If anything, the load on transportation would actually go down. One of the big problems in Silicon Valley is that many of the cities (Palo Alto, Mountain View, Cupertino) are adding tens of thousands of jobs and hundreds of housing units. Which means that the only option is for people to either commute ever longer distances or crowd ever more people into the existing housing. And while it's not practical to bulldoze housing for even a 100% increase in density, there are plenty of single family houses that can be replaced with 6-10 unit apartment buildings. Even in SF itself.