Noise from the Réseau express métropolitain (REM) will be significantly reduced by spring in Griffintown, Pointe-Saint-Charles and L’Île-des-Sœurs. The Caisse de dépôt claims to have respected its promises, but the noise environment around the light rail will nevertheless remain quite high.
The story so far
May 2023
To calm the discontent caused by the noise of passing REM trains, the Caisse de dépôt is launching sound tests.
July 2023
The CEO of CDPQ Infra, Jean-Marc Arbaud, announces the arrival of fixes.
September 2023
Grinding and insertion work for dynamic absorbers begins. The first project ends in January, the other is postponed until spring.
February 2024
A reduction of 8 decibels in the noise generated by light rail is announced.
“We are satisfied because it achieves the targets that we set during the public meetings in September 2023. We are talking about a combined reduction of 8 decibels (dBA),” says Francis Labbé, deputy director of communications at CDPQ. Infra, which will release a preliminary report on noise this Thursday.
In a hurry to make changes, the organization mentioned in December noise reduction targets for passing cars of “between 5 and 10 dBA”.
Last summer, measures taken by The Press with a sound level meter showed that the noise generated by the REM regularly exceeded the thresholds deemed acceptable by the authorities, particularly in the Pointe-Saint-Charles district.1.
The situation then concerned Montreal Public Health, but also many local residents, forcing the Caisse de dépôt to launch a campaign of sound tests between L’Île-des-Sœurs and Central Station. It was at the end of this that the decision to add measures was taken. Acoustic grinding has since been carried out on the rails, in order to polish the rails to reduce the noise of friction with the train.
Dynamic absorbers were also supposed to be added by December to reduce the propagation of vibrations, but the project was delayed and will not be completed until the spring. Work is always carried out at night, between 1:30 a.m. and 5:30 a.m., without affecting service hours.
“It will be completed this spring. After that, we can come back with other sound evaluations. We will make sure to finish the work,” said Mr. Labbé.
8 decibels less, but…
According to the report, acoustic grinding of the track, combined with “reprofiling of the wheels” of the train, makes it possible to reduce noise “by 4 to 5 dBA” depending on the sector. The dynamic absorbers, which are already partially completed in the Marc-Cantin (Pointe-Saint-Charles) and L’Île-des-Sœurs sectors, will ultimately result in a noise reduction of approximately 4 dBA.
However, the data included in the CDPQ Infra analysis show that the sound environment will remain high near the train.
At the edge of the track, it is in fact expected that the passage of the REM will generate between 84 and 88 dBA, depending on the sector, despite the grinding. With the addition of dynamic absorbers on the rails, the sound level would then be lowered to approximately 84 dBA consistently.
The scientific expertise on the subject is clear. According to the Ministry of Health, “prolonged exposure to loud noises, for example more than 75 dBA for 8 hours per day, can cause hearing loss.” “The body can also react to lower noise levels: sleep can be disrupted by noise of 40 dBA outside,” it says.
In the longer term, exposure to noise is associated with an increased risk of cardiovascular diseases “from a level of 55 dBA over a period of 24 hours”. At a threshold of around 80 dBA, holding a conversation is “difficult” and the perceived noise can resemble a noisy factory or restaurant.
Francis Labbé, however, reminds us that we must take into account the “multiplier effect” of noise. “What our experts tell us is that when we attenuate both the decibels at the vibration level and the more airy decibels at the bearing level, there is a multiplier effect which means that the noise felt can be attenuated by way more important than the actual noise,” he explains.
Last fall, CDPQ Infra mentioned that a drop of 5 to 10 dBA would be equivalent to “a drop in the level of noise emitted ranging from 3 to 10 times compared to the current situation”. This is because the relationship between the number of decibels and the perceived noise is exponential. In other words, a single decibel can have a big impact. “We must also remember that our measurements were taken a short distance from the rails,” adds Mr. Labbé.
No guarantees for other sections
At this stage, nothing indicates that the measures taken against noise between L’Île-des-Sœurs and Central Station will be reproduced on the other REM antennas which will be inaugurated at the end of 2024, namely those of Deux-Montagnes and of Anse-à-l’Orme, nor on the section towards the airport planned for 2027.
Not all sound environments are the same. On the Deux-Montagnes line, we are on the ground, unlike Griffintown, which is above ground with a structure mixing concrete and metal, so the resonance of the sound is not the same. We want to apply the right measures in the right place.
Francis Labbé, deputy director of communications at CDPQ Infra
At Action-Gardien, an organization that has mobilized in recent months to demand measures against noise from the REM, spokesperson Simon Paquette says he will examine the report before reacting. “We are going to do another survey in the neighborhood in the coming months to see if it is enough for residents. We really want to have everyone’s pulse before anything else,” he explains.
His group, which met with the CDPQ Infra teams in December, is asking in particular for another analysis to be carried out on noise, “but in a summer context”. “We know that the noise generated can differ depending on the season, so we think that it should also be done later this year,” adds Mr. Paquette.
1. Read “REM: “Noise is everywhere, all the time””