UNIT - 4

POINTS AND CROSSING: Components of a turnout, Details of Points and Crossing,

Design of turnouts with examples (No derivations) types of switches, crossings, track
junctions Stations and Types, Types of yards, Signalling - Objects and types of signals,
station and yard Equipment-Turn table, Fouling mark, buffer stop, level crossing, track
defects, and maintenance. 08 Hrs
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Points and Crossings
The points, crossings, turnouts, cross overs etc are all related terms and arrangements that are
used to enable the trains to move from one route to another. They also help in the shunting operations.

Necessity of points and crossings

The points and crossings are necessary to change the direction of trains since the wheels have flanges.
Other factors are:

1. They provide flexibility of movement by connecting one line to another.

2. They help for imposing restrictions over turnouts which necessarily retard the movement
3. From safety point of view also it is important as points and crossings are weak lines in the
track.

Switch

A switch consists of a stock rail and a tongue rail. Switches are tapered rails with the thicker
end known as the heels, fixed to the main track while thinner end known as the toe is kept movable.

Type of switches

There are two types of switches:

1) Stub switch
2) Split switch

Stub switch

In this type of switch, no separate tongue rail is provided and some portion of the track is
moved from side to side. It is an old form of switch and has got many objectionable features in its
performance. It is no more in use and has been replaced by the split switch which is universally
adopted.

Split switch

In this type of switch, a tongue rail is combined with the stock rail. Spilt switches are
classified as below.

a) On the basis of fixation at heel.

i. Loose heel type or articulated type

ii. Fixed heel type or spring type or flexible type

b) Under cut switches

i. Over riding switches

ii. Straight cut switches
Loose heel type/articulated type switch

1) In this type, tongue rails are joined to lead rails by means of fish plates.
2) The two front bolts are kept loose to allow the throw of switch and these bolts are kept tight
when the tongue is open.
3) In this type, heel block, anticreep decives and point lever box are used as shown in figure.
4) It is suitable for short length switches.
-------------------------fig--------------------------------------------

Fixed heel type

1) This switch is an improvement over loose heel type switch.

2) In this, all the four bolts are tight when the tongue is closed.
3) It has quite satisfactory result when long tongue rails are used. Hence it is suitable for long
tongue rails.
-----------------------------fig--------------------------------

Under cut switches

1) In this, the height of the stock and tongue rails is same.

2) It is desirable to cut out a portion of flange at the foot of the stock rail so that the toe of the
tongue rail is accommodated under the head of the stock rail. Such switches are termed as
under cut switches.
3) The above figure shows the old design and modified form of switches.
4) Disadvantage: it becomes weak when flange portion is cut out.
5) It is generally used on narrow gauge lines.

Over riding switches

1) In this type, separate rail sections of stock rails and tongue rails are adopted.
2) The stock rail of heavy section and tongue rail of light section are used instead of cutting the
flange as in case of under cut switches which results in weakening the stock rail.
3) In this, tongue rail rides over the flange of the stock rail at a difference of 6mm. such switches
are termed as over-riding switches.
4) It is generally used for B.G and M.G. tracks.
5) A compound fish plate at the heel is necessary to connect it to the lead rail.
Straight cut switches

1) In this type, the tongue rail is cut straight in the line with the stock rail and hence termed as
straight cut switches.
2) This is done to increase the thickness of toe of tongue rail which increases the strength.
3) This type of switch is suitable for B.H. rails.

Crossing/Frog

It is a device which provides two flange ways through which the wheels of the flanges may move,
when two rails intersect each other at an angle.

Components of crossing

Following are the components of crossing:

a) Crossing/vee piece
b) Point and splice rails
c) Wing rails
d) Check rails
e) Chairs at crossing, at toe and at heel
f) Blocks at throat, at nose, at heel and distance block
g) In some cases, packing below the wing rails at toe and throat.

Types of crossings

It is classified on the following basis:

1. On the basis of shape of crossing

a) Acute angle crossing/ “V” crossing / Frog
b) Obtuse angle crossing / Diamond crossing
c) Square crossing
 2. On the basis of assembly of crossing
a) Spring or movable wing crossing
b) Ramped crossing

Acute angle crossing

1) This type of crossing is widely used and is obtained when a left-hand rail of one track crosses
a right-hand rail of another track or vice versa.
2) If the angle of intersection of the approaching rails is acute angle, it is known as acute angle
crossing.
3) It consists of point and splice rails, wing rails and check rails.

