Recently in the SF Bay Area, there's been a lot of displeasure by transit activists that object to VTA's BART to San Jose extension (it's being built by VTA not BART) who had the choice between two tunneling options:

1. Two small-bore TBMs ~2 stories underground, one for rail in each direction. This would require cut and cover for the stations only

2. One large-bore TBM ~7 stories underground, with technically enough space to fit an entire station platform inside but displaces a HUGE amount of soil/rock along the entire line, and require very deep stations that take a long time for riders to enter/exit.

VTA consultants went with option 2 because they didn't want to disrupt the surface (again, only for the few blocks where the stations would be built) even though it costs $$ billions more.

Many transit activists (including me) are upset because it makes the project both take much longer and cost more. We could save money by literally just giving billions of dollars to the businesses on the affected blocks. There's no geo-technical reason to go with the large-bore option. This has also led to a lot of recent VTA-negativity among these activists.