Signals on Railway

Railway Signaling: Introduction to Signals, Objective of signals. Types of Signals, Operating Characteristics, Functional Characteristics, Locational Characteristics, Special Characterstics

1. SIGNALS O N RAILWAY PREPARED BY: SATYAPAL SINGH ASSISTANT PROFESSOR CIVIL ENGINEERING DEPARTMENT BADDI UNIVERSITY

2. INTRODUCTION Signalling is the system used to control trains traffic safely and it prevents trains from colliding. Signals consists of systems, devices and means by which trains are operated efficiently and tracks are used to maximum extent and thus maintaining the safety of the passengers. Points, instruments and other equipment are involved for the use and working of signals.

3. OBJECTIVE OF SIGNALS To ensure the safety between two or more trains which crosses or approaches each other’s path. To provide facilities for the maximum utility of the track. To provide facilities for the maximum utility of the track. To guide the trains movements during maintenance and repair of track. To safeguard the trains at converging junctions and give directional indications at diverging junctions.

4. TYPES OF SIGNALS OPERATING CHARACTERSTICS A) Detonating Signals B) Hand Signals C) Fixed Signals FUNCTIONAL CHARACTERSTICS Semaphore Type Signals B) Warner Signals C) Shunting Signals D) Colored Light Signals LOCATIONAL CHARACTERSTICS Reception Signals B) Departure Signals SPECIAL CHARACTERSTICS Repeater or Co-acting signals B) Routing Signals C) Calling on Signals D) Point Indicators E) Modified Lower Quadrant Semaphore Signals F) Miscellaneous Signals

5. OPERATING CHARACTERSTICS FOG/AUDIBLE OR DETONATING SIGNALS These are used when hand signals or fixed signals are not visible due to foggy condition. Detonators are placed on rails which exploded with a loud sound when the train passes over them. This sound draws attention to the driver about closeness of signals. These signals consists of containers with explosives and are fixed on the rails by means of clips. From safety point of view, 3-4 detonators must be placed on the rail about 10-15 metres interval at 400-500 metres ahead of signals to enable the drivers to stop the train or follow the signal.

6. OPERATING CHARACTERSTICS FOG/AUDIBLE OR DETONATING SIGNALS These signals are also used during emergencies like derailment, accidents etc.

7. OPERATING CHARACTERSTICS B) HAND SIGNALS These are given either by flag fixed to a wooden handle or by the guard holding coloured flags or by bare arms. During night time, kerosene lamps fixed are used in which moveable glass slides of green, red and yellow shades are used. These signals are generally used by guards, station master, cabin man, key man, point man or any other authorised person.

8. OPERATING CHARACTERSTICS C) FIXED SIGNALS These are usually of semaphore type and usually fixed at a place. The mechanism of this type of signal is so arranged that in normal position, it indicates the stop position.

9. FUNCTIONAL CHARACTERSTICS SEMAPHORE/STOP SIGNALS It consists of a vertical post on which a moveable arm is pivoted at the top. The arm can be kept horizontal or can be inclined at 45 degree to horizontal. The outer end of the arm is 2.45 cm broader than that at post. It is controlled by means of levers and cables from the cabin. The spectacles of red and green are fixed in the arm. These are fixed on the left hand side of the track with spectacles towards driver. The signal mechanism is so arranged that it shows the stop position to the driver.

10. FUNCTIONAL CHARACTERSTICS SEMAPHORE/STOP SIGNALS: In picture 1, horizontal arm indicates “DANGER-STOP” and in the inclined arm indicates “CLEAR-PROCEED”. In daytime, position of arm indicates the signal but during night-time, light of lamp passing through spectacle gives the signal. The functions of semaphore signal are shown in picture 2.

11. FUNCTIONAL CHARACTERSTICS B) WARNER SIGNALS: A semaphore signal at the entrance to the station combines with a warner signal. Warner signal is similar to semaphore signal except v-notch at free end that is moveable arm is fish tailed as shown. Warner signal is placed at the same post of semaphore signal at 1.8 to 2.1 m below the semaphore signal. Warner signal is painted “YELLOW” and exhibit a yellow or amber light instead of red colour.

12. FUNCTIONAL CHARACTERSTICS C) SHUNTING SIGNALS: It is also known as “disc or ground” signals. These signals are used in shunting operations at station yards. It consists of a circular disc with red band on white background. Two holes are provided. One for red lamp and another for green. When red band of disc is in horizontal position or it shows red light, it indicates “STOP”. When red band is at inclined position at 45 degrees or it shows green light, it indicates “PROCEED”.

