Chris Carmichael has a system calibrated off a pair of all-out 8 minute efforts which are logistically and physiologically easier to accommodate than Friel's 30 minute time trial.

http://trainright.com/wp-content/upl...scriptions.pdf

His book _The Time-Crunched Cyclist: Fit, Fast, Powerful in 6 Hours a Week_

http://www.amazon.com/The-Time-Crunc.../dp/193403083X

includes separate plans preparing for races and long distance rides for both new and experienced riders.

Whatever you do, skip the heart rate formulas (ex maximum is 220 - age) because people vary too much (two standard deviations get you between 196 - age and 244 - age) to be useful

Carbonfiberboy's recomendation of Friel's training bible is great - that's the canonical reference for cycling training.

Regardless, pay attention to the lower intensities too. You need rest days to be fresh enough for your hard efforts, rest weeks to allow for super compensation, and rest months. One workout past zone 4 a week can deliver better results than more.