Location of Signals

Considerations forLocation of Signals

• Braking Distance

• Overlaps

• Isolation

• Simultaneous Reception

Overlaps

- block overlap

- signal overlap

Adequate distance

• As per GR 1.02 (2), Adequate Distance means the distance sufficient to ensure safety.

• This is the length of track in advance of a signal which must be kept clear before the signal next in rear can be taken off.

For taking off Signal 1, portion shown beyond Signal 2 must also be clear. This portion is the Adequate Distance.

Signal 1 Signal 2

Adequate distance

We can therefore say that:

• A Stop Signal shall not display Off aspect unless the line is clear not only upto the next (stop) signal but also an adequate distance beyond it.

Important:This condition does not apply for Home signal at terminal stations and also if the train has been brought to a stop outside the home signal.

Adequate distance

In other words,

The length of track in advance of a stop signal, which should be kept clear before the (stop) signal next in rear can be taken off is known as adequate distance.

Adequate distance - how much?

• GR 3.40 dealing with conditions for taking off Home Signal lays down in sub-para (c) that the adequate distance shall not be less than 180 metres for 2 Aspect signals and not less than 120 metres for multiple aspect or MLQ signals.

• GR 8.01 read with GR 3.42 dealing with conditions for taking off LSS lays down in sub-para (2) that the adequate distance shall not be less than 400 metres for 2 Aspect signals and not less than 180 metres for multiple aspect or MLQ signals

• GR 9.01 dealing with automatic signals in sub-para (2) lays down that

the adequate distance shall not be less than 120 metres.

Overlap

• The adequate distance in advance of FSS of next station (for taking off LSS) is called Block Overlap, and is 400m and 180 m respectively for 2 aspect and multi-aspect or MLQ signals.

• The adequate distance in advance of Home Signal at a ‘C’ class station (for taking off LSS at station in rear) is always 400m for 2 aspect as well as for multi-aspect and MLQ signals.

• The adequate distance for taking off all other signals is called Signal Overlap, and is 180m and 120 m respectively for 2 aspect and multi-aspect or MLQ signals.

Overlap

• For taking off Home signal for reception on loop lines, overlap may be provided:

– either by providing a dead end siding of 180/120 metres, or

– by providing a sand hump or a snag dead end, or

– by setting the points for the main line.

• GR 5.19 (2) A sand hump or a snag dead end shall not be obstructed for any purpose and when it has become obstructed, it shall cease to be a substitute for the adequate distance for the purpose of taking ‘off’ signals.

Route of LSS of Stn A Block Overlap

For 2 Aspect Signals

Route of LSS of Stn A Block Overlap

For Multi-Aspect Signals

Station A

Station A

Station B

Station B

Portion to be kept clear for giving line clear by Stn B

Portion to be kept clear for giving line clear by Stn B

For 2 Aspect Signals

For Multi-Aspect Signals

Main Line

Loop LineNot for stabling

Isolation & Simultaneous Reception

Isolation: Definition

• Isolation means a condition in which a line is separated from all adjoining lines in such manner that it cannot be fouled by any movement taking place on the adjoining lines.

Isolation: Requirements

GR 4.11 Limits of speeds while running through stations -

(1) No train shall run through an interlocked station at a speed exceeding 50 kmph ... unless the line on which the train is to run has been isolated from all other lines by the setting of points … and interlocking is such as to maintain this condition during the passage of the train.

(2) In every case in which trains are permitted to run through on a non-isolated line, all shunting shall be stopped and no vehicle unattached to an engine or not properly secured in accordance with Rule 5.23 may be kept standing on a connected line which is not isolated from the through line.

Isolation: Requirements

• Exception to GR 4.11 is made at running junctions, where two block section lines meet at the same end of a station, equipped with full complement of signals.

• Where track circuits or other appliances have been provided to check that non-isolated lines are clear or occupied and the signalling is such that it is possible to give a distinct indication to the driver, then physical isolation may be dispensed with.

