[buzzybee]

This has been proposed many times. Here is one plan from 1937 that would have been located where the Market Street BART tunnel is now:

http://blog.sfgate.com/thebigevent/2015/07/10/35-years-befor...

[internaut]

The future used to be much more interesting.

Check out Whale Bus:

https://upload.wikimedia.org/wikipedia/commons/thumb/1/14/Fr...