Tolls were once difficult to enforce — collection infrastructure was expensive and slowed down traffic. Modern technology offers new ways forward, at the price of destroying privacy.

Or you could just impose a gasoline tax as a proxy for travel (oh hey that's exactly what they did.)

That works too, although if electric cars become mainstream, it would be an issue for the future.

It seems better to just tax something instead of setting up toll infrastructure

It really depends.

The free market is only efficient when transaction costs are low. For many forms of travel, the cost of monitoring such travel makes tracking far too expensive. Even just understanding a toll scheme has its own cost; you don't want to be too worried about misestimating the cost of every drive down to the grocery store.

For long-distance interstate travel, however, toll roads make a lot of sense. This is particularly the case where trucks are involved. You charge proportionally to axle weight, so the companies doing the shipping pay for the damage they are doing to the roads.

In other congested areas, tolls can serve as an effective form of rationing, particularly over bridges or through tunnels. This encourages more efficient resource usage, e.g. by making carpooling more worthwhile. This also makes more sense for city centers with congestion-charge fees. The alternative rationing scheme here, "sitting in traffic", is a very bad way to pay for things and imposes its own very high transaction costs.

A toll is a tax. Road usage isn’t equivalent, some roads are used more than others and at certain times. The goal would be to vary the tax based on demand, which is different for each road and time.

This already happens in many places, especially with tunnels and bridges.

> What is the problem with making all roads toll roads?

It's literally regressive.

Life is regressive. The only way to allocate resources efficiently is to charge what a thing costs to provide. (This often includes a modest accounting profit, consistent with the cost of capital, but never an outsized economic profit, consistent with rent seeking cronyism.)

If life is too hard for people with less money, society should decide how much money to give everyone to make it better, and then let them make their decisions -- instead of declaring, "Passenger Vehicle Traffic And Parking Lots Are Virtuous And Worth Subsidizing."

Sounds inefficient and complex to me to give people money just to take it away again. If you don't make people pay tolls you don't need to give them money to pay the tolls. Cover it all with income tax.

The problem is that when driving is free, people end up doing much more of it than is efficient. So instead of paying the congestion charge, you "pay" by sitting in traffic. Are you being responsible about resource usage and carpooling? Too bad, you still pay the exact same amount of delay. (HOV lanes do mitigate this, but only on those corridors where they're available.)

Meanwhile, the government generally ends up building too many roads and not enough transit. All this easily overwhelms the other inefficiencies.

Other bad plans where we don't charge for resources: Let's give all the people free electricity, so poor people don't have to pay something regressive! Then a few jerks can use it to mine Bitcoin until there are brownouts everywhere.

Road capacity is a limited resource. You can't just keep increasing income tax indefinitely to keep covering the ever increasing usage. The goal is to reduce usage, and/or time shift it.

So reduce taxes for poorer people. Or give them credits for tolls. The point is road usage isn't free, and pretending it is causes problems elsewhere.