Location of Signals

Considerations for Location 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 1Signal 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 ABlock Overlap For 2 Aspect Signals Route of LSS of Stn ABlock Overlap For Multi-Aspect Signals Station A Station B Portion to be kept clear for giving line clear by Stn B

For 2 Aspect Signals For Multi-Aspect Signals

Main Line Loop Line Not 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 –Router Departure signals (GR 3.10): –Starter –Advanced Starter

Signals at Stations Multiple Aspect Signals: Reception Signals: –Distant –Inner distant –Routing –Home Despatch Signals: –Starter –Advanced Starter GR 3.07 (6) covers the provision of 2 Distant Signals. DistIdistH YYYR YYYYY(LL) GYYY(ML) GGG

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 1 st Facing Point (Clear of Lock Bar) or FM (if the 1 st point is a trailing point) –If located more than 180 m from the 1 st 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 1 st 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 1 st FP or BSLB (if 1 st 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

Typical layout using LQ signals

Typical layout using UQ signals

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