When I was commuting a lot more often, I am not a fast rider, but I didn't get passed that often either. Granted, I was on a fixed gear cyclocross frame but I made sure I had slick 28mm tires. I would average maybe 15 mph? on a good day. Into Boston, over 7-10 miles.

Then I see numbers like 20+ mph in commuting forum?? I am thinking these guys are fast riders to begin with but their commutes have to be in rural/suburban flat terrain, no?

Can some of you share your routes, please? For inspiration... Would anyone average 20+mph commuting into a decent-sized city?