Train Protection and Warning System (TPWS) on trains

ALLAHABAD: To prevent train accidents, North Central Railway has installed Train Protection and Warning System (TPWS) on trains. This protection device would automatically apply brakes on a train if it crosses a signal or is over speeding. The system has already been installed on three trains and is functioning effectively. The trains on which it has been installed are 2279/2280 Taj Express, 2911/2912 Valsad-Haridwar express and 4211/4212 Agra- New Delhi intercity express.

TPWS automatically applies a trains brakes if it approaches a fitted signal at danger too fast or fails to stop at a signal set at danger. It also automatically applies the brakes if a train is travelling too fast on the approach to certain speed restrictions and buffer stops.

A standard TPWS installation consists of an on-track transmitter placed adjacent to a signal and activated when the signal is at `danger’ point. Any train that tries to pass the signal will have its emergency brakes activated. If the train is travelling at speed, this may be too late to stop it before the point of collision, therefore a second transmitter may be placed on the approach to the signal that applies the brakes on trains going too fast to stop at a signal, and this is positioned to safely stop trains approaching at upto 75 mph (120 km/h).

One pair of electronic loops is placed 50-450 metres on the approach side of the stop signal. The distance separating the loops is used to control the speed of the train.

There is another pair of loops at the signal, also energised when the signal is at “danger”. These are always placed immediately together and will stop a train that runs past the signal, regardless of its speed.

In a standard installation of TPWS, there are two pairs of loops (sometimes referred to as “grids” or “toast racks”). Both pairs consist of an `arming’ and a ‘trigger’ loop. If the signal associated with the TPWS is at “danger”, the loops will be energised. If the signal is at “proceed”, the loops will de-energise.

The first pair, the Overspeed Sensor System, is fitted at a position determined by line speed and gradient. The loops are separated by a distance that should not be traversed within a pre-determined period of time (about 1 second) if the train is running at a safe speed approaching the signal at “danger”. The other pair of loops is back to back at the signal, and is called a Train Stop System ( TSS).

NCR chief public relations officer RD Bajpai told TOI that TPWS is a foolproof system that would prevent train accidents and thus ensure safety of passengers. The system would be installed on more trains soon, he said.

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