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Thursday, September 20, 2007
Nation's Road Infrastructure Under Great Stress
Our nation's roads and bridges are swollen with over a half-million overweight trucks. Some experts say this increasingly normal practice is putting dangerous wear and tear on an already groaning transportation network.
In interviews with The Associated Press, officials warn that issuing state permits that allow trucks to exceed the usual weight limits can weaken steel and concrete. Investigators say this practice may have contributed to the Minneapolis bridge collapse that killed 13 people.
Don Lee, executive director of the Texas Conference of Urban Counties, said, "We talk about this all the time and the fear that we have is that we're going to have the same sort of disaster here that happened in Minnesota."
Milwaukee's Hoan Bridge collapsed in 2000 when steel girders cracked. Several factors, including a considerable number of heavy trucks over the normal weight limit regularly traveling over the bridge, were blamed for the collapse.
Nearly all interstate highways have a weight limit of 40 tons. A government study revealed that one 40-ton truck does as much damage to the road as 9,600 cars. Yet permits frequently allow vehicles to exceed that amount by two tons in Texas and as much as 85 tons in Nevada. Some states award one-time permits that allow trucks to be significantly heavier.
Transportation officials around the country dismiss such fears and say roads and bridges are safe, though some are concerned that insufficient funds are being spent to repair the damage done by overweight trucks.
Many state officials said they have no choice but to issue overweight-load permits; they are simply carrying out the laws as passed by the legislature. Critics say they the laws are often written to benefit powerful local industries, such as logging in the West, or oil and gas in Texas.
In the overwhelming majority of cases, a single truck can safely pass over a sound bridge, even if the rig exceeds the posted weight limit. But the collective effect of stress on the steel and concrete can eventually prove fatal.
Engineers compare the effect of heavy trucks on a bridge to bending a paper clip: It can bend without breaking again and again, but eventually it will snap.
For overweight-load permits, many states charge fees ranging from $12 to $1,000, depending on the weight of the load. In theory, those fees offset the destruction done to the highways.
For example, Texas granted nearly 39,000 such permits in the past year, generating $7.5 million, the bulk of which was divided among the state's 254 counties for road maintenance.
Chris Lippincott, a spokesman for the Texas Department of Transportation, said, "That in no way even comes close to covering the wear and tear on our roads and bridges in this state."
It is not fair to put all the blame on trucks because permit loads are a tiny proportion of total traffic, said Darrin Roth, director of highway operations at the American Trucking Association.
According to an AP review of figures in all 50 states, more than 500,000 overweight trucks were allowed to cross the nation's bridges and highways at will in the past year. Those permits did not expire for an entire year. Although 10 states do not issue yearlong permits, all states issue shorter-term permits good for a few days, weeks or months, adding up to more than 1.8 million permits not included in the AP's count.
Many states, including Texas, have reported a small increase in the number of overweight-load permits issued in recent years — a rise that Roth said can be credited to a 2.5 percent to 3 percent annual increase in truck traffic because of the growing economy.
Eric Lockwood routinely carries 42 tons of hot oil all over Texas and has a state-issued overweight-load permit. He said he doesn't worry much about bridges and weight limits.
"From what I understand, the way those bridges are engineered and built — even the ones that do have a weight limit on them — you can grossly exceed that weight limit without having a problem," Lockwood said. "That's what I've heard. I don't know what the truth is."
Although the permit does not allow him to travel on interstate highways, he does so anyway about half of the time. He said that when he gets ticketed, his company pays the fine.
Recently, he crossed an old wooden bridge with no guardrails to deliver fertilizer to an East Texas rancher. "I've never really given it a second thought," he said.
California is more careful with its overweight permits. With about 23,000 single-trip permits issued annually, truckers must request permission to travel on a specified route for each trip.
Extensive reviews are performed by California transportation officials to ensure the load can safely travel on the requested highways without damaging pavement and bridges. Often, truckers are obliged to reduce their loads.
But in Colorado, drivers operate on the honor system, and officials say they have no way of knowing if drivers are taking bridges appropriate for their loads. Almost 21,000 permits are issued annually in Colorado, and truckers are given a map with their overweight permits showing how much weight bridges around the state can handle.
"There's definitely room for improvement," said Colorado Transportation Department spokeswoman Stacey Stegman. "But by no means are we alarmed."
A recent federal finding discovered that 18 percent of U.S. bridges either do not have weight limits posted or incorrectly calculate the weight limits that are posted. Also, a federal study last year classified 26 percent of U.S. bridges as either structurally deficient or functionally outdated.
In the year before the Minneapolis disaster, the cause of which is still under investigation, the state Transportation Department granted 48 overweight load permits, including construction cranes and supplies weighing up to 72 1/2 tons.
The bridge was one of over 73,000 U.S. bridges that had been categorized as structurally deficient last year.
Trucks are generally not allowed to exceed the 40-ton weight limit on interstate highways. However, some stretches of interstate have higher weight limits due to the fact that they were grandfathered in when the federal interstate system was created during the Eisenhower administration.
Certain vehicles are allowed to operate without obtaining overweight-load permits, and the numbers compiled by the AP do not include these vehicles. For example, in Texas, vehicles transporting ready-mix concrete, milk, solid waste, recyclable materials, seed cotton or chili pepper seedlings are not required to have an overweight permit on state roads, even if they are over the limit.
Other states allow similar exemptions.
State policies vary a great deal, with some much more lenient than others. Many states refuse to issue permits for loads that can be easily split up and carried at safer weights.
"It's one of the most befuddling policies we deal with, that we spend millions of dollars to build roads ... and the state comes along and for a pittance gives out a permit to allow trucks to destroy those roads in a matter of months or years," said Lee, the Texas official.
The National Safety Commission recommends The Driver Education Handbook for Parents as a valuable teaching tool for parents who are concerned with their teen's driving safety and understand the value of quality instruction.