The Mississippi Transportation Commission (MTC) is saying no to congressional legislation that would modify vehicle weight limitations for the Interstate Highway system. The legislation would allow the possibility of “Twin-33’s” on those systems.
The MTC wrote a letter to the Mississippi Congressional Delegation saying that the proposed length and weight will violate current bridge formulas and decrease safety and increase repair costs.
The current bridge formula, created in 1975 by the Federal Highway Administration (FHWA) protects bridges from damage by heavy trucks. The six-axle trucks were originally proposed in 2015 and brought back before lawmakers this year.
The USDOT claimed that the report released in 2016, Final Truck Size and Weight Limit Study, showed that there was not enough data to prove that larger trucks would be safer.
The American Society of Civil Engineers said that one in nine bridges is structurally deficient, and in Mississippi that number is one in eight. Overweight trucks would cause damage to the already deteriorating roads in bridges here.
“The limited data available actually shows that heavier trucks have higher crash rates and that longer trucks take 22 feet longer to stop, causing considerable bridge damage,” said the MTC in its letter to Congress. “Our maintenance efforts are already seriously underfunded. This type of legislation would further contribute to the destruction of bridges and to the cost of repairs and rehabilitation on states, and ultimately the public.”
An 18,000-pound truck axle does over 3,000 times more damage to pavement than a typical passenger vehicle axle. increasing that weight by only 10 percent, increases the damage by 33 percent.