An investigation into a signal failure that allowed an Electric Multiple Unit (EMU) to enter a line occupied by two other trains in Southern Railway’s Chennai Division has exposed serious lapses in compliance with safety protocols.
Documents accessed by The Hindu revealed that the automatic signal, S192, in the Ambattur-Avadi section malfunctioned over 50 times in February 2026 alone. A buzzer installed in the Ambattur Station Master’s office to alert the staff to signal failures was found to have been “disconnected”. The defective signal was repeatedly reset by field technical workers without analysing the root cause of the malfunction. This allowed the problem to recur over several months.
The incident occurred on March 5 this year in the busy suburban section. The signal displayed a ‘Double Yellow’ aspect, authorising the EMU to proceed on a line occupied by two other trains. But the alert motorman noticed the trains ahead and applied the brakes, bringing the EMU to a halt just before the occupied section and averting a disaster. He photographed the situation and reported it to his superiors. A multi-departmental inquiry by senior officers found that the repeated failures of the signal had not been subjected to any root-cause analysis.
During the failure of the Multi-Section Digital Axle Counter (MSDAC), a critical train detection and signalling system, field staff members merely replaced defective sensors without investigating the underlying cause of the malfunction. As a result, spare sensors were consumed at an unusually high rate while the defect remained unresolved.
Records showed that dozens of signal sensor failures were reported in the section in February 2026. The signal S192 alone failed on 53 occasions, significantly more than those in other sections. Although alerts about the failures were circulated through WhatsApp groups, officials did not identify the root cause or initiate corrective measures, the inquiry found.
The inquiry concluded that the incident resulted from a series of systemic failures. The Ambattur Station Master remained unaware of the malfunction because the warning buzzer in his office was not functioning. The signal maintenance staff adopted a shortcut method to reset the faulty sensor instead of carrying out a diagnosis. The signalling system’s diagnostic panel was also found to lack fail-safe safeguards.
“There was a failure of SMS alerts from the data logger to notify the Senior Section Engineer of a potential reset attempt in the MSDAC hut,” the inquiry report said. According to the report, these lapses collectively led to the malfunction of S192, which permitted the EMU to enter a line occupied by two other trains.
Published - July 14, 2026 09:03 pm IST