The most effective way to mitigate noise is at the source. The largest reduction of noise from train operations will come with the electrification of the rail network, but noise walls are a helpful tool to mitigate noise in communities where further measures are needed.
The biggest objective of Metrolinx’s GO Expansion project is to build a transit network that connects people across the entire region.
That means new tracks, expanding bridges, and more trains.
More GO service means customers will be able to depend on the frequency of trains rather than needing to check the schedule to ensure they are at the station on time.
But it also means things could get a little noisy for the thousands of residents and businesses near GO tracks and stations. As part of the planning behind GO Expansion, Metrolinx has studied exactly how more trains will lead to more train noise, and how to best keep it to a minimum.
These assessments are part of the GO Expansion Transit Project Assessment Process (TPAP). You can check out this recent Metrolinx News story on the most frequently asked questions regarding the latest TPAP, which addresses the electrification of the GO Network, as well as the most recent TPAP materials.
Metrolinx can mitigate noise in different ways, but the transit agency’s studies show the most effective form of noise mitigation is to address it at the source – the trains themselves.
One significant way to reduce noise is using electric instead of diesel-powered locomotives. The bulk of future service increases will be delivered by “going electric”. Aside from being able to accelerate and decelerate faster and stay at top speed longer, electric trains are significantly quieter than diesel trains at low speeds, when starting or stopping, and when idling.
Going electric isn’t the only way to reduce noise at the source. Metrolinx’s train silencer program will install exhaust noise silencers on existing and future Metrolinx diesel locomotives, which will decrease the sound from these trains by an estimated 3 decibels along the corridors. Metrolinx is also reducing engine idling and switching from 12-car to 6-car trains during off-peak periods wherever possible.
Other measures to reduce noise at the source include constructing grade separations, so trains can move much more seamlessly through urban areas. Grade separations mean the trains do not need to slow down at intersections, reducing the noise that comes with deceleration and acceleration. By making improvements to tracks and switches and installing ballast mats underneath new track and switches, Metrolinx can also reduce vibration and noise.
However, there’s more than one strategy to reduce noise impacts for the nearby communities than just at the source. In instances where reducing the noise at the source won’t do the trick, Metrolinx will look to reduce noise at the receptor – i.e., your ears (or your dog’s ears). This usually means putting a barrier between you and the noise, and one type of barrier is a noise wall.
What is a noise wall?
Noise walls are external structures placed in strategic locations to absorb the noise and to deflect it away from nearby receptors. Noise walls vary in design, but in the context of Metrolinx projects, they’re usually around 5 metres tall and made from a composition of concrete and other materials like wood shavings.
How and when noise walls are built
If and when noise walls get built depends on the development of different Metrolinx projects and their noise implications for affected communities. Right now, the transit agency is starting work on expanding a section of the Barrie GO Corridor in King Township and can use that as an example of when noise walls come into the picture.
The project in King Township is preparing that section of the Barrie GO Corridor to add an additional track. The additional track will allow Metrolinx to add two-way, all-day service to this corridor.
The first phase of this project involves preparing the corridor (i.e. vegetation clearing, utility work and grading). The second phase also involved preparing the corridor (grading for the future second track, drainage upgrades, utility relocations, and retaining walls), as well as upgrades to King GO station, and building noise walls.
The first phase of the project is already underway, but the second stage of the project is in procurement. So, while the project has started and crews are busy working on phase one, the specifics for the work in the second phase – including details on those noise walls – aren’t available quite yet.
Those details will come later once a contractor is selected for the second the stage of the project.
Deciding where to build noise walls
Locations for noise walls are based on studies identifying the level of projected operational noise due to increased service.
To study this, Metrolinx used predictive modeling to compare existing and future noise and vibration levels associated with the future train service and the proposed new infrastructure.
Receptor areas around the tracks are identified, and certain areas are categorized as sensitive, based on the land use for that area.
You might be able to guess what would be included as a sensitive area: places like residences, schools, libraries, and daycares. Future noise levels are predicted at these receptor locations and determined whether they exceed a threshold that is set by the provincial protocol for noise assessments.
To decide the locations for these walls the transit agency looks at two factors: where noise will increase and where building barriers would benefit the most people in the area. Noise walls must reduce noise exposure by at least 5 dBA (weighted decibels) in order to be effective, as required by the provincial protocol.
Under the provincial protocol for noise assessment, Metrolinx is recommending 30km of noise walls as part of the GO Expansion program and is already contracted to build 27km of noise walls along the Barrie and Stouffville corridors. This brings the total length of noise mitigation to approximately 57 km across the GO rail network, including 18 km of additional noise walls in communities currently experiencing high background noise.
By making strategic decisions about where to construct noise walls, Metrolinx can mitigate noise for more communities while also delivering more frequent service with GO Expansion.
Read more about noise mitigation by checking out Metrolinx’s Noise and Vibration update report under the GO Rail Network Addendum in the Transit Project Assessment Process here.
Story by Allie McHugh, Metrolinx community relations specialist