I averaged 19.62 once, but that is with a computer that stops the clock when you are not moving. You still get slowed down from decelerating/accelerating around lights and stopsigns, but time spend not moving doesn't count against you. Normally, I get 15-16mph averages. Thats with only about 400ft of climbing total over 10mi. If you could average 20mph on total time, I think that would be a pretty impressive feat if you have any stop signs or red lights on your commute.