North Carolina's weak laws regulating overweight trucks and poor enforcement by the state Highway Patrol show up every year in a place you might not have considered: Your taxes.

Every day, at least 100,000 medium-sized and big trucks are on the move in North Carolina. One legal truck, weighing 80,000 pounds, does at least as much damage to roads as 5,000 cars, experts say. And damage from heavier trucks -- running illegally or approved by special state laws -- goes up dramatically.

No one can say precisely how much heavier trucks cost taxpayers in additional repairs, but Len A. Sanderson, the state highway administrator, says there's a direct connection.

"More weight, more tearing up, the more maintenance money you need," he said.

How many trucks might be overweight would only be a guess were it not for an obscure unit in the state Department of Transportation that has been gathering data on truck weight for a federal pavement study.

The data include records of about 440,000 tractor-trailers weighed in 2003 by equipment buried in the pavement at 16 locations in 12 counties. According to an analysis by The News & Observer, one truck in 12 weighed more than 80,000 pounds, the interstate maximum.

More significant: In the wee hours of the morning, trucks are three times as likely to be overweight as trucks moving during the day, when weigh stations are more likely to be open and when weight enforcement officers are more likely to be on patrol.

DOT told the Federal Highway Administration that it would share that data with officers responsible for catching overweight trucks, but it hasn't. Kent L. Taylor, state traffic survey engineer, said the data could generate better decisions on what time of day to have enforcement officers working.

"We just haven't had the staffing to do that," he said about sharing the data.

The state spends about $615 million a year to maintain its highway system, Sanderson said. It needs to be spending $1 billion, he said, and part of that can be blamed on overweight trucks.

The money for maintenance and other highway needs comes primarily from the state and federal taxes on fuels. The total tax on a gallon of diesel, which trucks use, is 51.25 cents. The tax on gasoline, used by most cars, vans, pickups and SUVs, is 45.25 cents per gallon. Still, a federal study says big trucks don't pay their fair share because of the damage they cause.

Legislators have not raised overweight truck fines in 24 years. Instead, for some of the most frequent violators, they have upped the legal weight limits and cut the penalties in half. In effect, after adjusting for inflation, many overweight trucks are fined a fourth as much as they were in 1981, the last time penalties were raised.

Heavy load, high cost

Judith Corley-Lay, the state's top pavement management engineer, says she has been asked often by legislators how much another increase in weight limits would cost in damage.

"Every single year I get called in to answer some various nuance of the question," she said. "If we increase the load limit to X, what is the dollar cost of that increase? And it's a very frustrating question because it's very complicated technically."

But Corley-Lay has calculated what would happen -- and how much it would cost -- in a hypothetical situation. She said if truck weights were increased 10 percent on interstate highways, pavement designed to have a 20-year life would wear out in seven. And maintenance would increase by $129 million a year.

But interstates account for only 1,019 miles of the state's 78,615-mile highway system. So the cost of a 10 percent increase on the state's primary and secondary roads would substantially increase Corley-Lay's damage estimate.

Overweight trucks tear up a road much faster than legally loaded trucks because as weight goes up, stress on the road goes up faster. An increase in truck weight of 20 percent, for example, would result in a 73 percent increase in stress on the road.

"The heavy loads really do increase the increment of damage per truck," Corley-Lay said. "There's no question about it."

The damage to a major highway is usually gradual and might not show up for years. A lightly built subdivision road, however, can go to pieces in a few weeks.

"It is not that uncommon for the construction traffic, which is almost all trucks, to [ruin] the road before the first house is ever completed," she said.

Glenn Mersinger has lived on Green Level Church Road since 1984, back when it was out in the country and there was no traffic worth mentioning. Now the road in front of his house, which runs about 6 miles from U.S. 64 near Apex to the Chatham County line, is so heavily traveled he has a hard time getting out of his driveway in the mornings and evenings.

When he does, it's a rough ride. Green Level Church Road's patches have patches. He blames that on dump trucks, sometimes three and four at a time, to and from construction sites.

"Dump trucks will tear a road up in a little bit," Mersinger said.

Secondary roads suffer

Legislators can't increase weight on the interstates. Congress controls weights on those highways, and, so far, it has held the line at 80,000 pounds. Lawmakers here, however, have voted repeatedly to raise weight limits on other roads above the 80,000 pounds allowed on interstates; the top weight allowed is 90,000 pounds for farm trucks.

Lyndo Tippett, state secretary of transportation, didn't know what the weight limits are on secondary roads. He was incredulous last month when he was told by The News & Observer that legislators had passed numerous bills allowing trucks on secondary roads that are so heavy they aren't allowed on interstates.

