When I was living in Okinawa I had a short warm up followed by a big downhill at the beginning of my commute going both ways. Of course this also meant a big uphill after a ride around the edge of the bay.

When conditions were right I could hit over 40 on these downhills. The fastest I ever got up to was 42.something mph.

Here I have no hills and am towing the utility trailer much more often. I'm doing good to get much over 20.