Montreal's Réseau express métropolitain (REM) light rail system experienced a major service disruption on the morning of Friday, December 5, 2025, affecting a significant portion of the network during the crucial morning commute. Service was fully restored by approximately 11 a.m. after hours of outages.
Timeline of the Friday Morning Disruption
The first alerts regarding service problems were issued by the REM via its official X account and text message alerts at 5:34 a.m.. Initially, service was halted between the Du Ruisseau station in St-Laurent and the Édouard-Montpetit station in Outremont.
The situation escalated rapidly. Within minutes, the outage extended to cover the segment from Bois-Franc to McGill station. By 6:26 a.m., the disruption had reached Central Station, severely limiting connectivity across the network.
A gradual restoration process began later in the morning. Partial service returned to the Côte-de-Liesse station just before 9 a.m. The network then progressively came back online between 9:30 a.m. and 10:11 a.m., according to official alerts, with full system recovery achieved around 11 a.m.
Cause and Operator Response
Maxime Laliberté, speaking for Pulsar, the system's operator, identified the core issue as signalling problems between the Du Ruisseau and Édouard-Montpetit stations. The decision was made to close additional stations as a precautionary measure. This strategic shutdown allowed Pulsar to maintain limited service on the Brossard to Central Station segment, preserving a vital link for South Shore commuters.
"Teams were immediately dispatched to address the problem, and service has been restored," Laliberté stated. He confirmed that Pulsar teams will conduct a thorough investigation to determine the root cause of the signalling failure. Throughout the interruption, shuttle bus service was implemented to mitigate the impact on stranded passengers.
A Pattern of Recent Service Interruptions
This incident marks the second major outage since the inauguration of the REM's Deux-Montagnes branch on November 20, 2025. The network experienced a significant disruption on November 21, when service was halted for about two hours after a truck struck an overpass near the Bois-Franc station.
Earlier this week, service was also interrupted for approximately thirty minutes due to an intrusion on the tracks. As a fully automated system, the REM is designed to halt all trains immediately when a trespasser is detected on the guideway, a safety feature that inevitably causes system-wide delays.
The system's vulnerability to external events was tragically highlighted just days prior. On November 22, two brothers, 19-year-old Simon Brochu and 22-year-old Samuel Brochu, died after being struck by a REM train around 3 a.m. while attempting to cross the tracks at Highway 10. That incident also caused several hours of service disruption on the South Shore branch.
Friday's widespread outage underscores the growing pains of Montreal's newest and highly automated public transit system as it integrates into the city's transportation fabric. Commuters and officials alike will be awaiting Pulsar's findings on the cause of the signalling failure.
