Communication Based Train Control

Navneet KaushikDMRC

DMRC’s mission• Complete the Metro project without cost and

time over run• Catch up with the state of art technology• Started Metro operation in 2002 in Delhi with

track circuit based CATC (first time in India)• Decided to go for CBTC for Phase III on two

independent lines in 2012 – around 90 Kms• Also decided UTO on these lines (again first time

in India)

City Line Length Stations Headway Operation Traction SIG Supplier

Delhi Line-7 58 KM 38 90sec GoA4 25KV AC Bombardier

Delhi Line-8 38 KM 25 90 sec GoA4 25KV AC Nippon Signal

KOCHI 26 KM 22 90 sec GoA2 750V DC Alstom

Noida-Greater Noida

29 KM 21 90 sec GoA2 25KV AC Tender yet to be awarded

Scenario in the country:Apart from these, other CBTC projects in pipe line are Hyderabad, Lucknow, Vijaywada, Vizag, Nagpur, Ahemedabad, Kolkata and Mumbai

CBTC projects being executed by DMRC

DELHI METRO MAP INCLUDING PHASE III

Need for improvementKey challenges faced today

• increasing traffic, • absolute passenger safety and security, • travel comfort demands, • real time multimedia information and

entertainment in stations or in train• Operations need dynamically adjustable systems

while maintaining Safety and security• Energy efficiency

Solution – Communication at the core

Signalling draws its strength from efficient computing and Telecom

Signalling & Telecommunication are coming closure• to deliver a safer, efficient and passenger friendly

Rail Transport system • to give quick response to dynamics

Typically:Data backbones on Metro Rail– from 100 Mbps to 10 Gbps nowLink between train to wayside – wi fi to LTE in future

Two different applications1. Signalling and Train control – the vital one• low bandwidth (below 100 kbps) but high availability

(at least 99.99%), • highly robust and reliable • CBTC (Communication Based Train Control) for metros

or ETCS (European Train Control System) for mainline trains.

2. Passenger Information, maintenance, video surveillance, CCTV, internet access – the non vital one

• much higher bandwidth (train-to-ground and ground-to-train),

• lesser robustness can be accepted

Progress on Signalling front – Telecom upgrade automatic

No ATC Train stop Speed code Distance To Go Moving Block

TRAIN CONTROL

Mechanical Relay based Electronic

INTERLOCKING

Track circuit Axle counter Radio based (CBTC)TRACK VACANCY DETECTION

Definition of CBTC as per IEEE 1474 standard

• CBTC system is a "continuous, automatic train control system utilizing high-resolution train location determination, independent of track circuits; continuous, high-capacity, bidirectional train-to-wayside data communications; and trainborne and wayside processors capable of implementing Automatic Train Protection (ATP) functions, as well as optional Automatic Train Operation (ATO) and Automatic Train Supervision (ATS) functions."

Highlights of the definition• Location determination independent of track circuit • Continuous detection• High capacity train communication• Bidirectional train to wayside data communicationSolution – wifi radio working in ISM band taking

information from onboard ATP based on inputs from odometer, beacons etc. and transferring this information to track side ATP to calculate Movement Authority

2. The ONBOARD RADIO on train B transmits its position ( ) to the CBTC trackside equipment

5.The ONBOARD CBTC on train A calculates the safety curve and applies it to the train to be protected

CBTC Functionality – Normal Mode

TRACKSIDECBTC

TRACKSIDERadio

Controller

3. Trackside CBTC calculates the point to be protected ( ) ), by the tail of train B

4. The TRACKSIDE RADIO continuously transmits to the following train (A) the point to be protected ( ) )

RadioTrain

CBTCRadioTrain

CBTC

1. Based on the odometry, train B calculates continuously its position (and recalculates tolerances after passing over the track balises)

A B

Trackside Radio

Trackside Radio

Trackside Radio

A B

2. The interlocking continuously provides

information on the track circuits occupied to the

TRACKSIDE CBTC

5.The ONBOARD CBTC on train A calculates the safety curve using the point to be protected ( )

CBTC Functionality – Mixed Mode

TRACKSIDECBTC

TRACKSIDERadio

Controller

(NO-COMN)

