The trucks that do the most damage to Maine roads are not the behemoth tractor trailers, but the smaller open-sided logging trucks.
The stress on a road is determined by the axle load, according to experts. For example, an eighteen-wheeler carrying a legal load of 100,000 pounds distributes 16,667 pounds to each axle. By contrast, a four-axle truck carrying a legal load of 75,900 pounds distributes 18,975 pounds to each axle.
“That’s the most severe loading,” Chip Getchell, assistant to the chief engineer at Maine Department of Transportation, says of the four-axle limit. “It’s such a concentrated load. It’s hard on bridges and it’s hard on pavement.”
Maine’s relatively generous truck weight limits is a factor in the state’s low ranking in pavement conditions (38th in the country), according to David T. Hartgen, who conducts an annual nationwide survey of road conditions. Maine allows 100,000-pound trucks on state roads, while many states have lower weight limits, he said.
Heavier trucks cause disproportionately more damage, said Jerry Donaldson, the research director for Advocates for Highway and Auto Safety, a research and lobbying group opposing a trend toward more relaxed truck weight limits.
“Incremental increases in vehicle weight cause exponential increases in road damage,” said Donaldson.
Sen. Dennis Damon, co-chairman of the Maine Legislature’s Transportation Committee, says the 100,000 limit is “becoming the standard” (nationwide), and if Maine were to buck the trend and adopt a lower limit it would be viewed as “yet another business-unfriendly regulation.” “I can hear all kinds of arguments,” he said.