RUNNING RAIL. The rail or surface on which the tread of the wheel bears.
RUNNING TRACK. A track reserved for movement through a yard.
SAFETY APPLLIANCE. Any one of several specific components which should be on railcars.
Safety appliances are for train crewmembers and other persons whose duties require them to be
on or around the equipment. Safety appliances on cars include hand brakes, handholds, ladders,
uncoupling levers, sill steps, and safety railings.
SHOULDER (TRACK). The portion of the ballast between the end of the tie and the toe of the
SIDE BEARING. A load-bearing component, located either on the truck or bolster, and
arranged to absorb vertical loads arising from the rocking motion of the railcar. There are various
types of side bearings ranging from simple flat pads to complex devices which maintain constant
contact between the truck bolster and car body.
SIDE SILL. The outside longitudinal members of the underframe which form the outer edges of
the railcar body.
SIDING. A track auxiliary to the main track.
SINGLE TRACK. One main track on which trains operate in either direction, distinguished
from double or multiple track.
SOUPING. A condition in which the engine blows oil out the exhaust. This condition is
generally caused by glazed cylinder walls which prevent the piston rings from properly seating.
SPARK SHIELD. A plate located on the bottom of a railcar over the wheels designed to deflect
sparks away from combustible car components.
SPEED, NORMAL. The maximum speed authorized.
SPEED, RESTRICTED. A speed reduction defined by directive.
SPRING SWITCH. A track switch with a spring mechanism that automatically returns the
switch points to a normal position after they have been displaced by passage of railcars in a
trailing point movement.
STUB TRACK. A form of side track connected to a running track at one end only and usually
protected at the end by some form of bumping post or other solid obstruction.
SURFACE (TRACK). The condition of the track as to vertical events or smoothness.
SUSPECT CAR. A railcar of unknown contents.
TANGENT (TRACK). Any straight portion of a railway alignment. Tangent track means
straight track with no curves.
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