All three.

HSR and BART have unrelated goals and technologies. The law prohibits the use of HSR funding for BART. The main Caltrain right-of-way also serves freight trains, so that right-of-way will not be replaced by BART or a landscaped pedestrian and bike corridor. BART should run down 101 to Menlo Park (as proposed in 1999 Web Link and later connect to both Fremont and Santa Clara BART stations.

Caltrain should eventually be fully grade separated, electrified and have level boarding at every station. Some have proposed that Caltrain should be in a trench, with underground stations in Atherton, Menlo Park and Palo Alto. These underground stations would be expensive to maintain, attract the homeless, and be even more dangerous than 22nd Street Station (Web Link Anyone that has experienced the flooding of San Fransiquito Creek can understand why running an electrified train under that creek is a bad idea.

@we need both

I agree.

But let me add: HSR alongside the occasional freight train will be a sight to behold.

Caltrain today is extremely useful, but useful to the extent that there are limited alternatives. I take Caltrain to the city and then I walk 1/2 hour to the financial district (ok, you can also get onto Muni).

I'd go so far to say that BART could have two lines down the Peninsula: 101 and El Camino.

Having that first BART line along 101 would not be as expensive as HSR, but so much more useful to Peninsula communities. As a back of the napkin calculation, if HSR is 300 miles of track, and a BART extension is 33 miles, that's approximately a 10th of the cost. Much more bang for the buck.

That BART was proposed in the 1970's is irrelevant.

What's interesting is this bit of historic irony: In 1961 San Mateo County supervisors were pressured by David Bohannon not to pursue BART.

"1961: San Mateo County supervisors vote to leave BART, saying their voters would be paying taxes to carry mainly Santa Clara County residents. Real estate agent David Bohannon influenced the supervisors to drop out, fearing it would affect planned development along I-280."

See, Web Link and Web Link

Note that the David Bohannon mention above is not the present David Bohannon. The irony is that a BART line along 101 would benefit the future tenants, visitors and hotel at the approved Bohannon Menlo Gateway project.

I don;t mean to rehash the old stuff, but we now see how Menlo Park will change with additional office space, and how that additional office space will trigger additional housing requirements upon our city. In my mind, the only way to minimize the effects of all this, and perhaps lessen the housing requirements, is to have a new, frequent, public transit mode where that growth occurs. Dumbarton Rail is nice, but it's part of a solution, and A solution, or THE solution.

Correction:

"Dumbarton Rail is nice, but it's part of a solution, and A solution, or THE solution. "

Should be:
Dumbarton Rail is nice, but it's part of a solution, not A solution, nor THE solution.

Stu, Dumbarton Rail ( a Caltrain crossing the Bay on the old rail trestle) is an old argument and should be off the table. That is to say, the remains of the existing rail structure is not seismically worthy (divers checked the foundations) and would have be be totally replaced with a new rail bridge. Such a bridge would cost billions.

A BRT (bus rapid transit) solution to crossing the Bay on all four Bay bridges would go a long way to meeting public mass transit needs for a comprehensive, Bay Area wide public mass transit utility. And boy, we sure need that!

Oh, and Caltrain should be integrated managerially with the other Bay Area and regional rail transit systems. Right now there are around a dozen independently operated transit providers. There needs to be a single, comprehensive Bay Area, centrally managed, coordinated, urban public mass transit system.

Finally, HSR, whatever it is intended to be, will NOT be a public mass transit service. It will be a luxury train ride for the affluent, as it is even in "Communist" China. Remember, world-wide, HSR is the most expensive train ticket you can buy.

In the middle of our midpeninsula towns, the trains should be under ground. Other countries do this, and so do large cities in the US. Why not look ahead and realize it needs to be done eventually so why not now?
As others have stated in other threads, the ground-level land can be used for housing, new parks, fantastic north-south bike and pedestrian routes. These can further enhance the core of our towns while solving other issues that our built-out towns have.
BART functions quite well under the bay, so don't tell anyone that undergrounding can't be done or that a creek is too much an obstacle. That is pure nonsense and fear mongering.

BART is OK, but it doesn't solve the challenge of quick transit to San Francisco, as it still wanders around to 280 and back. Access to BART along 101 would require parking lots and stations where things are already built.

Atherton cannot find the resources to cover a drainage ditch along Marsh Road. Vehicles will continue to drive into that ditch and get stuck on the tracks in front of oncoming trains. The solution is not to imagine spending billions of dollars to construct three underground train stations, and a tunnel from Mountain View to Redwood City.

A little side note: there are some ideas floated for the "Dumbarton Corridor", i.e., the spur off the Caltrain rail line between Redwood City that connects to the old Dumbarton rail bridge. Without replacing the bridge (which would be terribly expensive), the corridor could be put to very good use to connect Belle Haven, Facebook, and other businesses in the M2 zone to downtown Redwood City and Caltrain. Idea floated include Caltrain spur, light rail, Bus Rapid Transit, or Pedestrian/Bike route. I'm a fan of BRT, as it's the second least expensive, flexible, and could be used to avoid the Marsh and Willow Road messes. (Light Rail might be tricky to deal with in downtown RWC, while BRT could use existing surface streets for the last half mile.)