Okay... when Doc is outlining his plan to Marty,

he shows him on the map the stretch of track he plans

to use, and says "This stretch of track runs three miles out

to Clayton... Shonash Ravine" Did you catch that??

THREE miles. Now.. feel free to flame me if I'm wrong,

but an object moving at 60 miles per hour, will

travel 3 miles in 3 minutes. A train under constant

acceleration up to and indeed *past* 60 miles per

hour will need a hell of a lot more than three miles

of track to reach 88 mph. I'm sure if you time

the whole sequence and work it out mathematically,

you'll find the train should have plunged into the

ravine after about 5-6 minutes, without ever

reaching 88mph!