"Think about it," he argued. "Secondary roads carrying as much weight as an interstate? Secondary roads just have a little coating of asphalt.

"I can't comprehend that sort of legislation being advocated considering the billions of dollars we've got invested in the highway infrastructure. It's been my focus for the last four years to maintain, spend money on maintenance, trying to get the roads back in condition."

The weight laws have passed since Tippett has been a member of the Board of Transportation or transportation secretary.

Tippett didn't know the law, but he was right about the weakness of secondary roads.

A typical two-lane secondary road is likely to have a thin layer of asphalt -- maybe 2.5 inches -- spread over 6 inches of stone, at a cost of $54 per linear foot of highway. A four-lane interstate highway might have 15.5 inches of asphalt over 10 inches of stone over 6 to 7 inches of soil mixed with lime or cement and compacted. The cost would be about $470 per foot.

"If the [secondary] road is not built to the standard to take care of truck traffic and you get a big subdivision in there, several hundred homes, that road's gonna crumble like an alligator's hide," said Dan DeVane, one of Tippett's deputies.

Truck taxes fall short

Associations representing business interests have successfully lobbied the legislature to allow fully loaded trucks to use roads posted with lower weight limits by DOT engineers.

The maximum weight normally allowed on a posted secondary road is 13,000 pounds per axle. The legislature, however, has passed laws to allow trucks hauling some commodities, such as wood chips, to use posted roads with axle weights of 20,000 pounds.

There are 2,305 miles of posted roads in North Carolina, nearly enough to reach from Raleigh to Los Angeles; Wake County has 169 miles, the most in the state.

To prevent "undue" damage, DOT has the authority to stop the trucks given special permission by the legislature from driving on posted roads. But Sanderson, the highway administrator, said he didn't think that had ever been done.

Spokesmen for the farm and forest industry lobbies say their industries shouldn't have to pay for the damage they do because they already pay so much in taxes. The average for all tractor-trailers in North Carolina is $6,107 a year, according to the American Transportation Research Institute.

Trucks are taxed more heavily than cars, experts say, because they do most of the damage.

"Cars are almost inconsequential," Corley-Lay said.

Here's how trucks pay more:

* They pay the slightly higher tax on diesel fuel. And since big trucks only get about 5.7 miles to the gallon, they pay about four times as much tax per mile.

* Truck owners must buy tags for all the states they work in, which could cost up to $1,500 a year; most car owners pay $20 for a North Carolina tag, and they can go anywhere.

* If a truck's registered weight is 55,000 pounds or more, the owner must pay an annual federal "heavy vehicle" use tax of up to $550. There is no similar tax on cars.

But a federal study says those heavier taxes aren't enough for fully loaded tractor-trailers.

A study in 2000 by the U.S. Department of Transportation indicates that car, van and pickup owners are paying more than their share of highway construction and maintenance costs.

Many trucks are, too, but that changes as weight increases.

Fully loaded trucks in the 75,000- to 80,000-pound range pay 91 percent of their fair share of highway costs, according to the study. Trucks weighing 80,000 to 100,000 pounds pay 57 percent; trucks weighing more than 100,000 pounds pay 50 percent.

Besides doing far more damage, trucks have one key advantage in taxes: In North Carolina, the 3 percent one-time highway use tax paid when the vehicle is purchased is limited to $1,000 for trucks. There is no ceiling for cars.

Fines for truckers are another source of revenue, but they've been getting smaller. Consider the penalties levied in March when driver Troy Lee Williams, hauling wood chips, was stopped by enforcement officer Ricky K. Phillips.

Williams' truck weighed 85,200 pounds -- overweight by 5,200. The drive axles had too much weight on them, too. The legislature has given wood-chip trucks a 4,000-pound tolerance on gross weight, but when a truck exceeds that tolerance, the maximum weight reverts to 80,000 pounds.

The penalty for exceeding 80,000 pounds is 2 cents a pound for the first 2,000 pounds, 4 cents for the next 3,000 pounds and 10 cents a pound for everything over 5,000 pounds, or a total of $180 for Williams' truck that day. That's then cut in half because legislators have voted to give chip trucks a 50 percent break on fines.

For being 1,950 pounds overweight on each of two drive axles, the fine was 4 cents a pound for the first 1,000 pounds and 6 cents for the next 950, or $194, also divided in half. Total fine: $187.

(News researcher Brooke Cain and database editor David Raynor contributed to this report.)

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