Potholes, ruts, crumbling asphalt mark interstate highways. Heavier trucks, new tires, and higher speed limit add to problem

Millions of Americans will hit the road this Labor Day weekend - but many will find the nation's premier, interstate highways in a crumbling state of disrepair. In many states, poor roadways are making a mockery of the higher 65 mile-an-hour speed limits in rural areas allowed this year by Congress.

An 8,000-mile, cross-country trip during the past month found potholes, bumps, and cracking surfaces to be widespread, especially in about a dozen states.

Highway engineers in some regions report they are fighting an uphill battle because of heavier trucks, greater traffic, and higher speeds. In some states, greater truck weights are wearing out road surfaces at a faster-than-expected rate.

More than one mile out of every 10 of the 43,593-mile interstate system is in poor condition, according to the most recent figures released this summer by the Department of Transportation.

Congress - recognizing the problem - is pouring billions of dollars into highway rebuilding through steeper gasoline taxes.

Experts say the higher spending has begun to pay off. Federal officials report that, after years of deterioration, they have recently measured a small improvement in the overall condition of the interstates.

That is little comfort, however, to anyone who makes the jarring trip across eastern Colorado via I-70. A 100-mile drive on a recent night was akin to a trip on ``Mr. Toad's Wild Ride'' at Disney World. Cars bounced and shuddered on mammoth potholes. As rain pounded against windshields, tires sloshed through inch-deep water in ruts in the crumbly pavement. Lanes were hard to follow because of worn-out markings. New signs advising ``Speed Limit, 65 MPH'' seemed like a bad joke.

While federal officials say that sort of thing is becoming less common, not everyone agrees.

In North Dakota, chief highway engineer Ray Zink describes the improvment this way: ``Our roads today are getting worse at a slower rate.''

In Colorado, Carl Sorrentino of the highway department says ruts have become a major problem, even on concrete roads, because of higher truck weights allowed by Congress - 80,000 pounds today, compared with 73,280 pounds in earlier years.

Mr. Zink in North Dakota notes that many roads, including interstates, were designed for the lower weights of yesteryear, and he says today's big trucks do swift damage. Other experts say a road with a life-expectancy of 20 years may see that time frame cut by five years because of heavier weights.

In North Dakota, where truck weights can run as high as 105,000 pounds (some states may exceed federal limits under a ``grandfather'' provision), engineers are finding that asphalt can't do the job, so they are being forced to go to concrete roadways, Zink says.

There are also other factors. Mountain states report that steel-studded snow tires on cars are adding to the rutting problem being caused by bigger trucks.

David S. Gindell, director of the Office of Highway Operations at the Federal Highway Administration, says higher truck-tire pressures also hurt. Mr. Gindell says new tires can be inflated to as much as 125 pounds per square inch. This boosts gas mileage, but it also reduces the ``footprint'' of the tire, putting more weight on a smaller area.

Congress anticipated such problems. The economic benefits of tandem trucks, greater weights, and other changes were worth the extra cost, Congress decided.

John Reith, director of highway policy for the American Trucking Association, says: ``All of the studies that have been made of cost/benefit ratios have shown a great deal more benefit than cost in the higher [truck] weights.''

In some cases, new trucks are able to carry as much as 25 percent more volume than under the old weight rules.

Mr. Reith also notes that some tire makers dispute charges that higher tire pressures cause more damage. Many new tires with higher pressures are radials, and these actually have a larger footprint, Reith observes.

While truckers may disagree with highway builders on the weight issue, there is greater agreement on the equally controversial subject of the higher 65 mph speed limit.

This week, New Mexico reported that the number of people killed on its highways has more than doubled since the higher speed limits went into effect on April 2, compared to the same period a year ago.

This was no surprise to some experts. About two months ago, a survey of New Mexico motorists found that nearly half the drivers were exceeding the new, higher limit.

The trucking association's Reith says most truckers still like the old 55 mph limit.

``55 is good business,'' he says. ``It cuts wear and tear on equipment and lowers fuel consumption. The safety factor was also substantial, with a reduction in accidents. The additional driver cost was minuscule in relation to the benefits.''