Average speeds only make sense when all the variables, remain constant. Gradient, wind, temperature, equipment and age etc will affect avg speeds.
With my age a constant, my average speed will vary by more then 8mph between a hilly, winter training ride and 10 mile timetrial on a lightweight bike and good weather conditions.
If the age factor becomes a variable, comparing seasons best times fo a 10 mile TT over 50 years, my avg drops by 5 mph from 25mph to 20mph.
So I conclude that comparing avg speeds is meaningless.
However to contradict myself, I use the avg speed metric on every ride, but only to compare rides on the same routes.
With my age a constant, my average speed will vary by more then 8mph between a hilly, winter training ride and 10 mile timetrial on a lightweight bike and good weather conditions.
If the age factor becomes a variable, comparing seasons best times fo a 10 mile TT over 50 years, my avg drops by 5 mph from 25mph to 20mph.
So I conclude that comparing avg speeds is meaningless.
However to contradict myself, I use the avg speed metric on every ride, but only to compare rides on the same routes.