CTC Systems – Centralised Traffic Control on Indian Railways
1. What is CTC?
Centralised Traffic Control (CTC) is a modern relay & micro-processor based signalling system that enables a single controller to remotely operate points & signals over a large territorial section from one location, thus converting “block working” into “direct working with continuous train movement authority”.
2. Technical Architecture
| Sub-System | Function | Typical Medium |
|---|---|---|
| Central Control Unit (OCC) | Train despatching, route setting | LAN / OFC |
| Station Terminal Unit (STU) | Local interlocking execution | Copper quad / E1 |
| Track-side Equipment | Point machine, LED signals, axle-counter | Dedicated cable / OFC |
| Communication Link | Redundant 2 Mbps OFC ring | STM-1/4 SDH |
| Back-up Mode | Panel with slides / emergency local panel | — |
- Safety Integrity Level (SIL-4) – CENELEC 50128/50129
- Response time ≤ 1.5 s (command to signal aspect change)
- Availability target ≥ 99.97 % (Indian Railway spec: IRS: S-99/2017)
3. Historical Milestones
| Year | Event |
|---|---|
| 1927 | First CTC on Nagpur–Asansol freight section (GIPR) – 140 km |
| 1959 | All-India panel commissioned at Asansol with 60 km control stretch |
| 1987 | Electronic Route Relay Interlocking (RRI) interfaced with CTC at Itarsi |
| 2003 | Mumbai Central–Virar (60 km) – first COLOUR-LIGHT CTC on WR |
| 2012 | Ghoti–Igatpuri (58 km) – first OFC-based CTC under MRSS project |
| 2019 | Kharagpur–Bokaro Steel City (267 km) – longest contiguous CTC commissioned |
| 2022 | “One-Click CTC” – cloud-based GUI launched by CRIS for SECR |
4. Current Status (2023-24)
- Total route km under CTC: ≈ 6 800 km (≈ 11 % of IR network)
- Zonal topper: South East Central Railway – 1 420 km
- Ongoing works:
– Bhopal–Itarsi–Nagpur 3rd line (412 km) – target 03/2025
– Vijayawada–Gudur 4th line (455 km) – integrated with AFTC & TASS - Budget allocation 2023-24: ₹ 2 940 Cr under SS-2025 (Signal & Telecom)
- Mission 2030 target: 25 000 km to be brought under CTC / MMLS
5. Benefits & Features
✅ Increases sectional capacity by 15-25 % without new track
✅ Eliminates physical token / paper authority – only “continuous authority”
✅ Supports 160 km/h operation with Automatic Block Signalling (ABS) overlay
✅ Integrated with FOIS & TMS – real-time train plotting
✅ Energy saving – 8-12 % traction power due to reduced idling
6. Key Standards & Documents
- IRS:S-99/2017 – “Specification for Centralised Traffic Control”
- IRS:S-51 – Route Relay Interlocking compatibility
- RDSO/SPN/177/2019 – Axle-counter interface
- CENELEC EN-50128/50129 – Software safety
7. Frequently Asked Facts (Memory Capsule)
- First CTC section in Independent India: Asansol–Sitarampur (1959)
- Longest CTC section: Kharagpur–Bokaro (267 km)
- First zonal HQ with CTC back-up: Bilaspur (SECR) – 2020
- Maximum number of stations controlled from one panel: 61 (Howrah–Barddhaman, ER)
- Minimum distance between two CTC controlled stations: 5 km (Borivali–Goregaon, WR)
- CTC + Automatic Train Protection (ETCS-2) pilot: Godhra–Vadodara (66 km) – 2023
8. 15+ MCQs – CTC Systems
1. Which Indian Railway section was the first to be equipped with CTC technology?
Answer: Nagpur–Asansol (1927)
2. CTC achieves its safety standard as per which SIL level?
Answer: SIL-4
3. What is the targeted availability of a CTC system as per IRS:S-99/2017?
Answer: ≥ 99.97 %
4. The longest contiguous CTC section (267 km) is situated on which division?
Answer: Kharagpur division of SER
5. Which communication medium is primarily used for modern CTC networks?
Answer: Redundant 2 Mbps OFC ring
6. CTC increases line capacity by approximately how much percent?
Answer: 15-25 %
7. The first colour-light CTC in India was commissioned between which stations?
Answer: Mumbai Central–Virar (2003)
8. Which zone leads in CTC route kilometre as on 31.03.2023?
Answer: South East Central Railway (SECR)
9. What is the maximum permissible speed on a CTC section with ABS overlay?
Answer: 160 km/h
10. Which organisation has developed the “One-Click CTC” cloud-based GUI?
Answer: CRIS
11. The response time (command to aspect change) in CTC shall not exceed:
Answer: 1.5 seconds
12. CTC converts “block working” into which type of working?
Answer: Direct working with continuous authority
13. Which specification governs the software safety requirement of CTC?
Answer: CENELEC EN-50128/50129
14. The 2023-24 budget allocation for signalling works (including CTC) under SS-2025 is:
Answer: ₹ 2 940 crore
15. Mission 2030 envisages bringing how much route km under CTC / MMLS?
Answer: 25 000 km
16. CTC integrated with which freight system provides real-time train plotting?
Answer: FOIS (Freight Operations Information System)
17. The pilot section where CTC is being integrated with ETCS-2 ATP is:
Answer: Godhra–Vadodara (WR)
Revision Tip: Remember “C-3” – CTC gives Continuous authority, increases Capacity by ~20 %, and is Controlled from one office.
BETA
