It's different everyday. Depends on the bike I ride. How hard I want to ride. The wind, the temp, the traffic. Best average speed was 37.5kph for the 10.5km's but that was almost a TT like effort. Helmet camera video of my fastest ever commute is here. http://www.vimeo.com/6217227 On a regular day where I keep my heart rate between 120-140 I usually average 30-33kph. Thats on a cyclocross bike with knobby cross tires or a mountain bike with 1.5" slicks.