Crash Course in Potholes: The How, Why, and WTF

*Disclaimer: I do not work for the DOT or for any entity involved in road or highway repair. I am just a fan of fixing things right the first time. 

Billions of Dollars, Thousands of Lives

According to the American Automobile Association (AAA), potholes cost American drivers approximately $3 billion a year, and are involved in over 3,000 fatalities. That’s not a problem, that’s a plague.

But fixing the pothole problem on America’s roads isn’t as easy as most people think, and it’s a problem that comes back year after year. Simply filling in potholes is not enough of a solution, but to understand the magnitude of the problem, we have to look what causes these car craters and methods used to repair them.

Before pointing our righteous fingers in the quick-blame game, we should remember that the men and women repairing these potholes are men and women, with lives, homes, and health. They are out there pouring hot asphalt into these craters in 100 degree summer weather and tossing shovels of stinking rock and tar into them in below-freezing winters.

Whether or not the paycheck is nice isn’t the question; it’s a hard job for anyone to do. We should also remember that asphalt is a proven carcinogen, made even more dangerous when heated, and the men and women of the DOT are spending their entire day working with it.

So how about tossing them a shovelful of empathy?

Pothole Problem: From Bad to Worse

Our ever-increasing pothole problem shouldn’t be a surprise to anyone. Much of the state and county road system in the United States is around 100 years old. Today, 222 million people in the United States possess driver’s licenses; that’s more than twice the total number of US citizens when most of roads were made. Our surprise shouldn’t be that the roads are falling apart but that they have lasted this long!

Our interstate highway system largely sprang out of the Eisenhower-era of the 1950s. On these roads, contractors used mostly concrete, not asphalt, and utilized advanced construction techniques that allowed stronger surfaces with better drainage. Potholes aren’t rare, but they’re not nearly as common.

State and county roads, however, are made of asphalt, a sticky and flexible mixture of petroleum aggregate. 70% of the world’s asphalt is used in road construction, and can be applied either cold or hot. Asphalt has many advantages as a construction material. It’s relatively cheap and abundant, and can be easily cut through and removed if workers needed to access areas below ground (such as a sewer system). Since it is semi-viscous, it lends itself to virtually any surface contour as well.


But that flexibility has a heavy cost. If roads have poor drainage, either from construction errors or disrepair, water pools beneath the asphalt, between the road and sub-base. In warmer climates this isn’t as heavy a concern for roads, which is why asphalt in the subtropical climates of the United States tend to last longer.

But in temperate climates, such as those of Indiana, water freezes every year. Freezes and thaws, freezes and thaws. In terms of erosion, nothing on Earth is more destructive than water, and its property of expanding and contracting during this process is water at its most destructive.

As illustrated in the above graphic (and the image below) given enough expansion and contraction, asphalt will show the telltale signs of subsidence in the sub-base, manifesting on the surface as alligator-cracking or alligatoring, for its cosmetic similarity to the skin of a alligator. No matter the name, it ultimately means the same thing: road surface failure.


Road crews can repair these cracks, but it’s a temporary measure at best. At worst, it’s a waste of time. No matter how it’s repaired, the end result will be a pothole, and the only solution is cutting through the damaged surface, removing the chunks of hardened asphalt, assessing the sub-base condition, and repairing the fault completely.

Honestly, for a problem area that might last for months or even years longer, this is not typically a priority, since larger, more potholes are likely in need of repair.


Asphalt used in road repair is not exactly the same as that which you’d buy at a home improvement store. Cold patch asphalt, sold in buckets or bags on the shelves of Home Depot or Lowe’s, can be used to fill virtually any pothole, but most DIYers take its ease-of-use for granted. Long-term, heavy-use repairs cannot be performed in the same way as driveway repairs (although crews do use cold patch asphalt in certain circumstances).

Non-DIY Pothole Repair

These are the repairs you WON’T do at home.


The least expensive and most common repair, this is the method most often used by crews not because of its durability but its efficiency. Crews can roll down the length of a badly-damaged road, leaving it partially open for traffic flow, and repair a large number of potholes in a short time.

However, throw-and-roll fixes rarely last long, and it’s common to see the same hole fixed two or times in the same year, especially in areas of heavy traffic. It’s also the most common repair conducted in dangerously cold or hot weather.

Workers “throw” asphalt into the hole, sometimes removing loose material but often leaving broken asphalt and standing water. The hole is filled and then overfilled, and then another vehicle (or the same one) compacts the patch with its tires until there’s a slight crown on the surface, usually no more than a 1/4 to 3/8 of an inch, to allow for future subsidence.

Semi-permanent repairs

If weather or schedules allow better repairs, crews can supplement throw-and-roll repairs with several further steps. First, before filling, any water or debris is completely removed from the pothole. Next, a pavement saw slices through the asphalt, neatly squaring off its jagged edges.

After being filled, the hole is flattened using a vibratory-plate compactor, sort of the heavy-duty version of a handheld tamper. This allows the asphalt aggregate to seal and settle, leaving behind a firm surface.