The University Record, April 11, 1994

Rough roads can cost motorists big bucks

By Bernie DeGroat
News and Information Services

The advent of spring brings warm weather, blooming flowers and the baseball season, but it also means potholes, pavement upheavals and rough roads.

“People blame the highway departments for having poor roads, but we need to recognize that, in Michigan, the environmental conditions are rather adverse to the health of the road system,” says Thomas D. Gillespie, a researcher at the Transportation Research Institute.

Gillespie, who helped create the International Roughness Index for roads, says water is the main culprit of damaged roads.

“In effect, the roads experience some of the worst environmental conditions in which the road freezes, accumulates moisture due to snow and ice, and then begins to thaw,” he says.

In addition, the temperature alone can wreak havoc on roads as asphalt and concrete contract when the mercury plummets below freezing, Gillespie says. “The surface of a road that has been warm and then gets cold will try to shrink while the rest of the road hasn’t yet, which opens cracks on the surface, and if it’s a concrete road, individual slabs will try to curl.”

Salt corrosion, he says, is another environmental factor detrimental to roads, causing rust to metallic structures such as bridges and to concrete road materials with metal reinforcing bars.

“The problem is that rust is very powerful and generates tremendous compressive stresses,” Gillespie says. “This happens both with bridges and regular road surfaces.”

But the state’s winter climate is only partly to blame for deteriorating road conditions. According to Gillespie, roads also are damaged from the stresses imposed by traffic, particularly heavy trucks, which comprise as much as 10 percent to 20 percent of traffic volume on major highways.

“Road-damage models used by our highway engineers indicate that one heavy tractor-semi-trailer, which can weigh up to 80,000 pounds, can do as much road damage as 10,000 to 20,000 cars,” he says.

He adds that the quality of materials used in building roads and methods of water drainage also play a role in the durability of roads.

Gillespie says that damage to vehicles caused by rough roads can more than double a motorist’s routine maintenance and repair costs.

“People at times have had the experience of hitting a pothole big enough that it actually bends the wheel of the car,” he says. “Aside from that, rough road conditions will increase the accumulating damage to a car—they can wear out shock absorbers, contribute to wear of tires and increase fuel consumption.”