My commute is right at 13.10 miles door to door over good roads, with a few longish, but shallow grade hills. I also have a few heavy trafficed intersections I have to turn on to and navigate, and some straight thru traffic lights. I commute on a classic lugged steel Italian bike, carrying a backpack, and eventhough the few hills take some out of me, my time is usually one hour and a minute to an hour and three minutes. The average computer speed is about 12.7 mph on this commute. I just started this commute too, so later on I imagine my average speed would probably increase as I get more use to it.

My previous commute was 8.83 miles round trip, and usually did it in about 40 minutes, with an average speed of 13.7 to 14.5 mph. I can do it faster, even with a 17 mph average speed, but all I want is a good workout and not necessarily kill myself. These 20 mph 10-mile commutes other posters claim are beyond my fitness level at this point, eventhough I commute over 2000 miles a year.

I still love to bike commute though, and have been doing it almost every day for the last five years.