> the government is paying $0.84/mile for people to ride BART

If BART disappeared tomorrow, how much would the government have to pay to build all the additional roads and parking to support that incremental traffic?

And how much for healthcare for all the incremental pollution and collisions?

> several cents per vehicle mile

It's close to a dollar per mile when you include all the externalized costs.

Incremental property damage, injuries and fatalities, incremental chronic illness from pollution, parking land subsidy, fair market value of incremental land use and rights of way, lost tax revenue from that incremental land use, etc.