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I-35W bridge collapse… No wonder 70% of the American public disapproves of truck weight increases.

American trucking grew up on a diet of auto subsidized roadbuilding, culminating in that transportation tour de force, the Interstate Highway System. While railroads were dragged down by overbuilt trackage and inefficiency, trucking cruised right by on cheap diesel at mile a minute pace and stole much of the railroads business. But those days are over, with no new Interstate System even in the planning stages.

Meanwhile, the American highway system is devolving and downright crumbling. In my home state, MNDOT is going through their planning process for the next couple decades, and they’re seriously damping down expectations. Even their most optimistic plans call for little added capacity, and they’re actually predicting highway deterioration, the only question is how much and where. To the west, despite South Dakota’s wide open weight limits governed only by how many axles you can put under a rig and how far apart you can get them, counties are being forced to post lower weight limits on bridges and roads. May explain why I’ve seen a few late model 9 axle double trailer trains for sale lately, and mere 80,000 pound 5 axle rigs are still a more common sight than the 20 axle 190,000 pound double trailer rigs South Dakota allows. With little political will to raise taxes to fund highway maintainence, never mind improvements, we end up with this: ImageMeanwhile, american trucking needs a weight increase- They’ve been stuck with an 80,000 pound weight limit on most highways for the three decades, and that was a slight upgrade from a 73,280 limit for three decades before that. Meanwhile, trucks have gotten heavier with emissions equipment, creature comforts, and “condo” sleepers tacked on because many trucking companies keep their drivers on the road for weeks and are too cheap to pay for even a cheap motel. That 80,000 pound limit translates to around 36 metric tons, and across the border in Canada trucks can weight 63.5 tons. In Europe the lowest weight limits run 40 tons, with bellweathers Germany and the Netherlands just rising above 50 tons while the Nordic nations have long allowed up to 60 tons. And while american truckers are stuck at 80 thousand pounds, Australian truckers can run at up to 85 tons on many routes, and the legendary outback roadtrains weight in at over 200 tons! Heck, with our low 80,000 pound weight limit and a semi tractor and skeletal container chassis weighting at least 26,000 pounds, most American highways can’t even handle a loaded to capacity 68,000 pound shipping container!

Yup, American trucking needs a weight increase… And fat chance they’ll get it!

Other day I was tipped off to a Federal Highway Administration (FHWA) study on the effects of increased truck weights on American roads. ‘Twas an exhaustive literature review of dozens of studies, and it weren’t pretty. The quick and dirty method of weight increases many truckers prefer, adding payload without adding more axles, in every instance dramatically increases road and bridge wear rates… It’s a non starter. The only way to increase weights without greater increases in road and bridge wear is to add more axles and even reduce individual axle weights, much like some western states have done with their “bridge formula” governed weights. That means longer and heavier truck and trailer frames and more axles, reducing the actual payload increases= Diminishing returns. And with little 4 laning of 2 lane roads that would allow longer rigs and higher weights, we’re stuck at a maximum length of around 80 feet. And no matter how far those axles and their loads can be spread apart, there’s still longer bridge spans of questionable strength that will dictate lower weights. We saw that on Minnesota state highways when the legislature allowed up to 97,000 pounds on 7 widely spaced axles, quicky tempered by MNDOT engineers sticking less liberal weight limits on dozen of bridges.

So run these trends out a few decades, and what happens… American trucking will continue to shrink and more freight shift to the railroads. Shippers, receivers, and towns with railroad access will benefit, and those without will shrink. Out here we’ve got a bunch of big food producers that literally ship out a semitrailer load of food to the coasts every few minutes… That’s not sustainable, and they’d be wise to procure some railroad sidings and refrigerated railcars ASAP.

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