Originally posted by Squint
Well, how would you compare a 2 hr ride in the mountains with a half hour ride on flat terrain?
Using HR and time in combination is adequate and better than average speed. Average speed is not going to account for wind, terrain, riding solo vs. in a group, etc. In training logs, HR and time will most definitely be recorded with no one really caring about average speed.
The reason average speed is included is not because it's useful but because it's easily calculated from distance and time and it can be included at no extra cost.
I find it amusing when recreational riders blow through stop lights and otherwise ride recklessly trying to set a new personal best average speed. Just wait for a windless day, geez.