I moved to Montreal this year after living in Toronto my entire life. In my opinion, one thing Montreal truly does better is the Metro. It’s cleaner, there are more useful lines and even the colour scheme is cooler than Toronto’s subway. But beyond these features, there is a functional difference between the two systems: my hometown subway has steel wheels and steel rails, while Montreal’s cars roll along with rubber tires on concrete. Why did Montreal opt for rubber twelve years after Toronto chose steel? And all these years later, which has proven to be the better choice – environmentally and fiscally?
The ease with which two surfaces in contact with each other can be made to move is determined by the extent of friction between the surfaces. The “coefficient of friction” is a measure of the resistance to motion at the interface of two surfaces which is a function of the nature of the materials. It is easier to ski on snow than on concrete and easier to ski downhill on a steeper slope than on a gentle one.
There are two types of friction. Static – when stationary objects have an initial force you must overcome, as if you were to push a block from rest on a table. And kinetic – the resistance caused by moving objects, such as when the block is already sliding. Rolling wheels are an example of static friction because they’re pushing off the ground. Skidding is kinetic friction. So, the more friction between a tire and the surface it is on, the more it can “push” the train. This means that the rubber tires have more traction to accelerate and brake faster, and can function better on steeper slopes.
This ability to cope with slopes helps cut down initial costs of tunnelling. To help increase friction even more when breaking, trains have wooden brake shoes that have been treated with peanut oil. The wood prevents metal debris and dust, and the peanut oil makes the shoes fireproof. Rubber is softer than metal, so it can increase contact surface area by filling imperfections on surfaces. Rubber tires are also quieter, but if steel-on-steel is well-maintained it can provide a smooth ride.
Rubber tires would be dangerous with weather variance and ice – there are no snow tires – but this is not a problem since Montreal’s system is entirely underground. This, however, means that Montreal’s Metro can’t install air conditioning, because the hot air released from the trains would be trapped in the stations. Toronto’s system on the other hand is air conditioned and trapped hot air is not a problem since the network has a few stretches where trains run above ground.
Prior to 1966, when Montreal’s Metro opened for business, governments and suppliers paid much less attention to environmental footprints. Now, in 2022, environmental friendliness is all the rage. Which raises the question: which of these subway systems is more eco-friendly?
Rubber tires wear faster and must be replaced more frequently, meaning more waste. Trains on the Paris Metro – which pioneered the use of rubber tires and inspired Montreal’s design -- can run for 4,325,917 km for every $1 million in maintenance; Toronto’s steel wheeled trains can go for 8,991,405 km-- more than double. Montreal’s Metro requires approximately 2900 new tires every year – that’s a lot of old tires being discarded. When these tires break down, they also create airborne particulate matter that can remain in the environment for years, contributing to air pollution.
The friction between rubber and concrete is greater than between a steel wheel and steel tracks. This means that more energy is required to push Montreal’s cars forward than Toronto’s, but on the other hand, energy is saved from not having air-conditioning.
All in all, it is hard to say which system is more environmentally friendly. Toronto may have air-conditioning, but Montreal’s Metro can take you to places where you can get a proper smoked meat sandwich.
Haleh Cohn just finished her first year at McGill University and is interested in the health sciences.