The extension of the metro to Laval required the addition of a runaround track past the existing Henri-Bourassa terminus station, and the addition of a third platform on this runaround track. This addition was required in order to meet scheduling needs. Since the traffic coming from Laval is projected to be lower than that within Montreal, only one of every two trains will go to Laval; the other will end its run at Henri-Bourassa. Accordingly, a third platform is needed to avoid conflict between trains terminating at Henri-Bourassa (which will use the existing platform before waiting in the tail track) and trains continuing to Laval (which will use the new platform). Adding a new section to an existing metro station is of course a major undertaking, and service had to be first restricted, then halted, at Henri-Bourassa station in order to allow work to be carried out. This took place throughout spring and summer 2004. First, in order to allow work in the tail tracks, the usual departure platform (the Côte-Vertu platform) was closed for four weekends during April and May 2004. This was because the trains could not enter the tail tracks to carry out their usual switching manoeuvre during the work, so they had to use the usual arrival platform both for loading and unloading, and then change lines across the switch in the fore-tracks.

For a brief period just before the station's closure in May, signals testing required the line north of Berri-UQAM station to be closed for two weekend nights and a Saturday morning. Trains ended at Berri, and a provisional bus service was set up serving the stations between Berri and Henri-Bourassa. Finally, on 15 May, Henri-Bourassa station was closed. Owing to the location of the switches between Crémazie and Sauvé stations, it was necessary to send only one out of every two trains to Sauvé during rush hour, although outside of rush hour all trains ended at Sauvé. Destination was announced by panels at the front of the trains, and also by vocal announcements as the train neared the terminus. There were frequent scenes of crowding on Crémazie's Henri-Bourassa platform as people waited for the next train, which would continue to Sauvé.

Bus routes were substantially modified, with reserved lanes being set up to accomodate the increased traffic. STM buses were rerouted to Sauvé, Crémazie, and Jarry stations; some STL buses were rerouted to Sauvé or Côte-Vertu. Also, a provisional shuttle bus service — the 545 Henri-Bourassa–Crémazie — provided free, non-stop service every 1-2 minutes between Crémazie and Henri-Bourassa, loading in the bus loop behind the Crémazie Nord access and unloading in the Henri-Bourassa Sud bus loop. Not only did this serve regular users of Henri-Bourassa station, but also maintained access to a number of bus lines that were not redirected. (The tunnel between Henri-Bourassa Nord, Henri-Bourassa Sud, and Terminus Laval entrances was kept open to allow pedestrians to cross Boul. Henri-Bourassa safely.) The shuttle bus went to Crémazie instead of Sauvé because of fears of overcrowding at Sauvé and the availability of a bus loop at Crémazie. Note that Sauvé was only using one platform owing to the location of the switch, much as Henri-Bourassa had done in April and May; crowds were fierce and exacerbated by the station's narrow corridors. During the closure, the runaround tunnel and trainroom were excavated, the switch was installed where the runaround track and main track meet south of the station, and the accesses were pierced between the new trainroom and the existing station. In this panoramic view of the site, the north end of the track (toward Laval) is at left, the south end (toward the existing tunnel) is at right. There will be a total of three accesses to the new platform. The first will lead to the corridor between the existing trainroom and the eastern mezzanine. The construction also included room for an elevator, though the STM will have to undertake to install the elevator itself and prepare elevator access to the surface and to the other two platforms. As the new excavation passes directly underneath this corridor, it was a tricky operation to dig under it while ensuring that it would remain stable. Another access is from the south stairwell between the existing arrival platform and the bridge over the tracks.

Finally, a tunnel will connect the southern parts of the two platforms directly. The closure went exactly as planned; bus service met expectations, passengers were only mildly inconvenienced, and the station reopened right on schedule on 23 August, with bus service returning to normal. However, there is still plenty of work to do at this station: the tunnel must have its concrete walls constructed, the track bed must be built and the tracks laid, the platforms must be constructed, the architecture finished, and technical installations put in.

Links:
(all of the below are in .pdf format and in French)