Danger lurks with "Blended Rail": High Speed Rail (HSR) on Caltrain tracks. Forty-three auto/pedestrian grade crossings. Platforms with waiting Caltrain passengers inches away. HSR trains need secure (grade separated and fenced) track.
Far better: Upgrade UP's Mulford line long used by Amtrak from San Jose to Oakland, with a joint HSR/BART station in West Oakland. BART runs every few minutes to San Francisco and the West Bay, and frequently to East Bay BARTland.
Voila! No scarce HSR bond funds squandered electrifying Caltrain. No costly tunneling or terminal HSR facilities in San Francisco. No new trans-Bay tube needed to extend HSR to the Sacramento area. Gone are the hazards and operating problems of "Blended Rail."
Form a five-county BART district including Santa Clara and San Mateo counties. Plan to grade separate and convert Caltrain to BART (to Muni north of Millbrae/SFO); extend BART to the Golden Gate and Carquinez Bridges, to Brentwood, to Livermore, and over the Altamont. Then bring the plan and its funding to the voters -- like for BART itself five decades ago.
Robert S. Allen, BART Director, District 5 (1974-88); retired SP (now UPRR) Engineering/Operations