On the other hand, trucks are often speed-restricted and the tax might need to be on the order of $50k for a 60-foot truck (which would still equate to around $50 for a car). The costs would be passed down to all of the things that trucks are used for, so I suppose the average person wouldn't really pay any less for combined transport+groceries+fuel+household goods, but it might incentivize the use of smaller trucks with lighter axle loads, but that would also mean more drivers/poorer fuel efficiency/more accidents per ton per mile. At the least we should be mindful of the way that motorists are providing a subsidy to the logistics industry (which we indirectly benefit from, as well).

Dealing with government and taxes there is one additional factor to consider. The government can give tax cuts to targeted groups if they consider it beneficial to society.

So let say the truck has a $5000 tax to pay for yearly wear and tear on roads, but they also get a $5000 tax cut to reduce costs in the transportation sector. That will leave cars to still pay their road tax, even if in comparison they would be a tiny portion of the total road tax.