Malfunction on new branch of Montreal rail network caused by signalling system

The Réseau express métropolitain (REM) train has a test run from downtown Montreal, Wednesday, July 19, 2023. (THE CANADIAN PRESS/Christinne Muschi)

A problem with the signalling system caused a service interruption for several hours Friday morning on Montreal’s light-rail network.

The malfunction occurred on the new branch of the rail system that opened last month, connecting downtown Montreal with its northern exurb of Deux-Montagnes, Que.

A spokesperson for Pulsar, which operates the REM — Réseau express métropolitain — said the signalling system allows the automated trains to recognize the tracks ahead and the presence of other trains or objects.

The problem was detected as service was being launched Friday morning on a section of the track that includes six stations on the Island of Montreal, said Maxime Laliberté in an email.

The network first announced the service interruption around 5:30 a.m. on social media. Service was suspended at several stations until the problem was resolved around 9:30 a.m.

Laliberté did not say whether the issue was linked to the frigid weather in Montreal, with temperatures feeling like -23 C with the wind chill on Friday morning.

The first leg of the light-rail network, which connected Montreal’s South Shore to the city’s central station, was plagued by frequent service interruptions after it opened in 2023.

Last winter, the REM had problems with de-icing switches, which allow trains to be directed from one track to another. But Friday’s malfunction involving the signalling system was unrelated, Laliberté said.

The new 30-kilometre extension of the REM travels northwest from central station, through a tunnel under Mount Royal linking the campuses of McGill University and Université de Montréal, before it continues along the north end of the island and on to Laval, Que., and the Deux-Montagnes station.

Two other branches are yet to be opened. One branch to Montreal’s West Island suburbs is expected by spring 2026, while a branch to Montréal Trudeau International Airport is expected at some point in 2027. Once complete, the network will have 26 stations across 67 km.

By Maura Forrest

This report by The Canadian Press was first published Dec. 5, 2025.