PORTLAND — Officially, the national weight limit for freight trucks on interstate highways is 40 tons. In reality, trucks are getting heavier in more states – legally – and advocates for highway safety and the trucking industry are sharply at odds about it.

Trucks heavier than 80,000 pounds are allowed to operate on federal highways in at least 20 states. Congress added Maine and Vermont to the list last week, granting exceptions to allow trucks up to 100,000 pounds on interstates there for the next 20 years. The change went into effect Friday when President Barack Obama signed it.

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A heavy truck travels north on Route 1, alongside Interstate 295, in Yarmouth recently. Congress' vote to increase truck weight limits on federal highways in Maine and Vermont highlights the arguments for and against allowing heavier trucks on the nation's interstates. AP

Critics say that heavier trucks make highways less safe because they’re harder to control and stop, and that they leave taxpayers on the hook for damage to roads and bridges. Furthermore, they claim, the latest increases will spur the trucking industry to seek higher limits in other states.

“The trucking industry is energized by what’s happened in Vermont and Maine,” said Jackie Gillan, president of the Washington-based Advocates for Highway and Auto Safety organization. “The American public is going to pay with their lives and their wallets.”

But supporters of higher weight limits argue that allowing heavier trucks will actually make highways safer because fewer trucks will be able to move the same amount of goods. With fewer big rigs rumbling around, it’ll cut pollution and reduce the cost of doing business, they say. And concerns about road and bridge damage are overblown, they claim.

“Whatever arguments the opposition puts out there, if you look at the research, their arguments don’t hold water,” said Darrin Roth, director of highway operations at the American Trucking Associations.

Before the new law went into effect raising the weight limit in Maine, Douglas Haskell, a truck driver from Palermo, had to drive loads of cement powder along two-lane state highways — even with Interstate 95 nearby — for delivery to northern Maine, New Brunswick and Quebec.

He drove through school zones, over railroad crossings and in small towns, while dealing with cars in break-down lanes, moose and pedestrians. Allowing larger trucks cuts emissions, saves on fuel and cuts down on driver stress, he said.

“If we all cut back to 80,000 pounds, we’d probably have twice as many trucks on the road, so what are you accomplishing there?” said Haskell, who’s been a trucker for 38 years. “You’re going to have twice as many trucks out there creating havoc with the public.”

Thursday’s congressional vote adds to a jumble of inconsistent highway weight laws around the country that’s been around since the interstate network was created in 1956. Back then, Congress set a limit of 73,280 pounds on federal highways but at the same time authorized states to allow heavier trucks if they already did so on state highways.

Congress in 1974 gave states the option of raising the interstate limits to 80,000 pounds, and in 1982 required all states to adhere to that limit. In 1991, it prohibited states that didn’t already allow double and triple trailers from doing so.

Congress has generally allowed states to grandfather existing laws. Several states allow some trucks weighing more than 100,000 pounds or make exceptions for specific products, such as sugarcane, milk, logs or coal, according to the Federal Highway Administration.

Over the years, the trucking industry and other groups have argued for higher weight limits. The railroad industry, safety groups and others have argued against them. Both sides cite report after report they say support their positions.

A bill submitted by U.S. Rep. Jim McGovern, D-Mass., called the Safe Highway and Infrastructure Preservation Act, would freeze the 80,000-pound limit on federal highways.

Bigger, heavier trucks are more likely to get into accidents and damage highways and bridges, said Jennifer Walters, legislative assistant to McGovern. A recent study in Illinois concluded that raising the truck weight limit from 80,000 to 97,000 pounds on federal highways would cause an additional $162 million in damages annually to federal highways there, she said.

Besides adding to the nation’s infrastructure woes, giving weight exemptions to Maine and Vermont “starts us down a slippery slope of allowing other states to ask for a special weight limit exemption,” McGovern said during congressional debate last week.

A competing bill submitted by Rep. Michael Michaud, called the Safe and Efficient Transportation Act, would allow six-axle trucks weighing up to 97,000 pounds on federal highways, with states having the option of increasing the weight limits.

The Maine Democrat said he was impressed by an Alabama business owner’s testimony in Congress a few years ago that allowing heavier trucks on the roads would save him $73,000 a week in fuel costs, reduce carbon monoxide emissions by 130,000 pounds a week and reduce the number of his trucks on the road from 600 to 450.

In states such as Maine and Vermont, he said, higher weight limits get the biggest trucks off rural two-lane highways and onto the interstates, where they pose less danger.

“When you look at economic impact, environmental impact, safety impact, it’s positive in all three areas,” Michaud said.

Gillan, of the Advocates for Highway and Auto Safety, said the answer isn’t to raise interstate weight limits, but rather to force states to lower limits on their state roads to 80,000 pounds, in accordance with the federal standards.

“Guess what?” she said. “These trucks shouldn’t be on any of these roads.”

The American Trucking Associations favors raising the national standard for truck weights to 97,000 pounds, with states having the final say on whether those limits should apply within their borders.

A 97,000-pound limit won’t result in additional road damage because the weight will be spread across six axles, not five, Roth said. He conceded that there is a “potential concern” for bridge fatigue from heavier trucks, but said most bridges on the interstate are designed to handle weights in excess of 80,000 pounds.

A Department of Transportation study completed in 2000 examined what would happen if the limits in Canada, which allows heavier trucks, were applied to the U.S. It found the limits would reduce shippers’ costs by $13.3 billion annually and reduce truck vehicle miles by 13.7 billion.

Some suggest that the railroad industry opposes heavier trucks because it would create more competition and force railroads to cut rates to remain competitive, a claim that makes Patty Reilly, spokeswoman for the Association of American Railroads, bristle.

Trucks, through diesel fuel taxes, pay for only 80 percent of the damage they do to highways, she said. That leaves taxpayers to foot the bill for $2 billion in road repairs each year, she said.

“Taxpayers don’t pay for the railroads, but taxpayers help pay for the damage inflicted by heavier trucks,” she said. “This isn’t an issue of competition. This is an issue of is it fair that taxpayers are subsidizing one form of transportation over another.”

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