A person on railroad tracks hear a train approaching, looks behind him, sees the train
and then freezes on the tracks in fear. The train "outruns" its sound--which
means that by the time you hear it, it is virtually on top on you. If a train engineer
sees you on a track, he or she will blow the whistle. Often it takes more than one blast
to get the average person's attention, say train engineers. But trains can't stop the way
motor vehicles can. A freight train has about 100 cars, weights 12 million pounds, and
takes a full mile to stop. An optical illusion happens with tracks. When you see a train
coming, it looks as if it is traveling half as fast, and is two times farther away from
you than it really is. For example, if it is going 60 miles per hour and is half a mile
away, it looks as if it is traveling 30 mph and is one mile away.
Operation Lifesaver, in MSC Health Action News, Vol XIV, No. 3, March 1994, p. 4.