TCAS Systems – Train Collision Avoidance System
1. What is TCAS?
TCAS (Train Collision Avoidance System) is an indigenous, GPS/GNSS-based, SIL-4 certified, automatic train protection (ATP) system developed by the Indian Railways to prevent Signal Passing at Danger (SPAD), over-speeding and collisions.
2. Technical Architecture
| Sub-system | Function | Key Parameters |
|---|---|---|
| On-Board Unit (OBU) | Continuous speed monitoring & automatic braking | 2-out-of-2 fail-safe architecture, SIL-4 |
| Radio Infrastructure | Data exchange between track & train | TETRA 800 MHz or LTE-R (4.9 GHz) |
| Track-Side RFID | Location reference at 500 m intervals | Passive tags, 512-bit memory |
| Brake Interface | Pneumatic / electro-pneumatic | 0-5 kg/cm² pressure, 3 s reaction time |
| HMI | Driver display & audible alerts | 5.7″ TFT, 24 pre-recorded voice messages |
- Safety Integrity Level: SIL-4 (10⁻⁹ dangerous failures/hour)
- Braking Intervention: Service brake @ 5 km/h above limit, Emergency brake @ 15 km/h above limit
- Location Accuracy: ≤ 2 m CEP (Circular Error Probable)
- Power Supply: 24 V DC (battery back-up 2 h)
3. Historical Milestones
| Year | Event |
|---|---|
| 2011 | RDSO conceptualises TCAS under “Zero-Accident Mission” |
| 2012 | Proof-of-concept trials on 50 km Sonenagar-Mughalsarai section |
| 2015 | SIL-4 certification by Independent Safety Assessor (ISA) – SNC Lavalin |
| 2016 | Production order for 200 locos; first fitment on WAG-9 #31006 |
| 2018 | TCAS rebranded as “Kavach” by Hon’ble MR; 1st commercial run on South Central Railway |
| 2022 | Kavach certified for 160 km/h operations; scope expanded to 2,000 route km |
| 2023 | Vision 2024 – 2,000 km + 44,000 km tender under PM-Gati Shakti; domestic IPR with HBL Power & Kernex Microsystems |
4. Current Status (as on 31-03-2024)
| Parameter | Achievement |
|---|---|
| Route covered | 1,465 km (SC-CR) + 535 km (WR) = 1,965 km |
| Locomotives fitted | 3,124 (WAG-9, WAP-7, WAP-5) |
| Stations | 139 stations with Radio Block Centre (RBC) |
| Speeds certified | 160 km/h (continuous), 200 km/h (design) |
| Made-in-India content | 96 % (under Atmanirbhar Bharat) |
| Cost | ₹ 34 lakh per loco, ₹ 1.5 cr per RBC |
| World Bank funding | USD 1.2 bn for 3,000 km ECR & NCR corridors |
Upcoming:
- Delhi-Mumbai & Delhi-Howrah corridors (3,000 km) by 2025
- Integration with ETCS Level-2 (dual-stack OBU)
- LTE-R spectrum (4.9 GHz) auction cleared by DoT
5. Quick-Fire Facts for MCQs
- TCAS works on distributed block principle – no central control.
- “Gate” mode switches off braking within 50 m of reception to allow shunting.
- “Shadow” memory stores last 30 days of logs (8 GB).
- RFID tags are passive – no battery.
- TETRA provides 3 km radio range in plain terrain.
- Kavach is the only ATP in the world that overlays existing signalling without track circuiting.
- GAPS (GPS Aided Protocol System) is the location engine inside OBU.
- Brake assurance test mandatory every 24 h; failure locks loco @ 10 km/h.
- RDSO spec No.: RDSO/SPN/201/2015 latest Rev-4.
- ISA – RAMS study (Reliability-Availability-Maintainability-Safety) mandatory.
6. 15+ Railway Exam MCQs
1. What is the Safety Integrity Level (SIL) of TCAS?
Answer: SIL-4
2. Which frequency band is used by TCAS for data communication?
Answer: 800 MHz TETRA (also accept 4.9 GHz LTE-R)
3. The indigenous TCAS has been branded as:
Answer: Kavach
4. TCAS prevents which of the following? (choose odd one out)
Answer: Hot-axle (others – SPAD, over-speed, collision – are prevented)
5. What is the emergency brake intervention speed threshold?
Answer: 15 km/h above permissible speed
6. RFID tags used in TCAS are:
Answer: Passive
7. Which organisation developed TCAS?
Answer: RDSO (Research Designs & Standards Organisation)
8. The maximum certified speed of Kavach as on 2024 is:
Answer: 160 km/h
9. Cost of fitting Kavach on a single locomotive is approximately:
Answer: ₹ 34 lakh
10. Which corridor was first to implement TCAS commercially?
Answer: South Central Railway (SC-CR)
11. TCAS OBU architecture is:
Answer: 2-out-of-2 fail-safe
12. The location accuracy required for TCAS is:
Answer: ≤ 2 m CEP
13. Under Vision 2024, Indian Railways aims to cover how many route km with Kavach?
Answer: 2,000 km immediately + 44,000 km subsequently
14. What is the battery back-up time for OBU in case of loco power failure?
Answer: 2 hours
15. Which of the following companies is NOT associated with Kavach production?
Answer: Alstom (HBL Power & Kernex are Indian partners)
16. The brake assurance test must be carried out every:
Answer: 24 hours
17. TCAS is based on which block system?
Answer: Distributed block system
Revise the figures & dates – they are favourite fodder for shift-1 vs shift-2 comparisons. All the best!
BETA
