QUESTION: "How do potholes form?"

by User Not Found | Mar 26, 2014

Welcome to One Big Pothole's #AskAPothole series! The place where you ask questions about potholes and we dig up the facts and share them with the world.

As it's day one we'll start with a found question. This might be the most frequently asked pothole-related question on Twitter. Asphalt and transportation experts have provided huge amounts of information on the topic, so rather than build an answer from scratch we'll see what they've already got cooking.  

The Ingredients:

According to the Internets, it requires two things.

First, potholes can't exist without asphalt. US Department of Transportation documentation associates "Potholes" exclusively with asphalt pavement distress.

Second, according to the Asphalt Institute, potholes are the result of pavement distress. In the organization's Asphalt Pavement Distress Summary, the listed causes of pavement distress include (but are not limited to):

  • Excessive loading
  • Poor drainage
  • Old mix
  • Low traffic volume
  • Frost heave
  • Vegetation
  • Asphalt shrinkage
  • Daily temperature cycling
  • Heavy traffic
  • Dust
  • Oil
  • Dirt
  • Rubber
  • Water
  • Turning vehicles
  • Utility cuts
  • Patch failure
  • Materials failure
  • Improper installation

More recently, during a regional Asphalt Conference & Equipment Show, a presenter showed slides indicating that merely exposing asphalt to air and water causes asphalt binders to fail. As does light from the sun.

If true, that would mean that asphalt pavement has potholes quite literally baked in from the moment the sun rises on the first day.

The Recipe:

For expediency, let's limit the ingredients to one of the more common Pothole Season situations. Take a bunch of asphalt pavement, water and traffic and mix them together. Then vary the temperature above and below the freezing point and watch what happens. Here's how the Michigan Department of Transportation explains it:

There's your answer! 

Now that we've got that sorted out, who wants their own pothole question answered? Follow us and tweet your questions to @OneBigPothole or use the #AskAPothole hashtag. 

Stay safe out there!

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