Renegade truckers who pack illegally heavy loads and haulers who don't understand Minnesota's complex truck-weight laws inflict an estimated $30 million a year in damage to state roads, bridges and railroad crossings.

Yet state officials who oversee commercial vehicles are ill-equipped to deal with the problem, consultants hired by the state have concluded.

Tighter State Patrol budgets, along with legislation allowing heavier loads for some industries, have made it harder than ever to enforce truck size and weight laws. Despite steadily increasing truck traffic, State Patrol overweight citations have dropped 21 percent since 2002.

Making matters worse, truck-weight enforcement on most county and city roads is the responsibility of county sheriffs and local police -- and few have the training, staff or equipment for the job.

It's unknown whether excessive truck loads played a role in the Aug. 1 collapse of the Interstate 35W bridge. But the National Transportation Safety Board is analyzing factors that include structural fatigue.

Officials at the Minnesota Department of Transportation and the State Patrol say they have no idea whether overweight trucks had been regularly crossing the I-35W bridge.

Tickets for overweight trucks don't offer clues, either. The Star Tribune analyzed overweight citations issued by the State Patrol since Jan. 1, 1997, and found that just two tickets had been issued on I-35W in Hennepin County: one in 1997 and one in 2000.

"With the traffic volume on that corridor, it makes it very difficult for us to even conduct a traffic stop for a truck," said Capt. Ken Urquhart, commander of the State Patrol's Commercial Vehicle Enforcement section.

To nab more overweight trucks, MnDOT and the State Patrol are evaluating high-tech enforcement tools, including "weigh-in-motion" scales embedded in pavement and "virtual weigh stations." But the systems are expensive to buy and maintain.

Cecil Selness, MnDOT's director of freight and commercial-vehicle operations, said the agency has used embedded scales in roadways to conduct research on pavement design. But he said no such work had been conducted at the I-35W bridge, which MnDOT inspectors had rated "structurally deficient" since 1990.

Study highlighted problems

A study of overweight trucks conducted for MnDOT and the State Patrol by URS Corp., a San Francisco engineering firm that also studied the I-35W bridge before its collapse, recommended comprehensive changes to the state's truck weight enforcement program.

"Unfortunately, while the demand for compliance has been increasing, enforcement resources ... have steadily diminished," says the report, which was issued two years ago and cost $75,000. "This is in part due to state government budget cuts and increased operating expenses," it said.

URS recommended a four-phase strategic plan to increase truck-weight compliance by 10 percent, which it estimates would prevent about $3 million a year in damage.

Most truckers operate within the law. But even a small number of overweight trucks -- in the neighborhood of 1 to 3 percent -- can reduce pavement life by 25 percent or more, the URS report says. It did not evaluate the damage done to bridge structures because of the difficulty of calculating the effects that overweight trucks place on structural supports.

The study found that the state's fixed inspection stations "rarely find violators" and recommended installing more weigh-in-motion sensors in pavement. It suggested the establishment of a network of "virtual weigh stations" that would help the State Patrol target scofflaws on heavily traveled routes.

The state operates six permanent truck scales, the busiest of which is the St. Croix scale on westbound I-94 in Washington County. But the URS report says it has become increasingly difficult for the State Patrol to maintain staffing at the scales.

The St. Croix scale opened in 1987 with 25 people operating three shifts a day, it says. "They now operate only one shift each day with a staff of 4 to 5 people."