I think I remember seeing here some formula to calculate how much of your driving was "city" as defined by the EPA, but I can't find it with a search. If anyone knows what I'm talking about, I'd appreciate a link to the post. Thanks.
I just ballpark my estimates at 50/50 city and highway. My 23 mile commute has 19 stop signs/stop lights each way, and all but 4.5 miles are 55 mph speed limit.