Outdated signal system caused Secunderabad-Shalimar train accident in 2024, says railway probe

The Secunderabad-Shalimar Weekly Superfast Express derailed at West Bengal’s Nalpur station in November 2024 due to a poorly maintained signal equipment that was over three decades old and had outlived its life even at the time of commissioning in 1999, a railway probe has said.

Soon after the incident, railway officials had called it an unprecedented, stating that when the train’s engine was moving on the main line and had just crossed a track changing point (Point no 26), a sudden command to the interlocking system diverted the coaches onto another line, leading to the derailment of three coaches. The incident didn’t cause any casualty or injuries to passengers.

The probe found that the command was sent to the signalling system by mistake because a signal maintainer’s body part hit the signal equipment (latch relay of rack #1) unintentionally while repairing the fault of some other line signal (relay rack #2) in the relay room.

“During enquiry, the night signal maintainer confessed that during his attempt to fix the failure of S-10, he stooped down to see the condition of 10 NNR Relay (Q series) on relay rack #2 and while standing up, he casually rubbed the K-50 Siemens latch relay for point no 26 installed on relay rack #1,” Manish Kumar, Deputy Chief Safety Officer (Signal & Telecom), East Central Railway zone, said in a safety bulletin, circulated to senior officials on August 23, 2025.

According to Kumar, the relay rack #2 and relay rack #1 face each other at merely 84.5 cm distance.

“Thus It was concluded that the derailment of Train no 22850 at Nalpur on 09.11.2024 has taken place due to under-wheel operation of point no 26 B while the train was passing over the said point. The underwheel operation of point no 26 B has taken place due to unintentional shaking of the K-50 type Siemens relay by the night signal maintainer while he was attending the failure of Down Common Loop Starter Signal S-10 in the relay room,” Kumar added.

Analysing the fault in the signalling system, Kumar stated that the probe found that K-50 relay used for point no 26B was manufactured in September 1989 and was commissioned at Nalpur in March, 1999.

“So, this relay has already outlived a considerable period of its life (around 10 years) at the time of the commissioning of the system. So, it should be ensured that equipment being installed should not be much older (not more than two years) at the time of commissioning,” Kumar suggested.

Besides the outdated signalling system, the probe also highlighted its poor maintenance as well.

“On inspection of the relay room at Nalpur, it was discovered that out of two screws provided for holding such relay on the relay rack, only one top screw was tightened up and no bottom screw was provided which was required to fix it firmly and hold the relay tightly,” Kumar said.

He stated that in order to study the behaviour of such type of Siemens K-50 relay, the Inquiry Committee tried to simulate the situation at the same type of installation and similar kind of work at Satragachi PI (panel interlocking) installation.

“The same type of relay was located in the relay room of Satragachi (in Kharagpur rail Division) in similar fashion, with bottom screw not located and top screw was kept in loose connection. The relay was put in normal latch position and similar kind of rubbing by the human back was simulated,” Kumar said.

He added, “It was found that in most of the cases, when such jerk was given to the said relay, detaching took place within the relay. It was repeated several times and similar results followed. This simulation was repeated with other similar healthy K-50 relay and result was the same.” The probe also revealed that the essential principle of signalling was violated in the said incident.

“In a sound design of the circuit, failure of one signal component should not result in a major unsafe incident. A second layer of design, and hence its interlocking, providing a fail-safe route of the moving train over a critical component should have been there,” the probe said.

The probe recommended the replacement of such old systems with the new ones at all other stations where this system is still in use.