Railway Signals

Railway Signal System

1. Unit 3- Signalling and Interlocking Objective- To provide facilities for the maximum utility of the track with safety as the prime concern.

2. Classification of Signals Based on operational characteristics Detonating (during foggy or cloudy weather where other signals are visible) Hand (flags/ lamps) Fixed Based on Functiona l characteristics Stop/Semaphore Warner (1 st signal for a station) Shunting (disc/ground) Coloured

3. Signals

4. Classification of Signals 3. Based on Locational characteristics Reception ( outer (1 st stop signal)/ home ) Departure ( starter (last stop signal)/ advance starter (if provided becomes last stop signal) 4. Based on Special characteristics Repeater (co-acting, when driver’s vision is obstructed by like overbridge ) Routing Point indicators Calling on signals (to proceed cautiously during repair works) Sequence of signals: warner(1st)-outer-home-starter-advance starter (last). Block section- distance between last and 1 st stop signal.

5. Signals

6. Control Systems Controlling the movement of trains while focusing on three aspects- Safety Speed Traffic density

7. Types Control Systems Absolute block / space interval/lock and block system (telephonic conversation between controller of control room and station masters of block stations to issue tokens as authority to enter block sections)

8. Types of Control Systems 2. Centralised traffic control system (centralization of operations using illuminated track diagrams)

9. Types Control Systems 3.Automatic train control system (electric track circuiting which alarms the driver through a siren for any danger)

10. Interlocking of tracks Principles- To set and lock the points and signals properly for an approaching train against the feasibility of conflicting movements i.e route should be clear of any obstructions for that particular train movement.

11. Types of interlocking Mechanical Electro-mechanical

12. Types of interlocking 3. Route-Relay 4. Electronic

13. Mechanical/ electrical consists of Stretcher bar Treadle bar Lock bar and tappet arrangements Connecting devices (rods, cranks, etc ) Temperature compensators

14. High speed track (speed>= 120kmph)

15. Included parameters LWR (long welded rails)/CWR (continuously welded rails)– this actually reduces number of joints which eventually increases service life of rails as less defects and failures will be there then) Diesel and electric traction Wider , correct and uniform gauge Proper alignment and high sleeper density Automation in train control operation through efficient signaling (in-cab signaling where track and train communicate to each other) Better suspension of rolling stock (vehicles over railway track) Modified locomotives and coaches Dynamic forces and fencing to tracks

16. Track tolerances Service tolerances (gauge variations on straight vis a vis curve track, alignment variations, uneven-ness, etc.) Safety tolerances Speed restrictions Loading and construction gauge (Loading gauge+ some clearance to pass through tunnels and under bridges)

17. Loading gauge

18. Assessment of track Qualitative (through visual inspection) Quantitative ( using track recording equipments ) Track recording car Hallade track recorder Rail flaw detector

19. Urban Railway System Tram (currently in Kolkata only) Sub-urban (EMU) Rapid transit system/Metro Monorail (Speed and route distance restrictions) Skyway

20. Other terminologies Turntable Triangle