I wonder how many passengers on that route are on connecting flights. HSR is likely to be an alternative for those who have LA or SF as destinations, but not for people traveling onward.

I don’t know why I did the math to answer your question, but I did. Please don’t upvote me, I don’t want encouragement for this behavior.

Apparently 1% of the total traffic in LAX in 2015 was for connecting flights to SFO [0]. Assuming this ratio didn’t change much in the following two year... considering LAX’s total traffic for 2017 was 84M [1] this means 840K people transferred from LAX to SFO. During 2017 3.5M people traveled from LAX to SFO.[2] This means about 24% of the traffic to SFO from LAX was for transferring flights. My numbers are clearly estimates because I couldn’t find a good record of every passenger itenary in the US which is what would be required for more the most accurate data. This also doesn’t cover passengers using SFO as a transfer station to LAX.

Interesting enough JFK to LAX has recently become the most traveled route in the US with 30K more passengers a year than LAX to SFO, which contradicts my previous statements. [2] It’s possible LAX to SFO has more total flights, if you assume shorter flights use smaller airplanes.

[0] https://www.anna.aero/2016/05/25/transfer-traffic-at-top-fou...

[1] https://www.lawa.org/-/media/lawa-web/statistics/market-shar...

[2]https://en.m.wikipedia.org/wiki/List_of_busiest_passenger_ai...

Granted this was 20 years ago, but I used to fly a fair amount out of the Bay Area. I don't remember ever catching a connecting flight at LAX. Usually it was one of Denver, Chicago, Salt Lake City, Atlanta[1] or Las Vegas.

One of the arguments I did read that was convincing is that Bay Area and LA basin airports are near capacity. Diverting passengers from the LA to Bay Area route would free up capacity for long distance flights. Thus alleviate the need to expand those airports. In the discussions I've had it's come up that expanding airports in built up areas is massively expensive. They want to add a third runway to Heathrow at a cost of £14 billion. That's 25% of the projected cost of CHSR.

[1] When you die, no matter if you go to heaven or hell you'll transfer through Atlanta.

The reason I was wondering is because I found I was transferring through LAX more than leaving the airport. Atlanta, of course, is a stopover almost every time I go to the South.

I suspect it may depend strongly on where you are going.

However when I did fly I occasionally went to a client in LA. Would fly in the morning and fly out same day usually. Back then from home in SJ to client in LA was about 2-3 hours all things included. If I had to do it via high speed rail probably would rent a hotel in Palmdale and ride the rest of the way in the morning. Then straight back the next evening. Unless ticking made that $$$