How potholes happen
An unusually snowy winter has left behind an obstacle course of tire-eating, suspension-twisting potholes. What causes good roads to go so bad? Blame physics and the area’s up-and-down temperatures. By Sohail Al-Jamea and Bonnie Berkowitz. Read related article.
Potholes begin when rainwater or melting snow seeps through cracks in the asphalt.
The temperature drops, and the water freezes and expands. Sometimes, the ice breaks the pavement immediately. Other times, the damage is temporarily hidden in the supportive subbase below.
When the ground warms, the ice melts, softening the road and leaving pockets under the pavement that collapse like mini sinkholes under the weight of cars.
Tires kick out the crumbled remnants, and presto! Another predatory pothole lies in wait.
Sources: Virginia Department of Transportation, AAA. Special thanks to cooperative pigeons at the McPherson Square Metro station. None were harmed in the making of this video.