13. FUNCTIONAL CHARACTERSTICS D) COLOURED LIGHT SIGNALS: With the introduction of electric traction, to meet increased traffic requirements, semaphore signals were being replaced by coloured light signals. They may be either Two aspects (red or green) Three aspects (red, yellow, green) Four aspects (green, yellow, red and yellow) Five aspects with additional aspect of yellow over green.

14. LOCATIONAL CHARACTERSTICS RECEPTION SIGNALS: The signals which control the reception of trains into a station is known as “Reception Signals”. It is of two types: Outer Signals Home Signals

15. LOCATIONAL CHARACTERSTICS Outer Signal: Outer signal is the first warner signal which is provided at this distance beyond the station limit. is the first stop signal at a section which seen by the loco-pilot. Trains moving at high speed requires certain distance for stopping. Hence, the loco-pilot get aware about the position in advance that platform is clear or not. This gives the position of stop signal ahead.

16. LOCATIONAL CHARACTERSTICS b) Home Signals: Due to the location at the door of station, it is termed as “Home Signal” . It is the next signal after outer signal towards station. It is the signal that indicates whether platform is clear or not. Home signal has the bracketed arms to indicates which line is to be used. Its main function is to protect the station. Therefore, maximum unprotected distance between the signal and the point is 180 metres due to its location at door of station.

17. LOCATIONAL CHARACTERSTICS B) DEPARTURE SIGNALS: Those signals which controls the departure of trains from the stations are known as “departure signals”. These are mainly of two types: Starter signals Advanced starter signals

18. LOCATIONAL CHARACTERSTICS Starter Signals: This signal is provided at the forward end of platform which controls the movement of the train as they leave the station. It gives the permission to the trains as they left the station. It gives the permission to the trains to leave the platform for the next station. No train can leave the platform until or unless this signal is lowered, that’s why it is known as “Starter S ignal”. If advanced starter signal is not provided then in such cases, starter signal has to be placed all the connections of the line to which it refers unless permitted by approved instructions.

19. LOCATIONAL CHARACTERSTICS b) Advanced Starter Signal: The limit of station section lies in between home signal and advanced starter signal. The signal which allows the train to enter in block section is called as “Advanced Starter Signal”. The advanced starter signal is generally becomes the last stop signal where it is provided. It is an indication for the train having left the station and is no more the responsibility of the station master. These signals are provided at 180 metres or more beyond the last point or switches.

20. SPECIAL CHARACTERSTICS REPEATING OR CO-ACTING SIGNALS: Generally when a train passes through a station without stopping, it comes across 5 signals: WARNER, OUTER, HOME, STARTER AND ADVANCED STARTER SIGNAL . But when driver’s vision obstructed by An over-bridge between the signals A sharp curvature in the alignment A signal is provided with the duplicate arm of smaller size to repeat the information at some points. Such signals are known as “Repeating or Co-acting Signals”.

21. SPECIAL CHARACTERSTICS B) ROUTING SIGNALS: At big station, where number of lines exists at the station taking off different routes from main line, besides one main Home signal, Routing signals are provided at diversions. This  signal used to indicate to a Loco Pilot which of two or more diverging routes is set for him, when the Home signal is, in consequence of its position, inconvenient for this purpose .

22. SPECIAL CHARACTERSTICS C) CALLING ON SIGNAL: These signals are similar to semaphore signal but they are smaller in size and are fixed on the same post below the main signals. When a train stops with the Home signal indication, then a Calling-On signal permits a train to proceeds by cautiously by keeping the signal arm as “PROCEED” These signals are very helpful when repair work is going on. Even if the calling on signal is at “OFF” position, driver should be prepared to stop the train at any moment if required.

23. SPECIAL CHARACTERSTICS D) POINT INDICATORS: These are used to indicate the route to driver as a precautions to against bursting of points or running into an occupied line when signals are not available for this purpose. These points are used to protect the yard onto a running line.

24. SPECIAL CHARACTERSTICS E) MODIFIED LOWER QUADRANT SIGNALLING Two-position semaphore signaling  employing yellow distant signals is known as "modified lower quadrant signaling". A yellow distant arm is never placed on the same post as a stop signal, a red warner arm being provided in its place where necessary .

25. SPECIAL CHARACTERSTICS F) MISCELLENEOUS SIGNALS: Cautionary Signals/ Cautionary indicators: When the track is under repair, the driver should be cautious to reduce the speed and be prepared to stop at any moment. b) Stop Indicators: This indicates the driver to stop the train at once. c) Speed Indicators: This indicates the driver to drive the train at indicating speed.

26. SPECIAL CHARACTERSTICS F) MISCELLENEOUS SIGNALS: d) Shunting Indicators: These indicators marks the limit of shunting operations. e) Terminal Indicators: This indicator shows that driver can resume to normal speed. Some other Indicators: