Work on the REM light rail line has already begun, but a group of environmental advocates are hoping it’s not too late to stop it.

In an open letter sent Saturday, the group called for work on the REM to stop, saying it would do little to alleviate Montreal’s traffic and would cause only a negligible reduction in greenhouse gas emissions.

Lisa Mintz, co-founder of Trainsparence, signed onto the letter. She said the REM is focused on the West Island and South Shore, ignoring congestion in the eastern portion of Montreal.

While the City of Montreal has announced a five-stop extension of the metro’s blue line eastward and the purchase of 300 new buses, Mintz said existing public transportation systems will be in competition with the new REM.

“It’s not a complimentary system, it’s actually sort of a takeover,” she said. “Most of the REM stations in the west island are at least a kilometer away from where people live. This to me has always been a real estate project.”

Also signing onto the letter are members of environmental groups like Coalition Verte and residents of Laval, Oka and Montreal.

The group advocated for the Parti Quebecois’ recently unveiled transit plan, nicknamed the “Grand Deblockage,” or Big Breakthrough. That plan called for an expansion of Montreal’s bus network with several express routes, improving the existing commuter rail system and building five tram lines that would serve different areas of the city.

The REM system will cost the city and province an estimated $8 billion over the first 20 years. Construction officially began with a groundbreaking ceremony last week and trains are expected to begin running in 2024.

Last week, it was announced construction on the project will cause some service interruptions on the  Deux-Montagnes and Mascouche train lines and will result in the closure of the Mount-Royal Tunnel beginning on April 27 and lasting until Fall, 2019.