TURNOUTS: Description of Important Terms used in Turnouts


It is an arrangement of points and crossings with lead rails by means of which rolling stock may be diverted from one track to another.

Main features of turnout
Main features of turnout

Main features of turnout
Main features of turnout

Description of Important Terms used in Turnouts

1. Lead of turnout : 

It is a distance from the theoretical nose of the crossing to the heel of the switch measured along the straight.

2. Overall length : 

It is the distance from the end of stock rail to the heel of the crossing measured along the straight.

3. Left hand turnout : 

It diverts a train to the left of the straight main line or of the more important line in the case of a turnout from a curve. A right hand turnout does the same in the right direction. In both LH and RH turnouts, the built up crossing used is left handed, i.e. has the splice rail on the left.

Symmetrical split Turnout: 

In this layout the straight track is diverted into two opposite direction using the same radius for both the track of the turnouts. Since the direction is divided equally on both side, the crossing centre line coincides with the centre line of the straight track. 

This is contrary flexure layout in which the degree of the turnout curve will become half and the radius doubled. Lead of the turnout will remain the same. Further details can be worked out applying the principle of ordinary turnout.

This type of layout is used at way side station on end of loop line to provide sand humps also known as snag dead end. Even by using 1 in 8½ layouts, one gets the radius of 1 in 12 turnouts, which is the minimum prescribed for the movement of passenger trains. The sand hump also diverts away the runway vehicles there by improving the safety on the main line.

Symmetrical split Turnout
Symmetrical split Turnout

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