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Anti-Collision Device (ACD) Network
(Raksha Kavach
TM
)
… A Train Collision Prevention System (TCPS)
Ajaykumar A. Bhatt, IRSSE
Chief Signal & Telecommunication Engineer
Konkan Railway Corporation Limited, India
International Railway Safety Conference Goa 2007

‘Anti-Collision Device (ACD) Network’ – Ajaykumar A. Bhatt, CSTE, Konkan Railway, India 2
Coverage
• Why ACD ?
• Expectations from ACD
• What is ‘ACD Network’ ?
• Installation of ACD Network
• Working of ‘ACD Network’
• ACD Implementation in India
ACD Network … A Train Collision Prevention System (TCPS)

Why Anti-Collision Device (ACD) needed ?
Railway operations today have a ‘limitation’ of ‘single point’
failure which is built in Driver’s human actions
• At Station – Driver’s failure to either ‘read correct aspect’ or
‘signal itself showing a wrong aspect’ can lead to a Collision!
• In Mid-section - Driver does not know in ‘advance’ whether –
– A Train is ahead on ‘same’ Track and ‘approaching’ his Train
– A Train is on ‘adjacent’ Track and infringing his Track, may be
after ‘derailing’ and/or ‘parting / jumbling’
– A ‘Non-Interlocked’ Level crossing Gate is in ‘open’ condition
Except what he can see ‘himself’ - to prevent a Collision!

‘Prompted’ Konkan Railway to Develop Anti-Collision Device in Aug 1999

Expectations from ‘ACD Network’
• Elimination of ‘Human Error’ (No User inputs for Operations)
• Design to be ‘Universally Acceptable’ on Railways, namely
– ‘Compatible’ with different types of Signaling systems
– ‘Adaptable’ in both ‘Diesel’ and ‘Electric’ Tractions
– ‘Workable’ in Single, Double & Multiple lines sections
– ‘Suitable’ for existing ‘Train Working Rules’
– No ‘positive’ indication to driver for Train Operations
– ‘Available’ for Train Collision Prevention ‘Globally’ whereas
decisions for braking taken ‘Locally’ (continue..)

Expectations from ‘ACD Network’ (contd..)
• Design to be ‘Universally Acceptable’ on Railways, namely
– ‘Maintainable’ (wireless communication, easy to install,
customize, configure, test, commission, repair/replace)
– No ‘track based’ inputs in mid-section
– Limited ‘point detection’ & ‘main line track circuits’ based
inputs at stations (for preventing collision with ‘stabled
train load’
– ‘Durable’ (Even when failure occurs the impact is local)
– ‘Reliable’ in operation (shall not fail to ‘automatically’
apply brakes when it is supposed to prevent collision and
shall not also ‘unnecessarily’ apply brakes)

ACD Network … A Train Collision Prevention System (TCPS)
What is ‘ACD Network’(Raksha KavachTM
) ?

‘ACD Network’ - Definition
•‘ACD Network’ is made of ‘self-acting’, computer based
radio communication devices called ‘Anti-Collision
Devices’ (ACDs)
• When Collision is perceived, it ‘automatically’ applies
brakes to Trains, thereby protecting the ‘Traveling Public’
from ‘dangerous’ Collision or minimizing the extent of
damages that may be caused due to a Collision
•It also ‘Warns’ Road Users ‘in advance’ of an approaching
Train at a Level Crossing.

BlockSch
em
aticof LocoA
CD
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ithA
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onsole
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lobal Positioning
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•ABU- AutoBrakingU
nit,
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icro-ProcessorBase
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adioT
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sceiver
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ataEn
try
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eyP
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aintenance]
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ow
er
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onverter
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utside
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otive, Cab
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ontrol
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(3Km
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isual A
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ABU
ACD
Installation of Loco ACD - Driver’s Cab – Diesel Loco
Driver’s Console

Loco ACD - Normal Working
Both the Trains travelling on their
respective lines in Block section –
No action by ACD
L 9 9 9 9 9
G 9 9 9 9 9 1 9 : 2 6
Driver’s Console
Self Loco ACD-ID
Self Guard ACD - ID Indian Standard Time
(GMT+ 0530 hrs)

‘Portable’ Guard ACD for Passenger Train
Size: 210 x 235 x 130 mm Weight: 6.02 Kg

Guard ACD fitted in Brake Van of Passenger Train

Portable Guard ACD placed on roof-top of Brake Van of a Freight Train
Remote ‘SOS’ of Guard (with Key Chain)

Station ACD
[Fitted at a Station & linked to Signalling circuits]
Size: 360 x 350 x 240 mm
Weight: 14 Kg
Size: 165 x 175 x 160 mm
Weight: 2 Kg

Station ACD - Normal Working
When no event is observed by Station ACD
– ‘AAAA’ represents the Station Code
A A A A S T N 1 9 : 2 6
Station Master’s Console
Station Code
(‘AAAA”)

