Climate change and the rising cost of potholes

Spring in a city like Ottawa is also known as pothole season. The city spends millions on repairing hundreds of thousands of potholes every year and experts say with a changing climate, it's only going to get worse.

Experts say pothole problems will only get worse with climate change

Potholes at the intersection of Somerset Street West and Bay Street in Ottawa in February 2018.
The City of Ottawa has filled more than a million potholes since 2018. (Andrew Foote/CBC)

After a snowy winter paired with temperatures that kept the Rideau Canal Skateway closed for the first time ever, people in Ottawa are beginning to see signs of spring.

Rising temperatures also lead to crumbling roads that can resemble the surface of the moon. Driving your car feels like riding a mechanical bull.

Anyone who lives in Ottawa knows spring is better known as pothole season. 

Fluctuating temperatures create a destructive cycle of expansion and contraction of brittle, frozen asphalt, and more powerful rays of sunshine melt ice that has, for weeks, concealed cavities in the road.

Ottawa has 6,000 kilometres of roadway, each one subject to the nearly 80 freeze-thaw cycles the city sees on average each year. Crews fill hundreds of thousands of potholes every spring, 17,435 so far this year, according to city staff.

Roads built without considering climate change

Some experts say the problem is only going to get worse.

"We built these roads many years ago without considering the climate change scenario," said Kamal Hossain, a professor of transportation engineering at Carleton University.

Kamal Hossain, a professor of transportation engineering at Carleton University in Ottawa, stand at the corner of Greenbank Road and Cappamore Drive in the city's south end.
Kamal Hossain, a transportation engineering professor at Carleton University in Ottawa, studies road construction and maintenance. (Nicole Williams/CBC)

Crews have traditionally used a specific glue for asphalt but that material is highly sensitive to heat. As Ottawa experiences hotter temperatures, it softens the asphalt and ultimately weakens the road further, he said.

The City of Ottawa is well aware of this. Staff produced a comprehensive report last spring listing the many risks to city infrastructure and to people's health as the weather becomes warmer, wetter and stormier. High up on the list: Ottawa's roadways.

"Road materials are not rated for the extent and duration of the heat events projected," the city's report on climate change vulnerabilities states. Winter freeze-thaw events "are particularly damaging" to roads and sidewalks, it said, because they cause cracking, heaving, potholes and rutting.

Pothole price tag growing

Crews already fill hundreds of thousands of potholes every year, more than 1.1 million in total since 2018. As the cost of labour, materials and the expansion of Ottawa's road network grows, so too does the cost of repairs.

The city's budget for asphalt repairs and maintenance has steadily climbed over the last five years, and that doesn't even include the more costly jobs where entire roads are repaved.

Road users absorb costs, too, especially those who hang onto older vehicles to save money, which are more prone to damage, said Julie Beun of the Canadian Automobile Association (CAA) division for northern and eastern Ontario. 

Whether it's a blown tire or damaged (possibly dislodged) bumper, potholes can cost a vehicle owner up to $6,000 to repair.

"We've got like 34,000 kilometres of what we've deemed as poor or very poor roads in Ontario, and so somebody's going to come to grief no matter how they move," said Beun.

Solutions are too expensive, says city

The solution — changing the way roads are built — requires significant investment, Hossain explained.

Some jurisdictions, including Canada's three territories, use concrete to enhance the durability of roads, but it is more costly than laying down asphalt.

The U.S., which has a Federal Highway Administration, spends hundreds of millions of dollars each year on researching road construction and sustainability. That is "a very unfortunate part that it is missing in Canada," said Hossain.

For the City of Ottawa, the last 10 years has been a period of trial and error for road building.

In 2018, contracts to asphalt suppliers were cancelled after a 2017 audit found the materials fell short of required standards for fixing roads and potholes.

The city continues to search for a fiscally responsible way to fix the issue in the long term, according to Coun. Tim Tierney, who chairs the city's transportation committee.

Tierney, who has been on city council for more than 12 years, recalled a time when crews tried using beet juice to improve road traction — unsuccessfully.

There is no room in the budget for concrete, he said.

The Python 5000 first cleans out the hole in the pavement before it fills them with asphalt.
The city will deploy four Python 5000s later this March. The machine first cleans out a hole in the pavement before filling it with asphalt. (CBC)

Still, he acknowledges the city already spends a lot of time and money maintaining its roads. In 2019 Ottawa bought two Python 5000s — $400,000 machines that automatically clean potholes, fill them with asphalt, and tamp them down. 

Tierney said there will be four Pythons as part of Ottawa's repair fleet as of late March.

"As industry and technology gets better, hopefully we'll have a better solution," Tierney said.


Nicole Williams is a journalist for CBC News based in Ottawa. She has also worked in P.E.I. and Toronto. She is part of the team that won a 2021 Canadian Association of Journalists national award for investigative journalism. Write in confidence to

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