I use to ride my bike to work, an old steel schwinn, on my way back i'd get on this long flat road that had recently been paved. At night there is no wind...i could hold 33 for the entire length, which if i had to guess was 5-6 blocks. Could never do it in the daytime with any wind though.

That frame was huge though, i think the longer cranks really helped...my new bike is smaller (the proper size) so i'm still getting use to it.