Gate ACD (Manned Level Crossing )
[with Boom Locking Arrangement]
Size – 250x 270 x 110 mm, Weight - 5 Kg
Lifting Barrier
Close/Open
Sensing Switch
Boom Locking
Sensing Switch

Antenna
Solar Panel
Hooter& Flasher
Anti-theft
arrangement
Location Box
Tower – 12 m
Gate ACD
(Un-Manned LC)
Size – 250 x 270 x 110 mm
Weight - 5 Kg

ACD on a Train uses GPS for Location Determination
• Constellation of 27 [‘24’ + ‘3’ (spare)] Global Position System (GPS)
Satellites formed around the ‘Earth’
• ‘Four’ satellites needed to be in view of GPS Receiver
• Time Stamp (Date & GMT), and other data given by GPS Receiver using
‘Triangulation method’ per second, as under:
– Location (Latitude, Longitude)
– ‘Course Angle’ of Travel (w.r.t. to true ‘North’ of Earth), Basis
for identification of change of Track, by a Train
– Speed (in knots)

GPS Satellites
UHF Data
Radio Modem
GPS Receiver
Working of “on-board” ACDs
Receive inputs from satellites, communicate with each other using radio
modems & use intelligence to act – To prevent ‘dangerous’ Collisions
ACDs have Knowledge Embedded Intelligence
Inter-ACD Radio Communication
Loco
Loco

ACD Network mainly takes ‘Track-ID’ based decisions
Station Track-ID (TID) Plan (Stored in a ‘Station ACD’)
P3
P2
P17
P8
P24
P20
P22
TID=16
P26
P25
P23
P21
P19
P18
P12
P11
P7
P6
P4
P1
P5
TID=15
TID=17
TID=14
TID=18
Database of TID Plans of Stations, GPS shadow zones, Level Crossings and
Repeaters on ACD Routes are stored in memory of ‘Loco’ & ‘Guard’ ACDs

Deduction of Change in ‘Track-ID’ by Train bound ACDs - 1
On Points & Crossing – Deviation Count Theory (patented by KRCL)
• ‘Point Zone’ is defined between ‘A’ and ‘B’ on the track.
• Even with a location ‘inaccuracy’ of 25 metres, the Loco/Guard ACD will
not miss the beginning of ‘Point Zone’
• Inside the ‘Point Zone, ‘reversal’ of Angle of travel decides the change in
‘Track-ID’ of Loco ACD and Guard ACD, as the case may be.
5 m
25 m
25 m
‘Point Zone’ connecting ‘Main Line’ to ‘Loop Line’
No change in Angle
3 deg ‘change’ in angle
3 deg ‘Reversal’ of Angle
A (Lat, Lon)
TID = 15
TID = 16
B (Lat, Lon)

In case of negotiating a points and crossing zone where DCT is
‘non-workable’, the points position ( i.e. ‘Normal’ or
‘Reverse’ read from signaling circuits), radiated by Station
ACD would enable Loco ACD and Guard ACD to ‘auto-deduce’
the change of their ‘Track-ID’, after coming out of DPXZ.
On Dead Points & Crossing Zones (DPXZ) – where ‘DCT’ non workable
Signaling
Relay
Room
Station
ACD
TID = 15
TID = 16

Track-ID (TID) Assignment – While Leaving a Station – SINGLE LINE SECTION
TID = 15
TID = 16
T1
TID = 14
In case of Single line section, the ‘UNIQUE’ Track-ID of the
section would be forced on Loco ACD and Guard ACD of a train,
while leaving the Station

In case of Double line section, the ‘valid’ Track-ID of the
section would be communicated by Station ACD to Loco ACD
of train while leaving the Station, based on occupation of
‘two consecutive’ track circuits at dispatch end.
Track-ID (TID) Assignment – While Leaving a Station – DOUBLE LINES SECTION
TID = 15
TID = 16
T1
TID = 14
TID = 17
Track Ckts.
Track Ckts.

In case of Multiple lines section, two consecutive track
based RF Tags (provided at the dispatch ends of station) are
read by Loco ACD with the help of by ‘RF Tag Reader’,
fitted in the under frame of Locomotive
Track-ID (TID) Assignment – While Leaving a Station – MULTIPLE LINES SECTION
T1
RF Tags
TID = 15
TID = 16
TID = 14
TID = 17
RF Tags

Initialization of ACD fitted Train
• At Train originating Station, Guard ACD is loaded and switched ‘on’.
• As soon as Train starts, Loco ACD will identify ‘automatically’ its Guard
ACD and radiate its ‘Guard ACD – ID’.
• On receipt of data packet from a Loco ACD containing its ‘ACD-ID’, the
Guard ACD will assume the ‘Loco ACD-ID’ and ‘Track-ID’ of that Loco
ACD, thus forming a ‘CYBER’ Train.
• Loco ACD will conduct an ‘Auto Brake Test’ (ABT), moment its speed
becomes 50 Km/hr and reduce it by 20 Km/hr to deduce the ‘braking
characteristics’ of its Train
• ACD fitted train would now apply brakes based on its braking capacity,
whenever a collision-like situation is perceived.

