What if we had a metro running along El Camino Real?
If you live along the peninsula, a lot of day-to-day life is along El Camino Real. What if we had a metro line running underneath it? A metro line much like what NYC and Paris have would make it relatively easy to go from street level to the metro. Stations could be at every major intersection.
One end might be downtown San Jose, then the line goes up El Camino Real. Since Caltrain already follows El Camino more or less from Menlo Park northward, most of the value of this metro would be between Palo Alto University Ave (with a shared station with Caltrain) and SJ. Given that, maybe this line just needs to be built between PA and SJ. If it's PA to SJ then it would be just VTA and one county, and not have the complications of multiple transit authorities.
And I imagine if this were built, then it would change the landscape of El Camino, with high density (mid or high rise buildings). Less need for car travel would mean less need to build parking.
What do you all think? Does anyone know if this was considered?
EDIT:
A few things I want to call out after seeing some comments:
Regarding the "but that's Caltrain" argument -- Why should we limit ourselves to one transit line (Caltrain) running up and down the peninsula? Manhattan has 4 subway lines running uptown <-> downtown. At some point if we want density (to solve the housing problem) we will need supporting transit. Also, Caltrain makes fewer stops and is better suited for covering longer distances (e.g. Sunnyvale to SF). I see this metro as a complement and supplement to Caltrain; at certain stops (e.g. University Ave in PA) you could switch to Caltrain and cover more distance faster.
Buses -- We have buses running on ECR now. What is their level of use? Are they a viable alternative to driving? I am looking at a job in downtown SJ and it would take me an about an hour to get there from Sunnyvale on bus 22 or 522. It's 18 minutes by car if I self-drive. It's just not compelling right now for people to not use their cars for trips along ECR. Perhaps BRT would work well, but why hasn't this been implemented yet?
Cost -- Yes, it will be expensive. It would have been better to build this 20 years ago, 10 years ago, etc. Not building it will come at the expense of quality of life.