Originally Posted by DrIsotope

I too have the dissonant relationship with my average speed-- I know that a big part of it is outside my control, but I still kill myself on some rides trying to keep that number up. If there are a lot of intersections you have to cross, your average speed is going to suffer. It doesn't take more than a couple of stops to really bring the average down. I have numerous lap-routes I do around town that never turn left. I play a game with myself (thanks to a head unit with an excellent map) called "red light, turn right," where I go as long as possible without stopping/unclipping. Even with the slowing for intersections and going into unknown territory, average speed will usually increase ~1.5mph.

Also, speed up hills is far more important than the speed going down them. Say you're climbing a 1 mile long hill (say a 5-6% grade,) and it takes 10 minutes (6mph.) But when you turn around and come back down, it takes 2 minutes (30mph.) That 30mph descent can't make enough of a difference-- it still took 12 minutes to go 2 miles, for an average speed of 10mph. If you held onto a car and did the descent at 60mph, that wouldn't even get you to an 11mph average. Now say you hammered your guts out and got to the top of the hill in 6 minutes (10mph) and coasted down at 25mph. That's 8m24s to go 2 miles, an average speed of 14.3mph. Coasting down the hills takes no energy, and is really only "losing" a few seconds.