I cycle as my primary means of transportation, on a flat-bar touring bike in normal clothes. I average about 12mph. I'm faster than most other cyclists I meet on the road. The only cyclists faster than me are on road bikes and wearing specialist cycling clothing (I estimate about 20% of cyclists where I live).

I could go faster, but then I'd have to change clothes and shower, which would make me slower overall.

GP is responding to the ridiculous assertion that the average RUNNING speed for humans is 11-15 mph.

Even taking into account only young adults, I'm sure most of them can't sprint 11 mph

Counterpoint is if you do 40 mile rides you are most likely already an above average cyclist.