I've kept track of my average speeds for quite a while now. My truck has a hour trip meter that I use for each tank. It runs whenever the key is on. I've posted my average speeds for quite a while in my fuel log.
My average has been between 25 & 31 mph for most tanks.
Several people have been shocked at those numbers, but I think that sounds lower than it is. I suspect most people's average speed is lower than they think it is because they think of their average
cruising speed, which is much higher than average speed.
So to all my fellow ecomodders out there, post your average speeds if you keep track of them. Not what you think it is, but your actual numbers (over at least a full tank). I suspect most "commuters" are well under 40 mph, but maybe I'm wrong.
FYI, the EPA city cycle has an average speed of 21.2 mph, the highway has an average of 48.3 mph. Even the average of the new "high speed" cycle is 48.4 mph. See details here:
http://www.fueleconomy.gov/feg/fe_test_schedules.shtml