I used to think like this. The last time I thought it was a about two years back. I was driving down our road as a cop rolled on past us so I remark to my wife something along the lines of what makes them think they can drive like that? A minute later we (almost) get home to find that they were responding to a fire at our apartment block. Just because a cop car doesn't have it's lights on doesn't mean it isn't responding to an emergency. These days we live on the other side of town and every day I drive past the county government center. The Sheriff cars are always driving at a reasonable speed around there. I've never once seen them going 10MPH over the speed limit.