BOSTON -- Some 500 bridges in Massachusetts are deemed structurally deficient, yet Team 5 Investigates caught some of the potentially most dangerous trucks - fuel tankers -- routinely ignoring legal weight limits.

Take the Alford Street Bridge, which connects Everett and Charlestown, and is within a stone's throw of fuel depots where tankers fill up before making deliveries. NewsCenter 5's Janet Wu reported Thursday that nine weight limit signs are posted, yet police stop an average of a dozen violators daily.

Wu: How dangerous is it for the trucks to go over there?

Sgt. Joseph McNiff, Boston Police Department: Extremely.

Wu: They do it all the time?

McNiff: Yes, that's why we do the enforcement.

The potential for disaster is real. Last August in Minneapolis, 13 people were killed and more than 100 injured when the main spans of a bridge over the Mississippi River collapsed. In Connecticut, a 100-foot section of a bridge fell into the Mianus River when steel pins holding horizontal beams failed, killing three.

"It wasn't until a series of loaded tractor-trailers went over it that the bridge failed," said Merrimack College engineering professor David Westerling. "We wouldn't want that to happen here."

Empty fuel trucks headed for the Everett filling terminal are under the weight limit. But Team 5 Investigates caught truckers boldly going over the bridge with full loads, often double the legal weight limit.

The violations are even more surprising given the fact that after December's massive tanker explosion just a mile away, drivers had been warned to follow the letter of the law. We confronted one of those drivers who didn't, late one night.

Wu: Excuse me sir, did you go over the Alford Street bridge with a load that exceeded the limit tonight?

Driver: No.

Wu: We saw you. We got you on video going over the Alford Street bridge with a full load. It's illegal to drive over the Alford Street bridge, do you know that?

Driver: Yes, I do. I always go around, I said.

Wu: But you didn't, we followed you.

Driver: I don't know what to tell you.

What's more, Team 5 Investigates has confirmed that the pay structure at at least one company gives drivers financial incentive to take the shortcut over the Alford Street bridge.

Three J.P. Noonan drivers told Team 5 Investigates they are paid a flat rate for each delivery, compared to most other companies which pay their drivers by the hour, no matter how long it takes.

A J.P. Noonan executive insisted its drivers are paid for their time, but later admitted they're paid according to how long the company believes it should take drivers to make a delivery. He added that Noonan has instructed its drivers not to use the bridge when carrying a full load.

Dennis Royer, Boston Public Works commissioner, said drivers who ignore the legal weight limits are endangering the public every time they drive over the bridge.

"That vehicle is carrying a flammable, hazardous material. It's the same as Russian roulette. You can spin the revolver so many times. As long as it clicks on empty, you're fine. What happens if you hit the bullet?" Royer said. "That's what happened here and that's the game they're playing with us."

The bridge has been slated for renovations since 2004 but funding and design problems have pushed repairs past 2009. Meanwhile, every day overweight trucks continue to pound the pavement and add stress to the beams.

"You don't know what time or how many people will be there when the accident occurs," said Royer.