How experts reduce noise and vibration on the Ontario Line
Metrolinx experts discuss options available to deliver a subway that respects surrounding areas.
Jun 9, 2020
While all forms of transit create some noise and vibration, Metrolinx experts are working to reduce their impacts along the Ontario Line.
To reduce the impacts, you have to start at the source – with the train itself.
When you say “train,” many people picture a more traditional large train that has a diesel engine – much larger and noisier than an electric train.
“The Ontario Line will be electrified and the noise profile of an electric train is unlike a heavy rail train,” said John Potter of the Metrolinx Design Division.
“We will review all options that reduce noise and vibration, and ensure we get the right combination for the Ontario Line.” – Maria Zintchenko, a project manager at Metrolinx.
In all modes – whether accelerating, decelerating or cruising along – electric trains are quieter than their diesel counterparts.
The next step in reducing noise and vibration at the source is to look at the contact between the wheels and track.
Older tracks had joints that created the famous clickity clack sound.
“If you have joints, then you have something that is uneven, so the wheels produce noise as they roll over them,” said Maria Zintchenko, a project manager at Metrolinx.
New lines are typically built with continuously welded rail, to create a track that is largely without joints.
Metrolinx also has many other tools at its disposal for staying within regulated noise and vibration standards.
“We will review all options that reduce noise and vibration, and ensure we get the right combination for the Ontario Line,” Zintchenko said.
Picking the right tools to mitigate noise and vibration is an evidence-based process.
“Once we do the assessment modelling and we know the results, we will be in a better position to say what measure or combination of measures is most appropriate,” she said.
As the Ontario Line plan is refined, Metrolinx experts will have several tools to choose from, including these:
- Rail dampers – These are devices attached to the sides of rails that reduce noise at its source. They minimize vibration within the rails when trains pass over them. Well established in the rail industry, dampers work by using a spring mechanism with steel and rubber components to dissipate vibration energy, which would otherwise radiate from the rail as noise.
- Resiliently supported rail ties – They reduce vibration by using an under tie pad made of elastic material that prevents direct contact between the ties and the base structure or ballast – the crushed rock that forms the track bed upon which rail ties are laid. Similar to rail dampers, they are another proven mitigation tool.
- Ballast mats – Installed beneath the ballast bed (the crushed rock mentioned in the last point), they provide a continuous layer of material that prevents vibration from being transmitted into the ground. The mats also improve longevity of ballast material and can reduce maintenance needs. They are already in use in parts of the Metrolinx-owned rail network.
- Floating slabs of concrete – Supported by isolation pads or steel spring mounts, they can effectively reduce vibration by absorbing energy. This works because they are separated from the primary tunnel structure or base slab constructed on the ground. The TTC was the first system in North America to use this technology with the Yonge Subway line.
- Highly resilient fasteners – Clips hold the track onto the under-rail foundation. They are specially designed to be compressible to absorb vibration energy. These have been used successfully on the TTC subway network.
- Noise walls – These barriers block the sound path between source and receiver. They can be designed with a combination of solid and transparent panels, and have been installed across many parts of the Metrolinx rail network.
Even after the line is built, the work of reducing noise and vibration will be ongoing. Once the trains are running, there will be continual track and vehicle maintenance, combined with timely monitoring and inspections. Finely tuned moving parts combined with well-maintained permanent infrastructure will ensure trains operate as smoothly and unobtrusively as can be.
Of course, Metrolinx knows that it’s also very important to control the impact of noise and vibration during construction.
Before construction starts, Metrolinx will establish a comprehensive program to inform people about the project’s scope, schedule, noise and vibration management strategies, and complaint resolution protocols.
Metrolinx typically implements a construction Noise and Vibration Management Plan. It will take practical steps to reduce impacts by keeping equipment well maintained and fitted with muffling devices, using equipment and methods that minimize vibration, and coordinating construction schedules so that noisy operations do not occur simultaneously.
Metrolinx will monitor noise and vibration throughout construction, testing to see if more measures are necessary.
And of course, any public comments received along the way will be addressed in a timely manner.
Metrolinx is working to make sure the Ontario Line becomes a valued part of the communities it reaches—not only by providing much needed transit options, but by ensuring the right tools are in place to address any impacts.
Because we know how you remember the neighbour with the motorcycle used as a weekend alarm clock.
by Mike Winterburn Metrolinx News senior writer