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Cracked and pothole-ridden pavement.

Filling the Gap: Where do Potholes Come From?

Pick a road – any road -- in Canada and chances are you’ll drive past incredible beauty, vibrant cities and bustling communities. But scratch the surface of those roads and it’s what’s underneath that counts when it comes to safe driving.

Potholes, crumbling verges and cracks like those CAA Members nominate for the annual Worst Roads campaign aren’t just seasonally minor annoyances – they’re costing Canadians $3 billion in vehicle costs annually.

Yet, building road infrastructure in a geographically diverse province like Ontario means considering a vast number of variables, from temperature, terrain and use to location and materials use, says Dr. Doubra Ambaiowei, Technical Director for Ontario Road Builders’ Association (ORBA) and Ontario Asphalt Pavement Council (OAPC).

“Under-designed pavements will deteriorate following traffic opening due to the inability to withstand excessive stresses,” he says, as well as factors like moisture-related damages from water entering cracks, a general lack of preservative or timely routine maintenance.

Tire in pothole.

Dr. Ambaiowei, an expert in road building materials, estimates that a well-designed asphalt concrete road – which accounts for 95 per cent of Ontario’s roadways – don’t start to show signs of deterioration within the first five years of use. Even so, the annual pothole season can test even the best laid surfaces because, by their very nature, they start out so small, they’re hard to detect before they become a problem.

 “Potholes often start out as faint microscopic cracks on the pavement surface. A pothole can develop from these tiny cracks if a pavement is not maintained for common distresses. Bad weather, poor drainage and heavy traffic further cause loosening and wearing of the pavement surface,” he explains.

“While most pavement distresses are noticeable on the surface, root causes stem from the foundation structure. Only a combination of solid structural pavement and timely preservation activities can completely avoid the formation of potholes and development of other distress types,” he adds.


Slowing or stopping pothole development is something of an exact science, involving asphalt mix, best practices during construction and maintenance or rehabilitation that ensures the road’s long-term performance. In Ontario, asphalt pavements and materials are designed, tested, inspected and placed in accordance with applicable versions of the Ontario Provisional Standards and Specifications (OPSS), and in conformance to individual municipal requirements.

Dr Ambaiowei says that both ORBA and OAPC actively pursue their mandate of improving and enhancing the quality and performance of asphalt pavements, not just for road safety, but for the economy, as well. “Roadways are vital to economic and social development. They are the backbone of our transportation infrastructure system that ensures goods and services, essential workers and ourselves get to where we need to be,” he says.

“Our network of road infrastructure is considered the most important of all public assets.”

Dodging potholes? Cast your vote for the Worst Road in your community. Every vote is a chance to win FREE gas for a year.