Thanks for stopping by.

Your issues are:

1) turnout speeds require that a train slowdown to exist the main track to the local loop.
2) Right of Way widths with 4 tracks.

Turnout Speed limitations
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You are correct that a train will need to slow down because of limitations on turnout speeds. However, this point is meaningless for these reasons:

* The speed through the east bay ( just like along the peninsula if the Pacheco Pass route is used ) will likely not be at maximum speed.
* Even if the train is running flat out. Based on my back-of-envelope calculations slowing from 220mph to 140mph should only require that the following train be 5 minutes behind (instead of 3 minutes behind). This is a minor scheduling issue and does not impact the following train’s speed.

Constrained right-of-way
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This is a red herring. The same “problem” only worse exists along the Caltrain ROW. But this does not seem to deter the California High-Speed Rail “authority” from deciding to drive the train through some very expensive real-estate. Most property bordering the train tends to be commercial anyhow.

In any event, 4 tracks requires only 80ft Right-of-Way, which is considerably narrower than many roads.

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The rest of your points fall into the category of interesting red herrings that do not pertain to the question at hand.

* “SNCF complain that pressure from local communities for more services to stop at their town, impedes them from running more efficient TGV services.” — So more people want the train to stop in their town… how is this related to the question at hand which is does the existence of a train station impact the speed of a train that is not stopping.

* “Reducing line capacity” is only meaningful if the traffic numbers warrant more trains. If the demand does not warrant more trains then the “reduction in capacity” is meaningless.

* Madrid – to – Barcelona observations: Interesting but meaningless. Missing data: When ? What time of day? Weekday? Weekend?

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My point is and continues to be: a freeway (or a rail system) can be engineered for higher speeds than possible for the current vehicles. China in fact is building their High-Speed Rail System to support trains running at 250mph anticipating that those speeds will soon be possible.

“Trains can skip stations! If a train doesn’t stop a station the existence or (non-existence) of a station is irrelevant!”

Trouble with this theory is a stopping train needs to slow down, thus delaying the train behind (or to think of it another way, using up line capacity). You can get around this by building extra long loops to allow the train to slow down off the running lines, but again this presents difficulties. The first is that the fastest speed that turnouts are currently rated at is 140mph (considerably less than even a 186mph line speed), so slowdown on the running line is still required for a stopping train. The second is that long loops mean four tracks in towns/cities, the very place where land use is both expensive and sensitive (more houses and businesses bulldozed).

SNCF complain that pressure from local communities for more services to stop at their town, impedes them from running more efficient TGV services.

“Running a train slower that system maximum because it is a “local” only matters when a higher speed express wants to pass.”

True, many countries (such as Spain and now the UK) run lower speed services over their HSLs. Unfortunately even when the ‘slow’ trains run considerably faster than most US services (generally 125-140mph), this dramatically reduces line capacity, which is meant to be a reason to build them in the first place. So a skeptic might argue that if you cannot fill a HSL with HS services, is there really a market for it in the first place?

To close, here’s an anecdote of some of my personal experience of HSR (it’s not meant to be a scientific comparison). I’ve stood by the Madrid to Barcelona HSL for hours and seen few enough trains to count on the fingers of one hand. By contrast, the day after I was standing next to LGV Meditereanee (France) watching flights of twin Duplex (i.e. double-decker) TGVs pass at six minutes headways.
If I were going to spend $30 billion on a high speed line, I know what I’d rather have.