On much of Route 2 in Massachusetts, the posted speed limit is 55 mph, but the median speed of cars is about 70 mph, and I don't see any police. If you are not

On much of Route 2 in Massachusetts, the posted speed limit is 55 mph, but the median speed of cars is about 70 mph, and I don't see any police. If you are not going to ticket people for driving X mph, your speed limit should be at least (X-10) mph (in this case of Route 2, 60 mph). Otherwise posted speed limits have little meaning but do enable police to stop people capriciously.