A racial disparity in vehicle stops is not proof of racial bias, because people of different races sometimes commit a disparate amount of traffic violations. For example, a double-blind camera study of 26,334 drivers in NJ found that police stopped white and black drivers at the same rate that they exceeded the speed limit by 15 mph. However, 2.7% of black drivers exceeded the speed limit by 15 mph, as compared to 1.4% of white drivers. A study conducted in Oakland, California, found similar results.