Obtuse angle crossing

1) It is obtained when left-hand rail of one track crosses right-hand rail of another track or vice
versa at an obtuse angle.
2) In this long wing rails do not carry the wheels as in acute angle crossing, but acts as check
rails.

Square crossing

1) When two straight tracks cross each other at right angles, gives rise to square crossing.
2) This type of crossing should be avoided on main lines because of heavy wear due to dynamic
loads.
Spring / movable crossing

1) In these crossing, one wing rail is movable and is held against the vee of the crossing with a
strong helical spring. By doing so, it makes the main track continuous.
2) This crossing is useful when there is high speed traffic on main track and light speed traffic
on the branch line.
3) Spring crossing is not favoured in India because there is a danger of accident in case of spring
failure.

Ramped crossing

1) It is suitable for complicated yard layout which has heavy traffic with slow speed.
2) Clearance between throat to nose is negotiated by use of special manganese steel blocks over
long distance.

Types of track junctions

The important types of track junctions are:

1) Turnouts
2) Symmetrical split/ Equilvalent turnout
3) Three throw switch
4) Double turnout or tandem
5) Diamond crossing
6) Cross overs
7) Single slip and double slip
8) Gauntlet track and fixed point system
9) Scissor cross-over
10) Gathering lines or ladder tracks
11) Temporary diversion
12) Triangle
13) Double junctions
Turnouts

It is the simplest combination of points and crossings which enables one track to take off from another
track. Therefore, the object of turnout is to provide facilities for safe movement of trains in their
direction on both the tracks.

The salient features are:

a) To provide facilities for turning of trains from one track to another.

b) Turnout consists of a pair of points, 2 straight lead rails, 2 curved lead rails, 2 check rails and
a crossing.
c) Depending upon the facilities provided for turning on right or left of main track, the turnouts
are called right-hand or left-hand turnouts respectively.
d) One turnout provide facilities for turning of vehicles/trains in one direction of the main track
only.

Symmetrical split

When a turnout is taken off from a curved track, it is known as a split.

When a straight track is spilt up in two different directions with equal radii, it is known as a
symmetrical split.

Following are the salient features of this track junction are:

a) Radii of the main track curve and the lead curve are equal.
b) The turnout is symmetrical about the centre line.
c) Number of crossings 1 in 6 is generally used.
d) This provides the facilities for turning of trains in both left and right directions of the main
track.
e) It is suitable for locations where turnout from a straight track would take too much of space.

Three throw switches

If the turnout and the main track, turn in the same direction, the curves are said to be in similar
flexture.

When two turnouts take off from the same point of a main straight track, it is known as “Three-throw”
arrangement.

If the turnouts are on either side of the main track. This arrangement is known as three throw switch
with contrary flexture.

If these turnouts are on one side of the main track the arrangement is termed as three throw switch
with similar flexture.
Salient features are:

a) It is unsuitable for main lines with heavy traffic, because use of switches may lead to
derailments.
b) It may be used in congested area where space is not enough.
c) It consists of 2 switches, 2 stock rails, 3 crossings, check rails and combined heel blocks for
both the tongue rails of the switch.
d) This track junction is obsolete these days.

Diamond crossing

When straight tracks or curved tracks of the same or different gauges cross each other at an angle less
than 90º, a diamond shape is formed. So this crossing is called as diamond crossing.

Its salient features are:

a) It consists of two acute angle crossings (α and α1 ), 2 obtuse angle crossings (β and β) and
four check rails.
b) The length of the gap between two noses of an obtuse crossing increases as the acute angle of
crossing decreases.
c) Diamond crossings should be avoided as far as possible on curves as they necessitate
restriction on speed.

Cross overs
When two adjacent parallel or diverging tracks, which may be straight or curved, are connected by
two sets of turnouts, with or without a straight length between them, the connecting line is known as
below.

