March 23, 2023

Whether you’re driving, biking, or simply enjoying walking on the sidewalk, potholes are annoying, dangerous, and expensive. So get ready – as the spring thaw begins in much of Ontario, pothole season begins.

Over the years, CBC stations have told hundreds of stories about pothole problems in areas of Ontario and across Canada. Rapid road deterioration is already costing Canadians an additional $3 billion a year in vehicle maintenance, according to the Canadian Automobile Association.

As such, we should all be concerned that climate change could wreak havoc on our streets as cities prepare for more potholes, bumps, cracks and ruts.

Thankfully, engineers are working to create better, more durable and environmentally friendly materials, with innovations like self-healing asphalt and roads linked to artificial intelligence (AI) technology that can help predict where cracks and potholes will appear.

The Great Lakes Climate Change Project is a collaborative initiative by CBC stations in Ontario to study climate change from a provincial perspective. You can read some of the latest stories from the project here:

Canadian climate is perfect for potholes

Canada includes many different climates, but it just so happens that many of them already provide ideal conditions for potholes in the spring.

“Any time [temperatures] start to fluctuate between above zero and below zero, especially if these shifts are large, it’s basically pothole season,” said Scott Berry, road and traffic operations manager for the city of Kitchener.

“Whether it happens in January as a short week instead of a cold, or whether it happens during the traditional pothole season in March, April and May, that’s what contributes to potholes to a large extent.”

WATCH | Learn more about how potholes form:

Pit season is in full swing. Here’s how potholes form, and why they feel worse in some years than others.

This is known as the freeze-thaw cycle, and such cycles are common across Canada, said Ali Nazemi, assistant professor of civil and environmental engineering at Concordia University in Montreal.

Road problems occur when water seeps into the base under the top layer of asphalt and is subjected to freeze-thaw cycles. Water is the only known non-metallic substance that expands when it freezes and exhibits great strength in doing so.

When [water] expands, it starts to put pressure on the soil and infrastructure… it cracks the infrastructure,” Nazemi said. is happening, and the time is expanding.”

The more freeze-thaw cycles that occur, the more of these expanding ice-filled voids form under the top layer of asphalt and the larger they become.

“If this cycle continues, it will greatly increase the rate at which infrastructure wears out,” Nazemi said.

When it warms up and the ice melts, the top layer of asphalt will not be supported. When a truck or other heavy vehicle passes over the area, the asphalt can sag, exposing the void underneath.

And so a pothole is born.

Can potholes become a year-round problem?

Using new modeling techniques and data from remote sensing satellites, Nasemi was a senior author on a 2021 Journal of Hydrology article and a 2022 Nature Scientific Reports article that highlights some previously overlooked key climate change impacts in Quebec. He is currently applying these methods to the Canadian-wide model.

His study suggests that the transitional seasons before and after winter will become longer, meaning temperatures will approach freezing and the number of freeze-thaw cycles will threaten infrastructure across the country.

It’s a problem for cities and road users, said Scott Berry, city operations manager in Kitchener, Ontario.

“If that happens, then we will have a longer pothole season. It will not be limited to March, April and May. At some point, you might see pothole season creeping into February.”

Road with numerous cracks and large potholes.
Shown here, Barton Street in Hamilton East was named the worst road in Ontario in 2022 by the Canadian Automobile Association (CAA). (Bobby Christova/CBC)

There are many other ways that climate change will affect our roads, said Hassan Baaj, professor of civil engineering at the University of Waterloo and director of its Center for Road and Transportation Technology.

Extreme heat in the summer means more rutting as depressions in the asphalt are worn down by heavy truck tire marks. Increased rainfall can lead to flooding and damage to roads, while more intense exposure to sunlight degrades the quality of asphalt and leads to more cracks that water can filter through.

Of course, the best way to prevent additional damage to our roads is to reduce emissions. But since we’ve already experienced several decades of warming, researchers are looking for ways to mitigate the damage.

In fact, there is a “self-healing” asphalt.

Researchers have long found ways to produce “better” asphalt, Baai says, including changing the mix to make the asphalt more resilient, easier to produce, requiring less maintenance, or even self-priming.

“We are working to develop high-performance asphalt mixes that are highly resistant to various types of pavement wear.”

In recent years, sustainable design has become a major focus. This means that the innovations engineers explore must be sustainable and environmentally friendly.

As an example, Baaj cited “self-healing” asphalt, which is inspired by the biology of the human body.

There are numerous ways to do this. One involves introducing bacteria into the asphalt. When exposed to water, the bacteria produce calcium carbonate, sealing any cracks with limestone.

A city truck drives along a road with several potholes filled in.
In Thunder Bay, Ontario, potholes are common. Repair crews begin work in connection with the start of the pothole season. (Mark Doucette/CBC)

There’s also smart asphalt, artificial intelligence-driven roads that help predict and detect cracks long before they can be found on the surface, making repairs cheaper, easier, faster, and more efficient.

We have different tools built into different pavement layers. [and] transmitters that will collect data and send it to our team at the University of Waterloo for analysis using algorithms that we will create using artificial intelligence,” Baaj said.

“When we see patterns, when we see how things like high voltages and so on happen, we can connect those events that happen in the pavement and future events that happen later, like cracks that appear.”

Research is also underway to find more environmentally and climate friendly alternatives to traditional asphalt, which uses crude oil bitumen as a binder and is known to emit harmful air pollutants for years after installation.

A pilot project is under way in Thunder Bay in northwestern Ontario and several other cities in Canada to investigate the partial replacement of an alternative binder called lignin, a polymer mill, and abundant paper mill waste.

The skating rink rides on freshly laid asphalt.
A section of the road at the Thunder Bay Solid Waste Recycling and Treatment Plant was paved with new lignin asphalt as part of a pilot project. The city is measuring asphalt performance over the next few years. (Amanda Nason/City of Thunder Bay)

Baaj is also working to recycle old pavement to create new, more resilient asphalt without wasting old materials. He said it’s harder than you think, but it’s worth it.

“If we use recycled materials correctly, we will build sustainable roads that are as good as or even better than those that do not use recycled materials. Therefore, I do not create problems for future generations. My successors will have to deal with this. My kids will have to deal with this.”

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