My last solo ride, 40 miles I averaged 18.5 mph with an average HR of 164. Only 720ft of climbing and very little wind. This is a 9.2 mile loop around a lake. Depending on what direction the wind is blowing out of AND if I join a couple of pacelines my averages can vary from 16.3 mph to 19.6 mph. My best speed average in 27 miles was 20.2 mph on the same course but everything was perfect (no wind, 72 degrees, low humidity and I felt really good that day). On my more local rides of 40-54 miles I'm lucky if I break 17 mph averages mainly because of the 2000+ feet of climbing.

With that said, average speed means very little when compared to other data...