Construction of Montreal’s upcoming light-rail system will officially begin with a symbolic groundbreaking on Thursday afternoon, but the work will cause headaches for the city’s already beleaguered commuter train users.

The multi-billion REM system will connect the West Island and South Shore to Montreal and the kickoff will be attended by federal Transport Minister Marc Garneau, Quebec Premier Philippe Couillard, Montreal Mayor Valerie Plante and the heads of the Caisse de Depot and SNC Lavalin.

Months after snow caused numerous delays, leading to an offer of 30 per cent discounts on monthly train passes, the Reseau de Transport de Montreal announced that the construction of the REM will affect two of its train lines. While the REM will use some of the RTM’s existing tracks, the two types of train use different electrical voltages, necessitating some work.

As of April 27, trains traveling between Mascouche and downtown Montreal will be cancelled on Friday nights.

The Deux-Montagnes line will also see some cancellations, and both lines will be closed entirely on weekends. The RTM said they expect to announce alternative transport options soon.

The work on the two lines is expected to last until next fall at the soonest.

According to the RTM, 4,600 trips are made on the Deux-Montagnes line during weekends alone, accounting for three per cent of all trips made on RTM tracks.