It's an easily justifiable tax as well. Road wear scales to the 4th power of axle weight! Incentivise smaller cars, it means less road wear, higher fuel efficiency, and it's safer for pedestrians.
Interestingly, Rhode Island tried something like that. They had toll roads where only semis had to pay.
I thought the solution was a great idea. The cost is centered on the vehicles causing 95-99% of road wear in the state, by only charging a small fraction of drivers it reduces the overhead of the system from RI's perspective, and by only charging people who would have large bills it reduces the overhead from the perspective of the drivers being charged as well (if you pay a $3 toll and spend 5min handling the broken online billing portal after a billing letter was sent via a $0.63 stamp then that's a bit wasteful, but if you have a $100 toll the billing doesn't magically cost more, allowing the aggregate tolls across the state to be lower since they have a higher take rate). Plus, if it makes shipping more expensive, it transitively affects the people causing the most shipping instead of externalizing that to the other citizens, ideally causing a small downward pressure in aggregate shipping volume.
Anywho, it was struck down as unconstitutional. We'll see what happens in other places and times, but I don't have high hopes. At best we'll get a patchwork of special cases and exemptions that protect incumbants, don't fix the problem, and _hopefully_ don't inadvertently encourage even bigger vehicles.
This is not entirely true for consumer passenger vehicles, even ones weighing 7k pounds. There are many other reasons to tax but road wear is not as easily justifiable until you hit semi-truck weights. In general roads are made based on laden truck weights, the difference between a 4klb car and 7klb car does not make much if any difference.
I thought the solution was a great idea. The cost is centered on the vehicles causing 95-99% of road wear in the state, by only charging a small fraction of drivers it reduces the overhead of the system from RI's perspective, and by only charging people who would have large bills it reduces the overhead from the perspective of the drivers being charged as well (if you pay a $3 toll and spend 5min handling the broken online billing portal after a billing letter was sent via a $0.63 stamp then that's a bit wasteful, but if you have a $100 toll the billing doesn't magically cost more, allowing the aggregate tolls across the state to be lower since they have a higher take rate). Plus, if it makes shipping more expensive, it transitively affects the people causing the most shipping instead of externalizing that to the other citizens, ideally causing a small downward pressure in aggregate shipping volume.
Anywho, it was struck down as unconstitutional. We'll see what happens in other places and times, but I don't have high hopes. At best we'll get a patchwork of special cases and exemptions that protect incumbants, don't fix the problem, and _hopefully_ don't inadvertently encourage even bigger vehicles.