Commuters using train service in the Montreal area can’t expect their transit to be on time right now, officials with Exo, the regional train service, say.

In a news release Tuesday evening, Exo said that work on the REM light-rail system means they can’t guarantee punctuality on the Deux-Montagnes and Mascouche lines.

They say the Mont-Saint-Hilaire, Vaudreuil-Hudson and Saint-Jérôme will not be affected.

Since June 25, the Deux-Montagnes and Mascouche lines have been operating on a single track between the Montpellier station and the entrance to the Mont-Royal Tunnel as work begins for the anticipated light-rail service.

Exo (the new name for the former RMT) said the single-track system is causing “major operational constraints.”

Due to these constraints, Exo said it “no longer has the necessary leeway to ensure the punctuality of its trains on the affected lines.”

Now, said Exo, in the event of any event affecting a train – be it a mechanical problem or a medical intervention on board, for example – all trains that cross or follow it are likely to be delayed, creating a bottleneck.

Exo said it “understands and shares the frustration of its customers” and is doing everything in its power to limit the impact of service during REM work.

In April, train authorities announced the suspension of weekend service on Deux Montagnes and Mascouche train lines during REM construction.