Section II. Guard Rails
When a train is derailed, the danger of more serious consequences, such as the train's falling off a bridge
or crashing into a station platform or building, is ever present. To reduce the chances of such occurrences, guard
rails are used to keep derailed rolling stock from leaving the ties. They are placed between the running rails to
catch derailed wheels and prevent the equipment from overturning or leaving the ties at critical locations. This
section explains the location of guard rails and their sizes and sources.
Although guard rails are useful when properly placed, they should not be installed indiscriminately. The
presence of guard rails complicates maintenance work, making their overuse undesirable. Their most frequent
and important location is on bridges, although they may be placed beside running rail near station platforms
where such tracks are on extremely sharp curves or where train speeds are high. They are often placed at tunnel
entrances, especially if the tracks leading into the tunnels are curved. The guard rails may extend throughout the
length of the tunnel if it is shored with timber or steel. They lessen the chance of derailed equipment damaging
shoring and causing a tunnel to cave in on the engine or cars. In theaters of operations, when rail is in short
supply, guard rails are not to be used on main-line curves unless the curvature is 15 degrees or more.
Guard rails are installed on trestles 40 feet or more in length and on all open-floor deck bridges. On these
bridges, the track structure is fastened directly without ballast, and there is no supporting structure above track
level. For shorter bridges, guard rails are installed only if the track over the span is on a curve greater than 4
degrees. Look ahead to figure 5.2 where these bridges are illustrated.
On a single-track bridge, two guard rails are installed, each 10 inches from the gage side of its adjacent
running rail. Figure 4.2 shows the proper location of guard rails on a single-track bridge. Double-track bridges
require only one guard rail per track, placed adjacent to and 10 inches from the rail most distant from the edge of
the bridge. Only two guard rails are needed on multiple-track bridges, one on each of the outside tracks, because
the running rails of adjacent tracks act as guard rails for the inside track or tracks.