In 1956 Congress legislated maximum axle weight, gross vehicle weight, and width limits for trucks operating on Interstate highways.
Congress adopted the weight limits recommended in 1946 by the American Association of State Highway Officials (AASHO), now the American Association of State Highway and Transportation Officials (AASHTO): 18,000 pounds on a single axle, 32,000 pounds on a tandem axle, and 73,280 pounds gross weight.
In 1982 Congress required that all States allow on their Interstate highways loads of 20,000 pounds on single axles, 34,000 pounds on tandem axles, 80,000 pounds total for a vehicle, and enforce the Federal Bridge Formula. The width limits were increased to 102 inches. States were required to allow 48-foot semitrailers and double combinations of two 28-foot trailers.
The vehicle weight limits – 18,000 pounds on a single axle, 32,000 pounds on a tandem axle, and 73,280 pounds gross weight – enacted in 1956 were to protect Interstate System pavements and bridges from damage or premature wear caused by excessively heavy trucks.
What I am trying to show here with this is, the vehicle weight limits enacted in 1956 were done so to protect roads and bridges. In 1982 congress required states to allow heavier truck gross amounts up to 80,000 pounds on the same roads and bridges. Now some states are wanting to raise these limits from 80,000 pounds up to 97,000 pounds. The problem is that they want the increase on some of these very same roads and bridges from 1956 or roads and bridges that are 54 years old.
If heavier vehicles were allowed to operate there would need to be a substantial number of bridge improvements. Heavier six-axle tractor-semitrailers, such as the 97,000-pound vehicle that would, generally exceed bridge formula limits and would cause stresses exceeding bridge design stresses. In 1999 there was a total of 585,542 bridges in the US of which 88,150 were considered structurally deficient by a recent report there are now 603,259 bridges in the US, of which 71,177 are considered structurally deficient. This does not include any roads this is just bridges only.
It’s evident that roads and bridges were not built to last forever as we see road and bridge construction every year. I have written articles before telling how I used to drive a tractor trailer and the type of trailer I pulled was a dump trailer. I hauled out of coal mines and rock and sand quarries in Ohio and Kentucky. In 1996 most quarries did not have any limits on the weight you could gross when you crossed their outbound scales. Even though the truck I drove licensed for 80,000 pounds only – legally according to the bridge laws it could only haul about 74,000 pounds – but I was paid by the ton to haul and I rarely went out of any place under 100,000 pounds – more weight meant more money for me – as it will for drivers now.
Not only does an increase in gross weight limit destroy more roads – but also will increase roll-over type accidents. Tankers and flat-bed trailers as well as dump trailers have a “high” center-of-gravity which makes them easy to roll-over. Increasing the weight limits will only make this easier – which in-turn will increase accidents. This is something not mentioned – because there is not an easy way to “fix” this.
Some safety advocates say “stability control systems” could prevent trucks from rolling over. It is designed to “override” the system if a driver goes into a corner to fast. I say this is a disaster waiting to happen. Driving a tractor trailer with a “high center of gravity” you slow down before the corner and gradually power out “after” the corner. Nowhere is it mentioned how a “stability control system” would react to a bigger heavier load. So, with more weight comes bigger loads and results with more rollovers.
In reality all these states and the people who want bigger trucks and more gross weight on tractor trailers are only seeing one thing – dollar signs – more weight equals more money – to them not the driver. There is a bill that will actually put a freeze on the weight that is allowed to be hauled. HR1618 will keep the 80,000 pound weight limit as the legal weight. This is the bill that needs to be supported if you are concerned about safety out on the highway.
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