Straight Track.

The tendency of a body in motion is to follow a straight line. Hence, on a straight track the tendency of a travelling vehicle is to remain in a position central with the track. Under ideal conditions, therefore, there are no reasons why an unlimited speed should not be permitted, on any gauge, on a perfectly maintained straight track with well-balanced stock (See Beaton, on “Speed of Trains”). “On a straight track with easy curvature no speed restriction would seem to be necessary,” says Shannon in “Derailments and their Causes.”

Under normal conditions there will be no pressure between the wheel flanges and the rail.

The centre of gravity of the train, and of each truck of the train, must move in a straight line on a straight track of uniform grade. In other words, the train must move in a straight line parallel with the track.

The irregularities in supposedly straight track cause trucks to oscillate, pitch and twist.