averaged out as being within the legal limits.
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