Common place here in Sac as well. Usually black and young. The whites that speed are usually driving something that they feel gives them the right to cut you off. We won't even go into the cell phones.
By reputation, speed limits are enforced more strictly in some stretches of NJ highways than others. Logically, if most motorists speed, it follows that the racial profile of those caught speeding should be nearly identical to that of all the motorists (if the speeding detectors were ideal). Perhaps the statistical results reflect a racial difference in learning where the speed traps are in NJ.