One day last week I averaged (Moving Speed, Garmin Computer) 20.2 on the way in to work, and 20.3 on the way home. It's a 5.3 mile commute each way. On the way in it's free sailing for 4 miles at which point I get into downtown and the traffic lights and stop signs start appearing.

On this day I had the good fortune of catching every green. I slowed to less than 5 mph for the stop sign (3 way stop), but there were no cars so I continued to roll and didn't unclick. The ride home is a bit more complex this time of year (tourist season), downtown is mayhem. That said, once I got out of downtown it was free sailing, and the prevailing wind was my friend not my enemy. I was busting my butt to do this to see if it could be done, and normally I don't like to push that hard coming into work.

As a side note, my average overall speed was 20.2 mph both directions.