The Road to Spring Is a Bumpy One

Engineers get help at winter's end in battling the baneful pothole

It's pothole season.

If any seat-jarring, tire-eating hole is going to open up on your way to work or the supermarket, this is the time it's likely to happen. Spring is when potholes blossom, particularly in the northern states. It's also when road engineers turn again to fix the weather-caused craters in America's roadways.

This spring, engineers are getting some help. New technology and better methods have been developed to smooth streets and highways. Road crews across the United States are beginning to employ everything from fibrous asphalt to robotized hole-patchers in the bumpy battle.

Potholes form because water seeps into the soil underneath the roadway. The wetter that soil gets, the weaker it becomes - until it can't support the pavement. Then, when heavy traffic runs over that spot, the roadway flexes more than normal and, eventually, breaks. A pothole is born.

Consumer pocketbooks should benefit from the new combative methods. Rough roads not only force more car repairs but also lower overall gas mileage. "That's a hidden tax," says Lynne Irwin, director of the Local Road Program at Cornell University in Ithaca, N.Y. If it costs 25 cents to run an average car over a mile of new, smooth highway, it costs roughly 35 cents to drive the same vehicle over a mile of bumpy road, he estimates. And that figure doesn't count highway and related taxes.

"It may be slow progress, but I think we're making progress," says Charles Churilla, chief of the pavement-performance division for the research office of the Federal Highway Administration (FHWA) in McLean, Va.

Better patching technology

Perhaps the most noticeable improvement in recent years has come in pothole-patching technology. In the old days, crews got out in the spring to "throw and roll" - throw asphalt into the biggest holes and roll over it with their truck to press it down. The asphalt didn't stick very well, but crews hoped the fix would last until summer, when road crews could get in and make a permanent patch. Often, analysts say, the patch wouldn't last two weeks, let alone two months.

Over the past several years, however, private companies and state transportation departments have developed new asphalt mixes, some of them impregnated with fibers that are more resistant to water and stick better to the road even in cold weather. The results are remarkable.

While these patches aren't designed to be as good as permanent, summertime repair, they can last years. As part of a now-ended research program, the FHWA tested the new materials in more than 1,000 potholes in 1991 and found that some 60 percent of those patches are still in place.

But it's expensive

The drawback: the new materials are typically two to three times more expensive, and local maintenance crews are reluctant to change. "We're in the process of educating our people," says Ron Brown, materials engineer for the New York Department of Transportation, based in Albany. But "they're so used to going out and fixing the same holes two or three times."

New machinery is also helping the cause. By using compressed air to shoot out the stone-and-oil asphalt mix, road crews can better compact the soil underneath the pothole patch - an important plus. State crews in charge of Pittsburgh and the surrounding district use six trailer-type units that can be towed by a dump truck to fix potholes. The machines can shoot out stone at about 80 miles an hour.

Other areas of the state are experimenting with a robotic version of the machine, which reduces the pothole-patching crew to one person, a driver, who controls the entire process.

Reducing labor costs is a big step, but the robotic machines are at least six times more expensive than the trailer units, says Bill Sacco, assistant district engineer in charge of maintenance for Pennsylvania Department of Transportation District 11. So his district is sticking with the mobile units for now.

Some roads are rougher than others. Some states have better roads than others. In general, rural interstate highways have the fewest potholes and other bumps and cracks; principal arterial streets in cities have the most, according to FHWA statistics. Ohio has the least potholed highways; Pennsylvania, the most, according to a survey of 4,000 truckers by Overdrive magazine last fall.

Of course, patching potholes is only an interim step. "A pothole is a symptom of a road that's come to the end of its usable life," says Mr. Irwin of Cornell University.

The older the road, the more frequently potholes appear. If supervisors aren't careful, they can spend more money patching an outdated road than rebuilding it completely. Here too, engineers have made strides by developing asphalt and concrete specially formulated to handle the specific region's heat and cold.

The problem is aggravated in northern states by the cycles of freezing and thawing during the early spring. The resulting holes pose hazards not only for cars and trucks, but for anyone using the road, especially bicyclists.

Knapp Hudson, a chemical engineer and tandem-bicycle enthusiast in Portland, Maine, has had to switch to heavier tires. Speaking from experience he says, "The cyclist is much more vulnerable."

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