1. ANTI COLLISION SYSTEM
FOR TRAINS

2. WHAT IS AN ANTI COLLISION SYSTEM ?
The anti collision systems for trains is an electronic device designed to ensure the safety and proper operation of the trains in order to avoid the risk of dangerous and unexpected collisions of the trains which may be caused due to human errors and equipment failures.

3. TYPES OF ACD’S IR Based System
There is an IR transmitter and an IR sensor fitted on the Train’s Locomotive.
System works in Line Of Sight(LOS).
The sensor is connected to the Braking circuit which is connected to a stepper motor which applies brakes to the train.

4. DRAWBACKS
IR system only works in the Line Of Sight (LOS) i.e the system fails on curved tracks.
It cannot prevent REAR-END collisions, SIDE-TRACK collisions.
The range of the system depends on the IR transmitter power. The more power , the lesser is the reaction time.
This system is drastically affected by whether conditions as rains and other conditions interfere with the IR signal.

5. GPS Based ACD
Conceptualized by B. Rajaram director of konkan railways.
Self-acting microprocessor based electronic device.
Takes inputs from the G.P.S satellites and network with other A.C.D’s to detect any collision like situation.
Range of 3 km.
Prevent head-on collisions, side track collisions, rear-end collisions.
Can be installed on the locomotives, guard vans ,at stations and at level crossings .

6. A.C.D units comprising the whole A.C.D network
The Loco ACD (Fixed & Moving) is permanently installed in the locomotive along with its ABU( Automatic Braking Unit) .
The Guard ACD (Portable & Moving) is portable A.C.D and acts as a backup for the locomotive A.C.D in case the locomotive A.C.D stops transmitting the signal .
The Station ACD is permanently installed in the stationmaster’s office. He can send manual SOS through his station ACD by pressing SOS buttons when he notices anything unusual like a hot axle or fire in a train while performing train passing duties.
The Level Crossing Gate ACD is permanently installed in a Gate Man’s cubicle and informs other A.C.D’s about any emergency at the LC.

7. Fig 2.3 Unit for Locomotive
A glance at the G.P.S based ACD unit
Fig 2.3 Unit for Locomotive
COMPONENTS of ACD
G.P.S (Global Positioning System)- Get the position updates
C.C.U (Command and Control Unit)- Decision making device
Radio Trans-reciever- For inter-ACD communications
(A.B.U) Automatic Braking Unit

8. Working of an A.C.D functional unit G.P.S C.C.U (BRAIN)
CONSTELLATION of SATELLITES
G.P.S
Picks up signal from the satellites
(exclusive network of Satellites)
Submits data to C.C.U
for further processing
C.C.U (BRAIN)
Extract parameters
LATTITUDE
LONGITUDE
SPEED
ANGLE
DATE & TIME
RADIO TRANS-RECIEVER
Transmits the Train ID , Speed, Location
Receives info sent by other
A.C.D’s (within 3 km range)
A.C.D’S exchange info and the C.C.U takes a decision based on a working rule
AUTOMATIC BRAKING UNIT
Gets input from C.C.U
Apply normal brakes/ emergency brakes
TRAINS COME TO A HALT IF ON A COLLISION PATH (AUTOMATICALLY)
Deduce if the trains are on a collision path

10. Situations where A.C.D can prevent a collision1. 2.

11. 3.

12. Situations where A.C.D can’t prevent a collision (Worst Case Scenario)
In the following cases the A.C.D network fails
Other train is a ‘NON’ ACD Train – ACD functions by reacting to another ACD, as such if one of the two trains is a non-ACD train, the protection against collision will be missing.
‘Adequate’ braking distance at that speed is not available when a ‘dangerous’ collision-like situation arises suddenly – However, severity of the collision would be reduced as a function of the reaction time.
‘Failure’ of brake power of the Locomotive/train – This situation arises when there is any electrical failure and the brakes become non functional.

13. BENEFITS OF THE ACD SYSTEM
Acts automatically to prevent collisions if an eventuality arises. Does not depend on human action.
Designed and engineered to make the system very rugged, and able to withstand harsh environments
The Loco ACD operates directly from the engine battery; the LC gate ACD can be powered by solar power systems, if required.
Very economical and cost effective.
Does not degrade the existing safety level.
No cabling on the track required (which is more expensive and cumbersome)‏.
It does not require any inputs to be fed by the crew at the start of journey, thus human error is eliminated.