I honestly think the real toll is the mental concentration required and the stress caused by driving a car. Self-driving cars automatically fix that problem by removing the need for the passenger to concentrate on not killing people. When I take the bus I don't worry so much about my commute time, because I spend the ride relaxing and reading.

I think it is a both thing rather than an either-or thing.

As long as roads continue to exist in any form, it seems crazy not to aim for efficiency. What is to be gained by passing up opportunities to make them efficient?

So this is not a wrong metric, it is just that both metrics need to be taken into account.

I view maximizing car throughput as beneficial because it means less roads need to be built (more money for mass transit).