&gt; road taxes should be done for mileage as that more accurately measures their use and impact of roads.<p>Not at all. Axle load has a completely outsized impact on road wear. Civil engineers use a fourth power law to estimate road wear with respect to axle load: if you double the mileage you double road wear, but if you double the axle load (assuming constant axle count) the road wear is multiplied by 16.<p>Put in numbers, a Model S has an axle load of 1T (2T on 2 axles). A fully loaded 18-wheeler is limited to 36T (80000lbs) on 5 axles or a 7.2T average axle load. The road wear impact of the 18-wheeler compared to the Model S is 2.5 * 7.2^4 (2.5 times the number of axles and axle load ratio raised to the 4th power), or about 6700 times that of the Model S.<p>It&#x27;s actually slightly higher than that as 18-wheelers have 4 7.7T axles and 1 5.5 axle rather than 5 7.2T axles, the estimate is closer to 7500. Your standard 2T sedan has to drive for 7500 miles to generate the road wear a loaded 18-wheeler generates <i>every mile</i>.<p>Assuming your 2T sedan lives for <i>150000 miles</i>, it&#x27;s had the same road wear impact as <i>20 miles</i> of a loaded 18-wheeler.<p>When it comes to road wear and maintenance, mileage-based pricing and taxes are trucking subsidies.