DT Next Exclusive | Data logger at Kavarapettai station reveals ‘failure’ within 7 min

CHENNAI: The data logger at Kavarapettai station has revealed the puzzling moments leading to the collision between Train 12578 (Mysuru-Darbangha Bagmati express) and the stationary goods trains on the loop line on Friday night.

A video of the data logger recording at Kavarapettai station accessed by DT Next from highly-placed Southern Railway (SR) sources showed that another train passed the green signal (NWKR) and proceeded on the main line (51T-01/01AT) in the same direction on the same spot exactly seven minutes before.

A thorough analysis of the 41-second video-recording of the signal relay from 8.20 pm to 8.50 pm at Kavarapettai station revealed that the signal turned green (NWKR) for 51T-01/01AT (mainline) at 8.22 pm for another train. The first train crossed the spot on the main line at 8.23 pm.

At 8.28 pm, a green signal after two yellows and a red, was given for Bagmati express from Ponneri to continue on the main line. As per the data logger, the train entered the phasing point at 8.30 pm. Exactly 10 seconds later, the data logger showed both 51T (main line) and 51 (loop line) remaining red, suggesting that the train was on both the routes at 8.30 pm.

Railway officials familiar with the signal functions told this paper, “If the first train passed the green signal on the main line without any problem, why did the Bagmati xxpress veer into the loop line 7 minutes later for the same signal? Though it’s too early to rule out sabotage, there is no way someone could manually interfere and tamper the point system between the crossing of the first train and sanction of the green signal for Bagmati express in four minutes.”

There could only be a few possible explanations. One would be the likely gap, or the lack of it, between the stock rail and tongue rail at the Phasing Point (point from where a train could go straight to steer to another side) or the wearing out of the tongue rail. If the gap between the stock and tongue rail is wide, the train will proceed straight on the mainline as usual.

If the points are not aligned correctly or if the gap is too narrow, the wheel flange could be steered into the loop line by rail flange or the tongue rail. Also, if the edge of the tongue rail is worn out, the wheel flange could have climbed and steered the train into the loop line.

Another possible reason could be the failure of the sensors at the splitting of points or phasing Point. The signal might have been issued for green mainline, but the sensor failure might have shown green on the panel of the station master and the signal pole, but the points might have been actually aligned for the loop line, which would be difficult for the loco pilot to observe from distance at such velocity though he is expected to do so. A malfunction or wear-and-tear in the sensors might have contributed to such contrary indication (right signal but wrong joint relaying).

Ruling out the possibility of a worn-out locomotive wheel, which could also contribute to such incidents in rare cases, a railway officer said that such wear and tear could be accepted in the wheels of the coaches even, but “the chances of worn out locomotive wheels leading to wrong turn is remote or close to improbable”.

Officials opined that the authorities must also examine when the Permanent Way inspector and Signal Inspector conducted the mandatory joint inspection of the points.

Another possible reason could be the failure of the sensors at the splitting of points or phasing Point. The signal might have been issued for green mainline, but the sensor failure might have shown green on the panel of the station master and the signal pole, but the points might have been actually aligned for the loop line, which would be difficult for the loco pilot to observe from distance at such velocity though he is expected to do so. A malfunction or wear-and-tear in the sensors might have contributed to such contrary indication (right signal but wrong joint relaying).

Ruling out the possibility of a worn-out locomotive wheel, which could also contribute to such incidents in rare cases, a railway officer said that such wear and tear could be accepted in the wheels of the coaches even, but “the chances of worn out locomotive wheels leading to wrong turn is remote or close to improbable”.

Officials opined that the authorities must also examine when the Permanent Way inspector and Signal Inspector conducted the mandatory joint inspection of the points.

What’s a data logger?

A data logger is a mechanism of recording the actual position of signals and points as received by the equipment from the signal system. A data logger at a station records the relay of signals and points within the geographic or operational limit of the station in a real-time basis

Normal Point Indication Relay (NWKR): A green signal given after two yellows and a red to allow trains to continue on the main line

Reverse Point Indication Relay (RWKR): A signal issued specifically for trains to enter the loop line

Stock rail: The straight rail guiding the train to continue on the mainline

Tongue rail: The curved rail lined along the stock rail to guide the train into the loop line