Over my 8.5mi totally flat commute between 20-21mph average moving time. 19-20mph elapsed time (i.e including stop time at lights)
When I was riding faster in April-05 I hit 23mph auto average, 22mph elapsed a few times.

Just as an aside over the past 22 months of commuting I just calculated I've spent a total of 27 hours and 24 minutes stopped at red lights.

Al