These are super common - all of SFs MUNI system is built using the overhead wires -- batteries in the individual cars are interesting because there's a ton of c

These are super common - all of SFs MUNI system is built using the overhead wires -- batteries in the individual cars are interesting because there's a ton of cost involved in electrifying the entire length of the tunnel to deliver as much power as a train needs. All of the substations, the physical electrical cables themselves, etc add a ton of cost to tunneling projects and long-term wear items that will require endless maintenance that often shuts down the lines. Building a dumb cheap concrete tunnel and leaving the expensive parts in the cars themselves could be a very cost effective method of urban transport. Though I think the "use Teslas" is a dumb addition since a purpose built train car similar to the airport shuttles at Denver would be much more efficient and handicap accessible.