Overweight vehicles are shortening the life span of Arizona's roads and bridges and leaving behind millions of dollars in damage each year, according to state officials.

Illegally overweight vehicles cause an estimated $12 million to $53 million a year, according to a study last year by consultant Sandy H. Straus and the Arizona Department of Public Safety.

The study found that amount is not covered by the fines truckers pay when they get caught nor by fees truckers pay for permits to exceed weight limits.

``Looking at a number of different measures, it's pretty obvious to me that the heavier vehicles are not paying sufficient fees and taxes to cover the wear and tear they impose on the pavement,'' said John Semmens, a project manager with ADOT's Transportation Research Center.

Some experts warned that permits allowing trucks to exceed weight limits can weaken steel and concrete, something that investigators say may have contributed to the Minneapolis bridge collapse that killed 13 people on Aug. 1.

Gov. Janet Napolitano ordered a review of all state bridges in response to the Minneapolis collapse. After officials inspected 170 of them and reviewed records on more than 630 others, Arizona Department of Transportation Director Victor Mendez pronounced them all safe and accelerated repairs on three bridges.

But engineers liken the effect of heavy trucks on a bridge to bending a paper clip: It can bend again and again without breaking, but eventually it will snap.

The weight limit for nearly all interstate highways is 40 tons. But permits frequently allow vehicles to exceed that amount by 2 tons in Texas and sometimes as much as 85 tons in Nevada. Some states grant one-time permits that allow trucks to be considerably heavier.

The state is selling more overweight permits per heavy-truck mile traveled and issuing more citations than most neighboring states, according to the ADOT study.

Arizona Trucking Association officials declined to comment Monday.

Darrin Roth, director of highway operations at the American Trucking Association, said it's not fair to put all the blame on trucks because permit loads are a tiny proportion of total traffic.