Point and Crossings are peculiar arrangement used in permanent way (railway track) to guide the vehicle for directional change. Broadly point and crossing assembly consists of three main components namely Point
and Crossing element
. A point consists of one pair of tongue rails and Stock Rails with necessary fittings.Crossing is a device in the form of V-piece introduced in the track to permit movement of wheel flange at the inter section of two running lines.It has gap over which the wheel tread jumps.The track portion between point and crossing is is called lead.
The points and crossing are the vital components of track asset; necessary for diversion of traffic from one track to another track, such diversion may be necessitated for giving precedence to faster trains in the same direction, giving passage to a train moving in the opposite direction or for connecting places not on the direct line of track. Hence the design, laying and maintenance of the points and crossing have a significant influence throughout the section.
Constituents of the points and crossing
The switch assembly, the crossing assembly and the lead portion beyond the turnout, turn-in- curve is also important assembly.
- Turnout- The term denotes points and crossing with the lead rails.
- Tongue rail - It is tapered moveable rail, connected at its thickest end to running rail.
- Stock rail – It is the running rail, against which a tongue rail functions.
- Switch – A pair of tongue with stock rail with necessary connections and fittings.
- Points – A pair of tongue rail with their stock rails are termed as points.
- Crossing – A crossing is a device introduced at the junction where two rails cross to permit the wheel flange of railway vehicle to pass from one track to another track.
- Heel of switch – It is an imaginary point on the gauge line midway between the end of lead rail and the tongue rail in case of loose heel switches In case of fixed heel switches, it is a point on the gauge line of tongue rail opposite the centre of heel block.
- Lead – The track portion between heels of switch to the beginning of crossing assembly is called lead. ix) Turn – in – curve: The track portion between the heel of crossing to the fouling marks is called turn – in – curve.