Salient features are:

a) It consists of two pairs of switches, 2 acute angle crossings with reverse curves, with or
without straight length in between and 4 check rails.
b) Use of reverse curves between two crossings shortens the length of cross-over but its use
becomes limited for low speed sidings.
c) The length of straight portion depends upon the spacing(D) between the two adjacent tracks
to be joined.
d) Cross-overs are useful to change the track; when trains are approaching from one direction
only.

Single slip and Double slip

A single slip is one in which the tracks can be changed from one direction only.

In slip arrangement the trains can move from one track to another.

A double slip is one in which the tracks can be changed from both directions.
Important features of single and double slip arrangement are:

a) It consists of 2 acute angle crossings, 2 obtuse angle crossings, special curved-lead rails and 4
check rails
b) Single slip arrangement consists of 2 pairs of switches.
c) Double slip arrangement consists of 4 pairs of switches.
d) This arrangement enables the trains to travel from one track to another.

Gauntlet track and Fixed point system

Gauntlet track is that arrangement of the track which is adopted when a double track is to be narrowed
over a short distance of the track. This arrangement becomes necessary when one of the double tracks
is under repair or on bridges for economic considerations.

When two lines of different gauges have to cross a river, they are carried on the same bridge by using
3 rails out of which one rail will be common for both the tracks. This save the cost of one extra bridge
or cost of widening the bridge for accommodating two tracks. This arrangement is made by fixed
point system.

Important features of the gauntlet track are:

a) The two tracks are simply laid side by side and have two sets of crossings without any
switches.
b) It is used to economize the cost of a double line bridge.
c) It is also used when part of a double line bridge is under repair.
Scissor cross-over

It is a combination of one cross-over over the other cross-over in the opposite direction. It is done to
enable the trains to change the track from either direction along the main track.

Important features of scissor cross-over are:

a) It consists of 4 pairs of points, 6 acute-angle crossings (α and α 1), two obtuse angle crossings
(β and β1), check rails and straight lengths.
b) This arrangement is useful where enough space for two separate cross-overs is not available
and shunting operations are frequent.
c) This arrangement is very much expensive in initial cost and moreover requires careful
maintenance.

Gathering track or Ladder tracks

When a number of parallel tracks are branched off from the straight track in continuation of a turnout,
it is called a gathering line or ladder track.
 Fig (a): Gathering lines or ladder tracks

Fig (b): Another patter of gathering lines

Fig (c): Herring bone grid pattern of gathering lines

In fig(a), AB sloping line is the gathering line.

In fig (b) and (c) are alternate patterns of gathering lines.
In fig (b), AB and DC are separate gatherers
In fig (c), DC is separate gatherer and AB integral gatherer. This is given the special name as “Herring
bone grid” pattern.

Important features of gathering lines are:

a) The angle of gathering line (θg) in fig (a) is equal to the angle of crossing adopted in station
yards (α1 and α2)
i.e., θg= α1= α2
 b) The arrangement known as “Herring bone grid” is used in marshalling yards and goods yard
where sidings are almost of equal length.
c) The limiting angle of gathering line is given by the relation:

Sin θg(limiting) = S
C

Where,
S=Spacing between two adjacent tracks
C= overall length between the points and crossing

d) Gathering line can be laid if the angle is greater than the crossing angle (α 1 and α2) but less
than the limiting angle (θg )

Temporary Diversion

A temporary diversion is required when the track has to be directed from its original position if some
heavy or time-consuming work required is to be done on original track or track has failed under
floods, etc.

The important features of diversion are:

1) It consists of two pairs of points, 2 acute angle crossings and 4 check rails.
2) Important elements of design of a diversion are:
a) Distance of diversion from existing track i.e, d
b) Radii of the reverse curves on both the ends
c) Gradients (g1 and g2) of the diversion.
3) These diversions are necessary in connection with breaches of track due to floods or for heavy
repairs or rebuilding of a bridge.

Triangle

Triangles are required for changing (or reversing) the direction of engines.

Working:

If an engine is standing at A facing towards B and the engine moves in the direction of arrow [i.e,
from A to C, C to D, then back D to C, C to B], B engine will be facing towards A.

