https://phys.org/news/2018-05-elon-musk-underground-la-tunnel.html

During the presentation in Los Angeles Thursday, Musk showed a video explaining the tunnels. Passengers would embark at ground-level into an 16-person shuttle—an elevator of sorts, which then joins a high-speed, electricity-powered network that travels at up to 125 miles per hour (200 kilometers per hour.)

The idea is for the vehicles to offer a service somewhere between riding a subway and traveling in a private car—and for just $1, passengers could reach downtown LA from its international airport in under 10 minutes.