I know I'm not the fastest guy out there, but I ain't the slowest either.
Today (Saturday), I had to run an errand downtown, not far from where I work. I told my wife, "I'm going to take my bike - it'll be almost as fast as driving." "Really?" she asked, skeptically.
It was a beautiful morning, with just a breeze from the south-west. For this trip, that meant a bit of assistance going downtown, and a bit of hinderance coming home. I would take a minimal amount of gear, and ride my lightest, stiffest, fastest bike. I would also take a mostly urban route, sticking to the roads for the most part, taking trails only where they afforded a shortcut. This also meant avoiding any climbing since I wouldn't be going through the river valley. In short, conditions were pretty ideal for a fast trip, save that I would encounter some stop signs and traffic lights along the way.
My commuter bikes don't have cycle computers, so I don't have a good sense of how fast I normally commute at. My weekender bike does have a computer, so I would be able to keep track of my speed. I kept an occasional eye on the speedometer, and on the way downtown, I was able to consisitently keep up a speed of 35-37 km/h (21.75-23.6 mph), hitting a top speed of 49.4 km/h (30.7 mph)! (That didn't last long.) The way back home was, as expected, slower, and I felt like I was expending more effort to keep my speed above 33 km/h (20.5 mph). Overall, I know I worked significantly harder than I do on most commutes.
When I got home, I checked my average speed according to the computer: 30.7 km/h (19.1 mph). And that's my
moving average. My overall average would be less of course, though I didn't keep track of my overall time. But the conclusion as we all know is: It's the stops and starts that'll kill yer average speed.
I know this isn't a revelation to most of you; it isn't to me either. But it's a question that comes up periodically on this forum, and I thought I would put some real numbers to the topic.
Post script: When I got home, my wife commented, "Huh! that really
didn't take very long." Told ya!
Post-post script: I know I haven't asked a question, so before someone points that out: Would anyone else like to share their similar experience?