Guard rail (rail)

In rail transport, guard rails or check rails are rails used in the construction of the track, placed parallel to regular running rail to keep the wheels of rolling stock in alignment to prevent derailment. They are generally used along areas of restricted clearance, such as a bridge, trestle, tunnel, or level crossing. They also help to minimize damage to the structure and allow easier post-accident cleanup.
History.
Although guard rails in some form have been used as long as there have been trains, the precursor of the guard rails we have today was detailed in , filed in 1893 by Gorham B. Ames, based in Laconia, New Hampshire, USA.
Sharp curves.
On sharp curves, guard rails may be placed inside the inner rail, where they engage the back of the flange of the wheel on that side.