I took one of these trains. The service was short-lived though.

It was called iDNight, by iDTGV, a former low cost high speed train operator in France. The idea was to run high speed trains at a slow speed during the night, turning a 3 hour trip into an 8 hour trip so that you can get a full night, and also so it can leave as the departure station is closing and arrive as the destination station is opening, therefore exploiting downtime, I guess.

These were not sleeper cars but regular high-speed train cars, not ideal for sleeping, but since most seats were vacant, at least in my experience, you could easily get two seats for yourself.

Since we're citing European trains, let's also cite European airports - I can arrive to the airport for an EU flight 20 minutes before take off and still have plenty of time to get everything sorted out. And I'm out of the airport within 15 minutes after landing - usually stepping right into a subway or something. I don't think it's such a huge margin if you fix your airports, which is going to be many orders of magnitude cheaper than building high speed rail from everywhere to everywhere.

> I can arrive to the airport for an EU flight 20 minutes before take off and still have plenty of time to get everything sorted out.

Maybe you can but none will recommend that you do, for example Paris recommends at least 2 hours [0]. And if you need to check luggage you have no chance if you're only 20 minutes early, on a train you just carry it onto the carriage.

[0] - https://www.parisaeroport.fr/en/passengers/flight-preparatio...

While i agree that EU airports are very efficient, 20 minutes before schedule take-off must be impossible. Surely you mean 20 minutes before boarding starts?

No, I'm usually the last person to board. Departure (but not arrival) frequently gets pushed back by 10-20 minutes, though I am making it on time even if not. I have literally never waited at a security check and it takes a minute or two to get through - speaking about EU flights.

There's no way you are not missing flights if you think you can get through security and to your gate regularly in 20 minutes.

Roughly every fifth flight they call my name, but I never missed a flight because of late arrival.

Do you only fly through small airports? I can't see how you would possibly guarantee not getting stuck in security at least sometimes

90% yes. I don't live nor work in the major hubs, sometimes I fly through as a stopover though (in EU you don't need to go through security again). I do this on purpose - often there are several airports about the same distance from my destination, so I just pick the least used one.