My top speed of all time was 68.72kph (42.7mph). It was on a about a 2% grade and pedaling like mad in my top gear (52-12 @ 125+RPM). , if i stopped pedalling, i'd loose speed instantly. I have no big clear hills on which to beat that one.
My average average for commuting this yer is 26.23kph (16.3mph) over flat rural terrain on a heavily loaded road bike.