3. Trackside CBTC knows at all times the existence of trains, and locates the point to be protected ( ) ) behind the last track section occupied by train B

4. The TRACKSIDE RADIO continuously transmits to the following train (A) the point to be protected ( )

RadioTrain

CBTC

1. A non-communicating train (B) does NOT transmit its position but occupies track section

A B

Trackside Radio

Trackside Radio

Trackside Radio

Interlocking

Advantages of CBTC

• Moving block instead of fixed block hence Optimized train speeds to gain best line capacity

• Ease of upgradation to Driverless system• Ease of maintenance;• Easy expansion;• Immunity against interference;• Ease of Obsolescence management;• Minimum trackside equipment.

Grade of Automation

Some considerations for design

• Fallback• Frequency availability and interference• UTO from day one or upgradation later• Overlap• Station layouts to match headways• PSD commands• And many more

Failure and Fallback

• In a CBTC system if the communications link with any of the trains is disrupted then corresponding parts of the system have to enter a failsafe state until the problem is rectified.

• Depending on the severity of the communication loss, this state can range from vehicles temporarily reducing speed, coming to a halt or operating in a degraded mode until communications are re-established.

• If duration of communication failure is permanent, contingency operation need to be implemented - Manual operation and absolute block

Fallback SignalingTo handle this situation or do operation in case of failure of primary train detection due to communication loss, simplest method is to guide the driver over phone about his movement authority. OR provide secondary means of train detection and resort to absolute block working with the help of signalsConsiderations:•Capital cost•Number of track side equipment - maintenance•Effect on operation•Mixed mode operation

Methodology adopted by DMRC

DELHI METRO RAIL PROJECT Phase-IV, Aerocity - IGNOU - Tughlakabad Corridor

Metro Bhawan, Barakhamba Road , New Delhi 110001.DELHI METRO RAIL CORPORATION LTD.

(To Lajpat Nagar)

(To & From Depot)

Frequency issues – ISM band

• World over wi-fi in ISM used• Mainly in 2.4 GHz band• Various techniques used to have reliable

communication (mostly proprietary) Main issues:• Jamming – during VIP movement• Congestion in 2.4 GHz band – where metro

going through thickly populated areas

Frequency issues – ISM band• Demand for CCTV from train is growing• So two frequency bands are needed – one for CBTC and one for

CCTV• 2.4 GHz already heavily utilized

– CBTC needs low throughput but highly stable and interference free

– Most of the vendors have proven CBTC products in 2.4 GHz• 5.8 GHz has limited bandwidth (WPC restriction) making it

unsuitable for CCTV• Allow wider band in 5.8 GHz • Preferably reserve a frequency band for railway

Upgradation to UTO later or straight away UTO implementation?

• Main requirements of UTO– Normal operation by onboard and track side computers

communicating continuously– Manual functions (in case of failure) to be done remotely

which requires a communication channel of sufficient bandwidth to deal with alarms and remote commands

• The basic requirement is full filled by CBTC by default• The investment in UTO is very low if decided initially

compared to upgradation later• Choice with operator if to use UTO as default mode of

operation

Overlap requirement

• Main line railway have requirement of signal overlap – Absolute block working

• CBTC implements moving block• Train always remain protected hence no need of

signal overlap • Signal overlap needed only in fallback (rare)• If provided, Moving Block not available for a

certain distance – un necessary gap created• Conscious decision required

Effect of overlap

Terminal layout

• Demand – improved headway• Signaling systems capable of providing• Layout of terminal stations and intermediate

turnback stations remain a bottleneck• Variety of layouts available• Need to decide in the beginning of project

PSD commands• Need for best end to end run time• Demand for PSD increasing for passenger protection

and more space on platform• Train door and PSD opening and closing time already

high (2.5 s and 3 s respectively)• Can’t afford delay in transfer of door open and close

command from Onboard to PSD at station – two paths– On board – zone control – station control (CBI) – PSD – On board – station control - PSD

• There are many more issues• If one really wish to get the best results from

CBTC, consider such issues in advance while planning

Thanks