Important features of triangle are:

1) It consists of two simple turnouts (i.e, at A and B) and one symmetrical split at C.
2) This is mainly used for turning the faces of engines where provision of turn-table is costly.
Double junctions

These junctions become essential where two or more main tracks are running and where
branches are taking off from main track.

Important features are:

1) It consists of number of turnouts depending upon the main tracks (2 turnouts) and one or
more diamond crossings again depending upon the main tracks (one diamond crossing)
2) Depending upon number of main tracks and branches taking off from main tracks , many
other junctions of complicated nature can be obtained.

Track Maintenance

Defects in railway track/ Necessity of Maintenance

1. Due to high speeds and loads, the strength of track structure goes down resulting in reduction
of track elasticity, disturbance in guage and alignment and surface level of rails.
2. The track is subjected to affects due to sun, wind and rain.
3. Wear and tear due to moving trains and climatic factors.
4. Due to effects of load and speed on points and crossings, bridge approaches and level
crossings particularly on curves.

Maintenance of track

Maintenance of track can be divided into

1. Daily maintenance
2. Periodic maintenance

In case of Daily maintenance, gauges are appointed. The track is divided into a number of sections of
about 5-6 km length. The gauge maintains the track throughout the year. While in Periodic
maintenance it is carried out once in two to three years. During this the gauge, levels, alignment,
points and crossings, etc. are thoroughly checked and remedial measures are taken.

During maintenance, the following aspects are taken care of

1. Packing- of stone ballast

2. High joints- they are caused such that the level of joint is higher than track
 3. Blowing joints- it is caused when a joint is situated over loose and dusty ballasts.
4. Buckling of track- caused due to insufficient gaps widths, temperature variations and over
tightening of fish plates
5. Corrugation of rails- formation of openings on rails
6. Drainage
7. Cleaning of ballast
8. Renewal of rails
9. Renewal of sleepers
10. Maintenance of fittings
11. Maintenance of rolling stock- like locomotives, coaches, etc.
12. Maintenance of points and crossings
13. Maintenance of level crossings and tunnels, etc.

Level crossing

When a railway line and a road cross each other at the same level, it is called a level crossing. The
surface of the road is kept at rail level and grooves are left in the road surface along the inner edges of
the rails for the movement of wheel flanges. These grooves are provided with guard rails which are
spiked to wooden sleepers. The type of facilities provided at level crossing depends upon its
classification which in turn depend upon the following three factors:

a) Nature of the road.

b) Nature of the traffic on road.
c) Number of trains passing over the level crossing

Based on above factors, level crossings have been classified into following five categories:

a) Special class: where traffic is exceptionally heavy.

b) ‘A’ class: Level crossing on grand trunk roads.
c) ‘B’ class: Level crossing for metalled roads.
d) ‘C’ class: Level crossing for unmetalled roads.
e) ‘D’ class: Cattle ramps used for cattle and pedestrians only.

Equipments in stations and yards

Necessity of equipment:

1. Equipment for the convenience of passengers in a passenger yard

For this purpose, public telephones, microphones, over-bridges or sub-ways etc. are provided
on busy-stations.

2. Equipment for goods services in a good yard

For this purpose, cranes, weigh-bridges, loading gauges and loading ramps, signals etc. are
provided

3. Equipment for the locomotives in Loco-yard

For this purpose, Engine sheds, ash-pits, ash-pans, examination pits, water columns, triangle,
turn-table are provided.

4. Equipment for the safety of traffic movements

For this purpose, buffer stops, scotch block, track junctions and signals may be provided.
 5. Other equipment of railways

Such as refrigerators, first-aid, over-head tanks, adequate water supply facilities, etc. are
provided.

Water columns

Water columns are provided for feeding the water to stream locomotives. They are provided
at intermediate stations by the side of the main line tracks at distances not less than 48 km. They may
also be installed on the ash-pits. At important stations two or more water columns can be provided.
They are also provided in locomotives yards.

