AUGUSTA – Sprawled at the flanks of the Maine Turnpike near the state’s southern gateway, a pair of weigh stations are spit-shined, well-maintained, ready for action – and as nearly any commuter can attest, almost always closed.

When they do open, word gets around fast. Some truckers pull to roadsides in neighboring New Hampshire to wait it out, state police observe.

“I’ve heard troopers say [truckers] know I’m there before I know I’m there,” said Herb Thomson, a spokesman for the Department of Transportation.

But Mainers needn’t worry that the state is asleep at the scales while overloaded trucks freely chew up more than 22,000 miles of public roads and highways in the state.

Invisible eyes are watching.

Under the asphalt where no one can see, the Department of Transportation has a dozen devices that collect weight data as the big trucks whiz by.

Two weight-in-motion or WIM devices are located along the Maine Turnpike, two on regular interstates and the rest on state highways, working 24-7 collecting weight data.

They don’t paint a pretty picture of what the trucks are doing. Figures considered conservative by the DOT indicate that statewide, about 16 percent of the trucks – or one out of six – were overloaded in 2000.

The latest figures, collected by the underground weight detectors in 2002, point to some particular trouble areas.

On tractor-trailers, the two-axle or “tandem” combinations on the rear of the tractors exceeded interstate weight limits nearly 50 percent of the time along I-295 in southern Maine, and 42 percent of the time along I-95 in Penobscot County.

The percentage of violations was worse at a WIM site on a state road in a logging area of Aroostook County. On tractor-trailers, the tractor’s tandem axles and the trailer’s triaxles at the rear were overweight 59 percent of the time.

On four-axle single-unit trucks, the kind commonly used by pulp haulers, the rear triaxle was overweight 47 percent of the time at the WIM site on I-295 and nearly 63 percent of the time on the Aroostook logging road.

The WIM devices picked up smaller percentages of overloads at other sites, which include Oxford, Kennebec, Somerset, York, Washington and Androscoggin counties as well as another one in Aroostook and along the turnpike in York and Cumberland counties.

Transportation officials are reluctant to reveal the exact locations of the WIM sensors for security reasons and out of concern truckers will avoid them. They did recently publicize the presence of a WIM device at the Waldo-Hancock Bridge along Route 1 to bolster weight enforcement on the aging span near Bucksport.

Statewide, overloaded trucks translate into at least $8.4 million in damage per year – the equivalent of about a penny on Maine’s gasoline tax – to the state’s highways alone, the DOT told the Legislature in 2001 when it passed a law increasing fines for overweight trucks for the first time since the mid-1970s.

That doesn’t include the added cost of damage to more than 860 bridges that aren’t designed for the heavy loads newer trucks can haul.

Put another way, one truck per day overloaded by 45 percent can shave one to two years off some highways, the DOT says.

The WIM sensors, like those in a number of other states and provinces, include metal loops and plates embedded in the highways that record axle configuration – a major factor in overloading – and weight as the vehicle moves along at highway speed.

Used since the 1980s in Maine, the devices are used solely for data collection and planning, not for enforcement action.

The enforcement is handled by the state police, part of the Public Safety Department, which has a 40-person unit using portable scales that are set up almost daily in different locations, said the commercial vehicle enforcement unit’s Lt. Tom Kelly.

Figures from last year were incomplete, but in 2004 the portable scales weighed more than 10,000 commercial trucks. The number of actual violations for 2003 show 1,901 in Maine, according to state figures reported to the Federal Highway Administration.

The total includes axle, gross and bridge weight violations, as well as the number of trucks that were required to unload or shift their loads to comply with weight laws.

Movable scales sometimes are used to confirm violations recorded by the WIM sites, such as along the northbound lane on I-95 in York, where a WIM device on the ramp to the weigh station screens trucks. Those found to be overweight are put on portable scales.

Across I-95 along the southbound lane, the weigh station has built-in scales used by state police.

Kelly acknowledged that word quickly spreads when the stationary sites open and that some truckers lie in wait or detour to avoid enforcement. In southern Maine, some switch to coastal U.S. Route 1 to end-run the scales.

“There are times we put people on Route 1 just to deal with that,” said Kelly. As for truckers with overloaded freights who pull off the road, “you can only wait us out for so long,” he said.

Maine has limits for axle weights as well as gross truck weights, and limits vary according to number of axles. In Maine, federal limits are more stringent than the state’s, a concession to natural resource-based industries such as forest products, sand and gravel and potato-growing industries that are important to the state’s economy.

Under federal limits, which apply on the interstates other than the turnpike, the outside limit is 80,000 gross weight, while on state highways the maximum allowed is 100,000 pounds. Axle weight limits are also higher on state highways.

Kelly said he has seen some trucks exceed the gross weight limit by as much as 40,000 pounds and several in excess of 20,000 pounds.