Road damage is proportional to axle weight raised to the 4th power. In the US, you cannot drive on the highways with more than 10 short tons (9.1 Mg) per axle.

Road damage is proportional to axle weight raised to the 4th power. In the US, you cannot drive on the highways with more than 10 short tons (9.1 Mg) per axle. If I cram my daily driver to the gills with heavy junk, I might have 0.75 short tons per axle. That heavily loaded cargo trailer is doing 30000 times more damage to the roads per mile than I am, specifically, and as much as 9600 average passenger cars. [0] Axle weight is not taken into consideration when I am taxed for the roads. Thus tax-avoidance behaviors optimize for the wrong variables. Drug dosages and adverse health effects are less easily modeled numerically. My concern is that if you tax something without understanding the potential consequences, you may end up doing more harm than good. [0] http://archive.gao.gov/f0302/109884.pdf http://archive.gao.gov/f0302/109884.pdf