UTL is about exploring past, present and future urban technologies in science and fiction, etc...
https://www.sfmta.com/projects/central-subway-project
https://www.sfgate.com/travel/resources/transit/article/what-could-bay-area-transit-look-like-in-2040-15104867.php
https://www.streetcar.org/what-might-have-been-geary/