The various component part of a water column is shown in Figure. They are fixed in ground
in the shape of an inverted ‘L’. The water is supplied to water column through an over- head tank. A
water column consists of a vertical pipe with a swivelling arm of either a horizontal or swan neck
shape. This horizontal pipe can be rotated in a horizontal plane around the vertical pipe. The foot
value is provided to regulate the flow of water in the column. The bag hose is adjusted to direct the
water to fall into the water tank of locomotive. The height of water column above the ground is kept
4.42 m and its projection from vertical pipe is 2.25m.

Turn-Table

A turn-table is also used for changing the direction the direction of locomotive like triangle.
The use of turn-table is made at important stations where available space is limited. A turn-table is a
costlier installation than a triangle.

The turn-table consists of a track on a platform which in turn is supported on a pair of girders.
The girders are properly braced and are supported on a central pivot. This circular platform of turn-
table is installed in a circular pit. Two or more tracks radiate from the circular edge of the pit. These
radiating tracks and track laid on the turn-table are kept at the same level. Locking-bolts are provided
for regulating the movement of turn-table.
Working principle of the turn-table:

The working principle of turn-table is as follows:

a) When an engine is to be turned, the turn-table is rotated about its pivot till the track on turn-
table is in the line of track on which engine is standing.

b) At this position, turn-table is locked by means of bolts, and the engine comes on to the turn-
table.

c) The bolts are removed and turn-table rotated till the track on table comes in the line of track
on which the engine is to be sent or diverted. This turn-table is rotated either by power or
manually.

Essentials of a turn-table

The various essentials of a turn table are:

a) The centre of gravity of the engine should directly fall on the pivot. In past, when the engines
were not heavy one-point support on pivot was enough to balance the load, but at present with
heavy engines three-point support is used in India. Three points of support consist of one
pivot and two points at the two ends of the turn-table girders with flangeless wheels.

b) The central bearing is of disc type for light engines and of the roller type for heavy engines.

c) The bottom of the pit is sloped towards a point near the centre from where the rain water is
carried away through sump and drain arrangement.

d) The diameter of the turn-table should be long enough to accommodate the longest engine. In
India, 19.8m length (or diameter) of turn-table is common, whereas in some cases, a length of
25.9m is also used for turntables.

e) Periodical painting of various parts of turn-table should be done as the turn-table is likely to
get corroded, due to action of water and steam from engines.

f) The circle on race-rail should be maintained in perfect level.

Fouling Marks

Fouling marks are the points fixed between a pair of converging tracks, to indicate a foul or
possibility of collision of vehicles beyond these points. Generally, side collisions are possible on the
turnout portion, when vehicles are standing on the turnout and other vehicle is moving on the
adjoining track. So fouling marks are provided as a measure against the possibility of such collisions
between the wagons.

Essentials of fouling marks:

The following are the essentials of fouling marks:

a) Fouling marks are provided between a pair of converging tracks. They should be firmly fixed
in the ground at right angles to the direction of track.

b) For economy, old sleepers or stone slabs or concrete slabs are used for making fouling marks.

c) To make the fouling marks prominent, they are either white-washed, or painted in white or
colour. The letters F and M should be clearly marked to indicate fouling mark.

d) Indian standards specify that fouling marks should be provided when the minimum distances
between centres of tracks are 4.27m for B.G., and 3.8m for M.G. and 3.66 for N.G.

e) The fouling marks should be laid in the line of top level of ballast section.

The position of fouling mark and its details are shown in figure:

Buffer stops

Usually, the dead end of a siding or the end of any track of terminal station is not kept bare but a
form of stop or barrier is provided at the end of the track, to prevent the vehicles, from running off
the track. This stop or barrier provided at the end, across the track of a siding or at terminal station is
known as “Buffer stop”. The important requirements of a buffer stop are:

a) The form of buffer stop should be strong enough to sustain the possible impact of a rolling
vehicle.

b) It should be clearly visible from a considerable distance.

c) A buffer disc or buffing beam with a cross-sleeper, painted in red colour, should be provided.

d) A red lamp at the centre of buffer stop should be provided for indication of the same at night.

A buffer stop consists of a buffing beam held in position by vertical posts and fixed to the track.
Sometimes, buffer stops are made with sleepers in the form of a box and earth filling is done inside
the box. The buffing beams are fixed at the level of buffers of the vehicles. The beams and vertical
posts are strengthened by struts.