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Pot Holes

A car avoids potholes in Auburn.

The Citizen file

It is hard to believe that there was a time when roads in the United States were considered to be in worse condition than they are today; however, they were. Poor road conditions existed because they lacked proper construction, maintenance and drainage. According to the Cornell Local Roads Program, an association of bicycle riders called the League of American Wheelman in 1893 helped change the condition of the roads. By 1904 approximately 7 percent of the U.S. roads were considered improved as they were graded and smooth. The improved roads were actually gravel!

As Rural Free Delivery of mail increased along with an increase in the use of cars, more pressure was placed on governments to build better roads. The condition of today’s roads has improved greatly over the past 100 years, yet our roads still remain behind some of the industrialized world.  According to Statista (https://www.statista.com/statistics/268157/ranking-of-the-20-countries-with-the-highest-road-quality/) the U.S. ranks 10th out of 20 countries in 2017. The U.S. still has plenty of opportunities for improvement. Many of the problems we experience today are related to water management or drainage.

The CLRP estimates that highway agencies spend more than 25 percent of their budget on drainage. The results of poor drainage on road surface can be seen as rutting, cracking, erosion, washouts, heaving, flooding and potholes.  Potholes are probably what most drivers fear.

According to the calendar we have made it to spring, which many consider pothole season. So where do potholes come from? Potholes are caused by the expansion and contraction of water under the pavement. You might remember from grade-school science class that when water freezes it actually expands. You can see this happen every time we place water in trays to make ice cubes. If you look closely you can see a bump that develops in the top of the ice cube, this is the result of expansion.

The same expansion of water, as seen when making ice cubes, happens during a freezing period under the road surface if water has gotten under the road.  The expansion of the water when frozen weakens the pavement surface and can actually bend and crack the pavement. When the thaw comes and the ice melts, the water contracts — leaving the pavement weakened and unsupported, resulting in gaps and cracks of the pavement surface. These gaps and cracks allow more water to get under the pavement surface. When this occurs, especially over several freeze thaw cycles, the pavement continues to weaken and cracks open. 

As we exit winter, the roads actually thaw from the top down. The road shoulders can remain frozen even when the road is thawed because of different materials used in their construction. The worst-case scenario, thus making it ideal for pothole formation, is when an unfrozen layer is over a frozen base and the shoulders are still frozen. One way to remedy this situation and protect roads is to temporarily post roads to restrict heavy vehicles. The time period to protect the roads from heavy traffic is relatively short and it may help reduce roads from failing during the spring thaw, but may not be popular with local users.

As we now know, potholes occur when asphalt pavement fails from water in the structure under the asphalt weakening the subsoil structure. Traffic moving over the affected area creates stress and breaks the now poorly supported pavement surface. Potholes can also occur in dirt or gravel roads and are also caused by water trapped below the surface. To avoid potholes, it is important to maintain or improve the quality of underground drainage. This costs money in already stressed highway department budgets.

Once the road surface is weakened the weight of traffic passing over the weakened road surface displaces the materials under the surface. As the surface becomes displaced, the result is a pothole which seems to appear overnight! 

According to a New York Daily News article dated Feb. 26, 2014, New York City drivers spent on average $2,300 a year due to damage from potholes. Damage from potholes can impact the car’s suspension and steering components along with damage to the wheels and tires. Keeping your tires properly inflated can help reduce damage from potholes plus proper inflation protects the rims should you hit a pothole.

With pothole season here, find your tire pressure gauge and check your tire pressure, slow down, and take extra caution when approaching crews working on the roads addressing potholes to make sure you and your car are safe.

Judy Wright is a senior resource educator with Cornell Cooperative Extension of Cayuga County. For more information, visit cce.cornell.edu or call (315) 255-1183.

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