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Friday, December 31, 2010

Trucks and roads

" The rule of thumb among highway engineers is that road deterioration is roughly proportional to vehicle axle weight to the fourth power. In other words, doubling the weight on an axle increases the wear and tear on the roads by 24, or 16 times. Roads are usually designed assuming that a single axle on a big truck carries a maximum of 18,000 pounds. Compared to a typical car carrying 2,000 pounds per axle, a fully loaded truck stresses the road surface 6,561 times as much. Minor overloading can make a big difference. Exceeding the maximum load by just 10 percent increases road stress by 46 percent — that's why you see all those weigh stations on highways."


Need I point out that if we just had bicycles on the roads, they would last a long, long time.

But wait, you say -- didn't they just have to repave the North Branch bike path? 

Yes they did, because of a notable error. The path wasn't engineered for the amount of truck traffic it gets -- mostly county trash collection and maintenance vehicles.   Government trucks weigh just as much as non-government trucks, pound for pound.

The worst path deterioration I saw was where the path goes at the south end of the New Trier West athletic fields, which means the path was likely used by vehicles trying to get closer to the fields.  Since they are athletic fields, one would think getting a little exercise on the way to the fields would be an attractive bonus.  But you would be wrong.