Isolation: Requirements

Rules for the opening of a Railway for the public carriage of passengers lay down vide Chapter VIII (Part III) contd. :

• Goods running lines may not be isolated from each other. (item 5)

• Isolation may be accomplished by connection to another line or long siding, by providing short dead end sidings or by providing traps. (item 6)

Isolation: Implementation

Main Line NOT Isolated from Line 1;

Hence run through speed cannot exceed 50 KMPH

Line 1

Line 2 (Main Line)

Line 3

Isolation: Implementation

Main Line Isolated from Line 1 & 3;

Hence run through speed can exceed 50 KMPH

Line 1

Line 2 (Main Line)

Line 3

Simultaneous Reception

Line 1

Line 2 (Main Line)

Line 3

Simultaneous Reception

Line 1

Line 2 (Main Line)

Line 3

UNIDIRECTIONAL

Simultaneous Reception

Line 1

Line 2 (Main Line)

Line 3

Line 1

Line 2 (Main Line)

Line 3

UNIVERSAL

Simultaneous Reception

Typical Yard Layouts &

Location of Signals

Signals at Stations

• LQ – 2 Aspect:Reception signals (GR 3.09):– Outer– Home– RouterDeparture signals (GR 3.10):– Starter – Advanced Starter

Signals at Stations

• Multiple Aspect Signals:Reception Signals:– Distant– Inner distant– Routing – HomeDespatch Signals:– Starter– Advanced Starter

GR 3.07 (6) covers the provision of 2 Distant Signals.

Dist Idist H

YY Y R

YY YY Y(LL)

G YY Y(ML)

G G G

Location of Signals – 2 Asp

• Warner:– On a post by itself at >= 1200 Mtrs in rear of

the FSS or Gate Signal to which it refers to– On the same post as and below “Outer”– On the same post as and below LSS

Location of Signals – 2 Asp

• Outer:– Will be the FSS where provided

– At >= 400 mtrs in rear of the point upto which the line may be obstructed after granting LC

– On Single Line – 580 mtrs in rear of Home• So that in addition to BO, SO for opposite Home is available

for simultaneous LC for this direction and clearance of opposite Home is possible

• Shunting facility till Adv Str or SLB is available

– On Double Line – 400 m in rear of Home

Location of Signals – 2 Asp

• Home– In rear of all connections– Close to 1st Facing Point (Clear of Lock Bar) or

FM (if the 1st point is a trailing point)– If located more than 180 m from the 1st FP,

other means of route holding eg LRB or TC to be provided

– For diverging lines – Bracketted Home (ML Home at higher level)

Location of Signals – 2 Asp

• Routing Signal &

• Intermediate Starter– Must be placed in rear of the points which it

protects (Like Home)

Location of Signals – 2 Asp

• Starter Signal– Placed at >= 400 m in advance of Home– Where provided for each converging line, it

should be so placed as to protect adjacent lines– Where only one starter used for 2 or more

converging lines, it should be placed outside the connections of the lines

Location of Signals – 2 Asp

• Advance Starter– Placed outside all connections of the lines to which it

applies

– On Single line >= 180 m from the outermost Point (to cater for SO of the Home)

– On Double Line >= 180 m from the Starter (SO of Home reckoned from Starter in DL)

– Where frequent shunting involved on ML, it may be placed at full train length beyond the Trailing Pt, provided Starter to Adv Str is TC

Location of Signals – Multi Asp

• Distant– Placed at NBD (Not less than 1 KM) from the

FSS or Gate Signal

Location of Signals – Multi Asp

• Home– At NBD in rear of next stop Signal where

provided– 180 m in rear of the point upto which line may

be obstructed after granting LC

Multi Asp – Home contd…

• Home– On Single Line – 300 m in rear of the 1st FP

• So that in addition to BO, SO for opposite Home is available for simultaneous LC for this direction and clearance of opposite Home is possible

• Shunting facility till Adv Str or SLB is available

– On Double Line – 180 m in rear of the 1st FP or BSLB (if 1st point is Trailing)

– Route Holding by LRB or TC

– For Diverging Lines – Bracketted Home (ML – Higher)

Location of Signals – Multi Asp

• Routing Signal

• Starter Signal• Intermediate Starter

Same Provisions

as in 2 Asp

Location of Signals – Multi Asp

• Advance Starter (Same as in 2 Asp)– Placed outside all connections of the lines to which it

applies

– On Single line >= 120 m from the outermost Point (to cater for SO of the Home)

– On Double Line >= 120 m from the Starter (SO of Home reckoned from Starter in DL)

– Where frequent shunting involved on ML, it may be placed at full train length beyond the Trailing Pt, provided Starter to Adv Str is TC

Y

Y

Y

Y

Typical layout using LQ signals

Typical layout using UQ signals

Typical layout using UQ signals

Thank You