Skip to main content
A new commissioning sequence for the REM - Crédit photo : Alstom/C.Fleury

A new testing and trial sequence to optimize the REM’s commissioning schedule

Project progress
Published on

Update - December 2022

The REM commissioning schedule has been updated. To view the latest version, visit our Work Schedule page.

The major challenges posed by the Mount Royal Tunnel have forced our teams to rethink the testing and trial sequence for the REM’s commissioning, in order to support efforts to commission the network by late 2024 and avoid significant delays.


A revised and optimized commissioning schedule

The REM was initially supposed to open in 5 phases: the South Shore portion in fall 2022; the central segment in fall 2023; the West Island segments in spring 2024; the North Shore segment in fall 2024; and lastly the airport portion in late 2024.

Today, our teams have simplified the commissioning schedule into 3 phases:  

  1. South Shore branch (Brossard-Central station, excluding Griffintown-Bernard-Landry station*): maintained for fall 2022.
  2. Downtown, North Shore and West Island branches: simultaneously for late 2024.
  3. YUL-Aéroport-Montréal-Trudeau branch: We are working with Aéroports de Montréal to align and optimize the new schedule, and to be able to confirm that this REM branch will be commissioned this fall.

GIF of the old schedule (updated in November 2020) and the new REM commissioning schedule. The previous commissioning schedule (updated in November 2020) for the REM has been revised.

Enlarge image


A change to avoid postponing commissioning to 2026

Making this change is necessary due to the exceptional and unforeseen circumstances surrounding the modernization of a 5.2-km stretch of the Mount Royal Tunnel, which continue to affect operations:

  • The discovery of explosives left behind from the tunnel’s construction over 100 years ago, which has disrupted all of the work methods used. 
  • The generally degraded conditions of the central wall of the tunnel’s arch where it runs beneath McGill College Avenue. 
  • The impacts of COVID-19 over the last two-plus years (labour and supply chain).

In the face of these colossal challenges, it is not possible to begin the required tests in the tunnel before summer 2024. These tests are critical to a safe commissioning. 

The situation in the tunnel would have resulted in the whole commissioning sequence of the Deux-Montagnes and Anse-à-l’Orme branches being delayed until 2026. The past few months have been spent establishing a solution to optimize the test schedule and to maintain a commissioning target of late 2024. 

See the new schedule for more information.

More info on the revised schedule

GIF of the McGill worksite Our field teams deserve recognition for their hard work. They completed the drilling for most of the holes using a highly safe but more complex and time-consuming method.
Jean-Philippe Pelletier, Eng., Director, Deux-Montagnes Sector

“The modernization of the century-old Mount Royal Tunnel is a huge challenge for every team. Despite the many challenges, everyone fully mobilized to advance the work as quickly as possible. Approximately 90% of the drilling and excavation work has been completed. The reconstruction and repair work on the double arch is well underway and will be finished this summer, and the central wall is also progressing rapidly—all while ensuring everyone’s safety at every step.”

Jean-Philippe Pelletier, Eng., Director, Deux-Montagnes Sector

Importance of testing phases

Before a transit system can be commissioned, it must be fully tested. The network’s opening is dependent on whether these tests succeed.

The South Shore maintenance centre will not be able to perform its scheduled tests since the Mount Royal Tunnel will still be under construction, so the teams had to think of another solution for deploying its next test phases. For more information about the tests, visit our news section. 

Learn more about the tests

“The unforeseen events in the tunnel have forced us to be very agile and develop a solution for redeploying the tests and the commissioning sequence. Lastly, with the redeployment of the ‘North-South Plan’ sequence, the project schedule has been optimized and the North and West segments will stay on track for their commissioning in 2024, with the tunnel issue considered. I’m proud of the innovation and ingenuity shown by our teams in developing this plan.” 

Denis Rivard, Vice President, REM Project  

Denis Rivard, Vice President, REM Project

The solution: a “North-South Plan” that completely rethinks how the tests are deployed

Over the past few months, our team developed a plan, dubbed the “North-South Plan,” in a concerted effort to innovate and prevent the REM’s commissioning from being delayed by several months. Our priority was to commission the entire network safely, as quickly as possible, especially for users of the former exo Deux-Montagnes and Mascouche train lines. Here are the approach’s key components:

Reverse the dynamic testing sequence to stay on track for the 2024 opening of the North and West segments.

Deploy tests and trials from the Saint-Eustache maintenance centre instead of the one in Brossard.

Isolate the Mount Royal Tunnel from testing to ensure that once the work and testing is done, the entire network will be ready and commissioned by late 2024. 

The cars and systems tested for the pre-commissioning test phases will be launched from the Saint-Eustache maintenance centre; in other words, the starting point for the testing has been reversed. Instead of starting from the South Shore and gradually working northwards, the tests will begin from the North Shore, avoiding the Mount Royal Tunnel issue and preventing delays to vital testing on the rest of the network. 

GIF of challenges

Enlarge image


In summary, the tests will take place in the following order: 

  1. Phase 1: Saint-Eustache maintenance centre to Sainte-Dorothée station
  2. Phase 2: Sainte-Dorothée station to Côte-de-Liesse
  3. Phase 3: Anse-à-L'Orme (west) branch
  4. Phase 4: Côte-de-Liesse to Central station (finally, including the Mount Royal tunnel)
Image of the Saint-Eustache car maintenance centre Did you know that there is also a car maintenance centre in Saint-Eustache? This centre holds 84 cars in total and will be the largest REM maintenance centre and train depot.

Coordinating to maintain transitional measures

Discussions are underway with our partners, the ARTM and Mobility Montréal, to maintain the transitional measures put in place to address the complete closure of the exo Deux-Montagnes line and the disruptions to the exo Mascouche line.  

For more information, visit the Mobility Montréal website.