One tube or two? That’s a question Silicon Valley transportation officials as well as San Jose businesses and residents are asking about what’s the best way to drill a subway tube through downtown.

Just the fact that a newly developed single-bore tunneling technique would allow the proposed BART extension San Jose to be built with minimal disruption of traffic is enough to convince many of those affected along Santa Clara Street that one tube is the way to go.

It’s easy to understand why. Memories…