What Causes Potholes?

Most roadways are built in layers, starting with compacted earth and gravel to form a solid foundation or base. All of these layers are covered with asphalt, which is a gooey blend of tar, oil byproducts, curatives and aggregate gravel. In an ideal setting, this layer of asphalt repels rainfall and snow, forcing it into drains or the shoulder of the road.

Potholes begin after rain or snow seeps into the soil below the road surface. The moisture freezes when temperatures drop, causing the ground to expand and push the pavement up. When the temperatures rise, the ground returns to normal level but the pavement can remain raised. This creates a gap between the pavement and the ground below it. When vehicles drive over this cavity, the pavement cracks and falls into the hollow space, leading to the birth of another pothole.

Potholes can cause significant damage to a car's suspension system or tires if the driver fails to avoid them. Potholes can also fill with water, obscuring any other hazards they may contain. Even in places where the air temperature rarely falls below freezing, excessive rainfall or flooding can also cause potholes to form.