[da_chicken]

> We don't do this for gasoline

No, but commercial trucks use diesel, which carries about 25% higher taxes per gallon. And vehicle registration on semi-trailer trucks is significantly higher as well. They pay, on average, between $25,000 and $30,000 in taxes and fees each year.

> Turns out markets are pretty good when you leave them alone.

No, they aren't. They're ridiculously bad when you leave them alone because someone captures the market, ramps up anti-competitive practices, and immediately begins rent-seeking as hard as possible.

Free markets are pretty good at finding good prices. Markets that are left alone do not remain free. That lauded "self-interest" encourages businesses that have reached nearly 100% market share to increase profit in other ways.

[cma]

Heavier commercial trucks that run on diesel tend to cause more damage. Scales with roughly 4th power of axle load.

[AnthonyMouse]

That's a bad argument. There are gasoline trucks with a GVWR of ~20,000 pounds and diesel cars that weigh less than a Honda Accord. If you actually wanted to do that then you'd instead do something like tax based on axle weight and miles traveled, e.g. by reading the odometer during inspections.

The better argument is that diesel is worse for air quality and then it's a pigouvian tax in proportion to how much you burn.

The realpolitik argument is that fewer people have diesel vehicles and democracy is two wolves and a sheep voting on what's for dinner. But taxing commercial trucks is also a pretty sneaky way of taxing ~everything while pretending to not, so it's also the principal/agent problem. Legislators want to spend money while pretending not to take it from you.

[cma]

> diesel cars that weigh less than a Honda Accord.

It is taxed less than gas in lots of Europe where that is more common. You also need to factor in mpg vs gas, where it is higher, so more road-wear pCO2 was part of the debate in Europe, even though it is longer carbon chain so worse co2 ratio per calorie, the engines are more efficient. Diesel is worse for local air, better for long term co2.

There are a mixture of factors and lobbying behind the differencs, road wear is one. Farm fuel with no road wear isn't taxed much at all in lots of places and is more often diesel.

[AnthonyMouse]

> It is taxed less than gas in lots of Europe where that is more common.

But then it's even worse at recovering the cost of road maintenance from heavy trucks.

> You also need to factor in mpg vs gas, where it is higher

Passat TDI (diesel), ~3500 pounds, ~45MPG. Toyota Camry Hybrid (gas), ~3500 pounds, ~50MPG.

In theory diesel hybrids would be even more efficient but diesel engines and hybrid transmissions both add up-front cost and further efficiency improvements have diminishing returns because reducing a $100 fuel cost by 30% isn't as much money as reducing a $70 fuel cost by 30%.

> There are a mixture of factors and lobbying behind the differencs, road wear is one.

Road wear is the irrelevant one in terms of fuel. Because of the fourth power law, essentially all road wear is from full-size buses and semi trucks. The contribution from passenger cars and even the likes of diesel pickup trucks rounds to zero. Meanwhile the largest vehicles use a minority of the fuel because there are several times more passenger cars than semi trucks.

[AnthonyMouse]

"Someone captures the market" is the thing that happens when the government micromanages them. Laws that charge more per unit to high users aren't anti-trust laws. A farm doesn't have higher market share in food than Google has in a tech market just because it uses more water.

[jlebar]

> Free markets are pretty good at finding good prices. Markets that are left alone do not remain free.

OK but the market intervention being discussed here does not create a free(er) market. Its intent and effect is the literal opposite.