Would you believe consistently under five minutes?
Before you scoff, I live about a mile removed from a State University Extension and the County Sheriff's Department always keeps at least one car in the immediate area. Yes, they have residence dorms.
Regards,
GtG
Actually I would; I used to live about ten to fifteen blocks away from a police station; and a block away from a fire-station. (I'd place the avg response time in the ten to fifteen minute range.)
As with a lot of things, the 'terrain' is an important factor. Even so, many places don't have that sort of relationship. I read somewhere that the national average was above 10min, but I don't remember the number.