Prevention of Collision in ‘Mid-section’ - 1
Prevention of ‘Head- on’ Collision
TID =11
TID =12
T1
T2
Prevention of ‘Rear- end’ Collision
TID =11
TID =12
T1 T2

Prevention of Collision in ‘Mid-section’ - 2
Prevention of ‘Side’ Collision
TID =11
TID =12
Stationary (might have derailed)
T1
T2
Prevention of ‘Side’ Collision
TID =11
TID =12
Train Parted, Derailed & Infringing Adjacent Track
T1
T2

Prevention of Collision at Level Crossing
Manned Level Crossing (Open)
TID =11
TID =12
‘Hooter’ / ‘Flasher’ to give
‘Train Approach’ Warning to Road Users
T1
Lifting Barrier Gate
TID =11
TID =12
T1
Road
‘Hooter’ / ‘Flasher’ to give
‘Train Approach’ Warning to Road Users
Un-Manned Level Crossing

Prevention of Collision in Station Area -1
Prevention of ‘Head-on’ or ‘Rear-end’ Collision
TID =11
TID =12
TID =10
T1 T2
‘Station Approach’ Warning to Driver
TID =11
TID =12
T1
Station

Prevention of Collision in Station Area - 2
Prevention of High speed Collision with
Train on Loop Line (RNSML)
TID =11
TID =12
TID =10
T1
T2
TID =12
Prevention of Collision with ‘Stabled’ Load
on Main Line
TID =11
TID =10
T1 SL

Prevention of Collision in Station Area - 3
Prevention of Collision due to ‘Fouling’ (Multiple Lines)
TID =11
TID =12
TID =10
TID =13
T1
T2
Prevention of Collision due to ‘Fouling’
TID =11
TID =12
TID =10
T1
T2

‘128’ Train Collisions in FIVE Years on Indian Railways
Analyzed by Rly Board (with RDSO & KRCL) –
(April 1997 to January 2002)
23 (18%)
13
10
Total
08
07
01
Side Collision
3
03
01
02
Rear-end Collision
2
12
05
07
Head-on Collision
1
Total
Station
Mid-Sec.
‘Non-Preventable’ by ACD
Sr
105 (82%)
60
45
Total
22
16
06
Side Collision
3
44
11
33
Rear-end Collision
2
39
33
06
Head-on Collision
1
Total
Station
Mid-Sec.
‘Preventable’ by ACD
Sr

Train Collision Scenarios: ‘Non-Preventable’ by ACD
• ‘Adequate’ braking distance at that speed is not available when a
‘dangerous’ collision-like situation arises suddenly
• Train derails and its wagons/coaches dash with another Train,
already on ‘adjacent’ track
• Overshooting of ‘Fouling Mark’ by a Train on main line
• ‘Failure’ of brake power of Locomotive due to any reason
• Rolling backward/forward of a ‘Stabled load’
• Other train is a ‘NON’ ACD Train

ACD Project
‘Corporate Safety Plan’ (2003 - 2013), Indian Railways
2013-14
Balance ‘ACD Works’ covering
52,600 Route Kms over
Indian Railways
2
2007-08
‘ACD Works’ already sanctioned
on
3,419 Route Kms over
Indian Railways
1
Target for
Completion
Description
Sr

Total Provision of ACDs
Northeast Frontier Rly & Konkan Rly
ACD Project on Req. Spare Tot
NF Railway 1,382 126 1,508
Konkan Railway 720 98 818
Total 2,132 224 2,326
Loco ACDs - Loco shed wise Req. Spare Tot
NF Railway ( 13 Loco Sheds ) 589 27 616
Konkan Railway ( 06 Loco Sheds ) 111 14 125
Total ( 19 Loco Sheds) 700 41 741

‘ACD Project’ - Works Already Sanctioned over IR
4
Southern Rly (including part of South Western Rly) –
Ernakulam – Shoranur – Palghat – Erode – Chennai
and Bangalore – Jolarpettai – Chennai
3
2
Northeast Frontier Rly –
Pilot Project Commissioned (June 2007)
1
Provision of ‘Anti-Collision Devices’ (ACDs) on Broad Gauge (BG)
Routes of Indian Railways
Sr
South Central Rly (including part of South Western Rly) –
Vasco – Madgaon – Londa – Hubli – Guntakal – Renigunta
Northern Rly –
Jalandhar – Amritsar

7
1
4
8
1
2
1
3
5
5
1
6
6
9
4
1
5
3
2
1
1
0
1
1

“I need the ACD, ACD does not need me” – Train Driver
‘Anti-Collision Device (ACD) Network’ – © Konkan Railway Corporation Limited, India

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