This article is from the Running FAQ, by Ozzie Gontang with numerous contributions by others.
(contributed by Steve Pachuta, firstname.lastname@example.org)
The January, 1996 _Consumer Reports_ has a treadmill review which
features both motorized and nonmotorized models, together with some
useful criteria for evaluation.
Why use a treadmill?
There are many advantages to treadmills, including (1) The most
obvious--weather is not a factor in your training schedule. (2) Training
is possible any time of day--darkness is not a factor. (3) No danger of
getting hit by a car or tripping on a curb. (4) No stoplights, no rabid
dogs (presumably), no hecklers (presumably)! (5) Controlled hill workouts
are possible with adjustable incline. (6) Precise interval training is
possible. This is a big advantage; you just need to set your speed and
stay on the treadmill to run your goal pace exactly.