Originally Posted by berner

http://bikecalculator.com/veloUS.html
There are a number of calculators on the web that, given initial parameters of some variables such as weight, slope, aero bars and others, will predict speed or power required, calories burned and other variables. My favorite calculator is out to lunch today but the one linked to above works fine.

If you play around with it you will find that power required for a given speed varies as the square of the speed, I believe. This means that to go twice as fast requires four times the power. This being so, a seemingly small increase in speed,say from 22 MPH to 24 MPH requires a surprisingly large increase in power output. The big lesson here is that as speed increases to near the top of our individual range, we need to be extra stingy about using up our available power and endurance.

This is all very interesting and an exercise in discipline. I find I get sucked into going too fast repeatedly. I hope you are a better learner than I am.