"You mean I cannot exceed the speed limit to pass another vehicle? I thought there was a cushion of a few extra miles per hour to pass a vehicle."
I have heard this question or explanation come from drivers who been pulled over for speeding. For clarification, you can never exceed (or go faster) than the posted speed limit. If the speed limit is 55 mph, meaning when passing another vehicle, you cannot go faster than 55 mph to pass them.