horrible to come back to the states after becoming acquainted with the paris metro & friends

Took it for a few years too, I think the frequency can be as much as every 90 seconds.

Yep, I live on it and 2 minutes is underselling it.

On the central trunk frequency in rush hour is a departure every 90s, which means there's almost constantly a train at the station.

This reminds of the way the S-Bahn system works through central Berlin. Several different lines all converge on the same route through the heart of the city, providing "adequate" service intervals to their actual endpoints, but as a side effect, 90 sec departures in the city itself.

It's like a magic trick!

That's not how the RERs work. The only shared track between any RER lines is the short tunnel for the B and D lines between Chatelet - Les Halles and Gare Du Nord. There have been many plans about doubling it, but it would be extremely expensive because it's under one of the densest and oldest parts of the city, and cross multiple metro lines, and connecting to two of the largest transit hubs in Europe and the world outside of East Asia.

Every other line has dedicated tracks. There can and often are branches, but usually they're 2-3 at most per "side" of the central trunk, with the exception of the unwieldly spaghetti that used to be the RER C between the simplification of it, which reduced it to three branches per side as well.

* RER A in question has two branches to the east, and three to the west.

* B has 2.5 to the south and 2 to the north

* D has 2-3 to the south and one to the north

* E has two to the east, and for now one to the west (I think there will be 1.5 in the end when it's all finished)

So not at all comparable to the S-Bahns that more often than not get all forced into a single tunnel resulting in atrocious frequency on the branches. As an example, frenquency on the branches in rush hour on the A is 5 minutes at most on the least frequented branches. At the worst of times, late at night on the least frequented branches of the least frequented lines you're looking into 20-30 minutes frequency, which isn't great, but isn't terrible either for a station in the middle of nowhere far away on the C, D or E.

> 5 minutes at most on the least frequented branches

I suppose I should say at this point that I live in the USA. And not only in the USA, but in New Mexico :)

> late at night on the least frequented branches of the least frequented lines you're looking into 20-30 minutes frequency

Ditto. This doesn't sound that different from what I remember growing up on the Central Line coming in from the NE of London. Doesn't sound that bad, though more is generally better, I suppose.

Yes, but they realized that at that point the problem is no longer the trains but people. You can't reliably board people that fast. IIRC, they moved from theoretical every 2 minutes to theoretical 2 minutes 30, and largely improve their throughput. But yes when there is congestion trains can go faster than 2 minutes 30 when relevant.

Thanks to the SACEM automation system (with dynamic blocks) you can have a train arriving at the platform while the previous one is departing, it's pretty impressive.

Here's an example... from 12 years ago: https://www.youtube.com/watch?v=oCj0yQacKVE

Nowadays these older trains have been deprecated and only double-deckers run the line.

Not sure about RER, but if my memory is good, during RATP strikes in 2019, the automated line 1 was running every 60 seconds or so.

Paris has such a good public transport system, and now also cycling infrastructure, that something like 50% of young adults (<30y) don't even have a driving license !

AFAIK the world record for this is held by Moscow, where some lines run every 80 seconds in regular schedules operation. That's departure to departure, and it's virtually impossible to go below that, because the speed of humans boarding becomes the limiting factor. Some automated lines claim 75 seconds as a theoretical limit, but AFAIK nobody actually does this.

Intersting, I've just googled a bit, and Ligne 1 in Paris was running every 90 seconds in peak hours, most other lines are around 100-110.

the further away you are in your commute in the RER A the worse it is. the segments handled by SNCF (beyond nanterre) are a real pain where they left me stranded when they broke down and they do that more often than you would like. bus, uber, etc no longer work at that moment because well all the passengers flock to them and they don't have the capacity. I happened so often that ended moving to the center of paris just to avoid it.

It's due to a lack of maintenance in the 90s. Here a video in french that show why there is so much maintenance work to do right now: https://www.youtube.com/watch?v=hWNc4QgHrQ0