I simply cannot see HSR sharing track with Caltrain between San Jose and SF working at all. There are only two tracks (North and South) and there is no room to build more. So it would seem that no high speed rail could go faster than caltrain on that segment and could not achieve the target travel time.
What I wish- although it may not be feasible- was a straight shot from Burbank to San Jose- as a single tunnel.
Caltrain has passing tracks at Sunnyvale and Brisbane. There are joint plans with CAHSR to add 4-track segments at Millbrae, San Mateo (between Hayward Park and Hillsdale), Redwood City, and Palo Alto (California Ave).
The Millbrae tracks are part of the new station design: they are removing one of the 3 BART tracks (superfluous because BART terminates at Millbrae) and using the space to construct two dedicated HSR tracks on the inside of Caltrain, as well as a HSR platform.
The San Mateo area is relatively straightforward: Caltrain already owns the land, it is currently surface parking lots for the Hillsdale station as well as the land used for the old station (which was moved a few years ago).
Redwood City is elevating the entire Caltrain/HSR track above the city as part of their grade separation strategy. The new viaduct will be built with 4 tracks instead of 2.
The only major sticking point is Cal Ave, where there is limited space and an unfriendly city.
5-6 passing track sections should be plenty for running blended service.
Ah, thanks for the reminder there are passing tracks already.
Are passing tracks really practical? Wouldn't they have to be extremely long to accomodate high speed trains mixed with local Caltrains? I have a hard time picturing this all working out even under ideal circumstances.
Usually they pass when the local train is at the station. This doesn't take all that much space; speed delta is 80mph (125mph once they grade-separate everything). Everything is computer controlled.
It occurs to me that this might be why they've chosen those particular areas. Sunnyvale, Redwood City, Hillsdale, Millbrae, and South San Francisco (just south of Brisbane) are all baby bullet stops, where all of the local, limited, and express trains stop, and so you can reliably count on every Caltrain stopping there and letting a HSR train pass. Cal Ave is the odd one out, but it still has local + limited service.
Caltrain has sections with four tracks. At these sections express trains overtake local trains. They did this improvement long time ago and called the service "baby bullet" back then.
It is an advantage that HSR uses Caltrain track to get to SF. It would be super expensive to build a separate high speed line, and it wouldn't be worth the time savings. Caltrain should spend money grade separating the whole line, adding passing lines where possible, and increasing the speed to 125mph or 150mph since it would be good for Caltrain service. At 125mph, HSR (250mph) would save 10 minutes, and 150mph would save 6 minutes.
> There are only two tracks (North and South) and there is no room to build more.
The SP/Caltrain/Bayshore-Cutoff line into SF used to be partially quad-tracked. It's easiest to see at Tunnel 2 just south of 22nd Street Station. The current two-track main uses one tunnel and there's a second tunnel portal blocked off next to it.
Ironically the Caltrain electrification project blocked it off even further by putting the supports for the overhead wires right where the other tracks used to be.
What I wish- although it may not be feasible- was a straight shot from Burbank to San Jose- as a single tunnel.