In reverse:

* Yes, a loop-back through station was originally a design option, it seems to have died somewhere early in the process, pre-2003. The tail tracks are shallow, cut-and-cover tunneling, I believe they will probably have had to bore to get a loop-back ... the loop-back would be extending well beyond the property being re-developed for the TBT project, so that would be much more expensive eminent domain for cut-and-cover on the turn.

And, yes, the original design spec was to stable four Caltrain trains, two per track ... they tend to run fairly short, but if they get to ten cars EMU, there's the capacity to hold a single full-length HSR set. AFAIU, they run the tail track through to a foundation of a freeway.

• I am unclear about the CHRSA demand for 400m of straight platform ... if I was to guess, I would guess that they can not provide detailed specification of what would be an acceptable platform curve radius for the extremes of the platforms (the middle portions are straight in any event because of structural support columns extending through the box to foundations beneath) and so are laying out an ambit claim that is on the safe side.

• On turn-arounds (that is, the Sidenote), once I hit arrival, tail, departure station and platform dwells that seemed comfortable to me as maximum allowables, I didn't press it any more. There's nothing I have heard about maximizing tunnel track throughput, and with 3 minute headways, that seemed to me on the access track to be 4 service slots, alternating between Caltrain and HSR, an open slot, repeated four times.

The alternation is because of the trainbox throat track design ... with independent egress track there is no need for Caltrain access to crossover HSR egress, and visa versa, so alternating HSR and Caltrain access means there is an egress slot for each service immediately preceeding each access.

* On Caltrain, I think its about 6 tph, but on the other hand, there are other standard gauge regional rail services being pushed for, and they would of course want to connect to Caltrain as well as to the intermodel (Bus at the TBT, BART a block away) transfers there.

The present Caltrain terminus at 4th and (mumble) would continue to be a Caltrain station, so if Caltrain hits capacity they can always start alternating between services terminating at the current terminus and services terminating at the TBT.


I've been accused of being a Marxist, yet while Harpo's my favourite, it's Groucho I'm always quoting. Odd, that.