The Limits of Regional Rail
I recently found myself involved in a discussion about Boston regional rail that involved a proposal to do more thorough regional rail-subway integration. Normally, S-Bahn systems mix some aspects of longer-range regional rail and some aspects of urban metro systems. They provide metro-like service in the urban core – for example, Berliners use the the three trunk lines of the S-Bahn as if they were U-Bahn lines. But, unlike proper metros, they branch in the suburbs and tend to have lower frequency and lower quality of infrastructure. However, there is a limit to this integration, coming from timetabling.
The characteristics of metro-like S-Bahn
When I call some S-Bahns, or some S-Bahn trunks, “metro-like,” what I mean is how users perceive them, and not how planners do. A metro line is one that users get on without concern for the timetable. It may run on a clockface schedule, for example on a 5-minute takt in Berlin, but passengers don’t try to time themselves to get on a specific train, and if the train is 1-2 minutes behind schedule then nobody really minds. This user behavior usually comes from high frequency. However, in New York, despite extensive branching and 10-minute frequencies, I classify the subway as fully metro-like because the trains are not dispatched as a scheduled railroad and even if they were, passengers don’t ever think in terms of “my Queens-bound N train arrives at :06 every 10 minutes.”
S-Bahn lines have trunks like this, but also branches that work like regional rail. The regional rail pattern in the sense of RegionalBahn is one in which passengers definitely look at timetables and try to make them, and connecting public transit lines are planned to make timed transfers. On lines branded as RegionalBahn service comes every half hour or every hour, and usually S-Bahn tails are every 15-30 minutes (occasionally 10), but the printed schedule is paramount either way; when I rode the RER B to IHES in the last three months of 2016, I memorized the 15-minute takt and timed myself to it.
The key aspect of S-Bahns is combining these two patterns. But this leads to a key observation: they have to interline a number of different service patterns, which requires planning infrastructure and service to permit both. They can’t run on pure headway management in the core, because the branches must be scheduled. But they have to use a timetabling system that permits high core frequency nonetheless.
Finally, observe that I am not discussing the type of equipment used. A subway train that extends far into the suburbs may qualify as regional rail – the Metropolitan line in London qualifies as an example on account of its highly branched service pattern in Metro-land. In the other direction, a train built to mainline standards that runs consistent service pattern with little to no branching at a range typical of metros is not, for the purpose of this issue, regional rail – examples include the Yamanote and Keihin-Tohoku Lines in Tokyo, which run identical trains to those that run deeper into suburbia but have literally no (Yamanote) or almost no (Keihin-Tohoku) variation in service patterns.
The limit of interlining
A large degree of interlining tends to reduce timetable reliability. Trains have to make junctions at specific times. This is compounded by a number of different factors:
1. Trunk throughput
The busier the trunk is, the harder it is to keep everything consistent. If you run 15 trains per half-hour, that’s 15 opportunities for a 2-minute delay to mess the order in which trains arrive, which has implications further down. If you run 4 trains per half-hour, that’s 4 opportunities, and a 2-minute delay is easily recoverable anyway.
2. Trunk length
Longer and more complex trunks introduce their own problems. If many passengers treat trains as interchangeable and don’t care what order they arrive in, then this may not be good for timekeeping – a slight delay on a branch may lead to grossly uneven headways on the trunk, which compound on busy metro lines for similar reasons as on buses. Berlin’s Stadtbahn has 14 stations from Ostkreuz to Westkreuz counting both, and this may make the branches with their 20-minute frequencies a little too difficult to fit together – evidently, peak throughput is 18 trains per hour, hardly the cutting edge. The RER A has 7 trunk stations from Vincennes to La Défense inclusive, and around 27 peak trains per hour.
3. Branch infrastructure quality
In the limit, the branches have to have excellent infrastructure quality, to be resilient to 1-2 minute delays. Timed meets on a mostly single-trunk line, routine on 15-minute branches like some lines in suburban Zurich and Tokyo, become dicey on lines that feed very busy trunks. Tokyo does this on the Yokosuka Line, which is far from the busiest (it peaks around 20 trains per hour) and Zurich on the right bank of Lake Zurich, which feeds into an S-Bahn trunk with 4 stations inclusive from Stadelhofen to Oerlikon. The busiest S-Bahn lines tend to have all-doubled outer ends.
4. One vs. two ends
If the line is single-ended, then inbound trains can just run metro-style in city center without regard for the printed schedule, use the terminal for schedule recovery, and then go outbound on schedule. Non-through-running lines are by definition single-ended, and this includes what I believe is Tokyo’s busiest regional rail line, the Chuo Rapid Line. But even some through-running lines are de facto single-ended if demand is highly asymmetric, like the Stadtbahn, which has far more demand from the east than from the west, so that one branch even turns at Westkreuz. Double-ended lines do not have this opportunity for recovery, so it’s more important to stay on schedule, especially if the end is not just busy but also has extensive branching itself.
Pedestrian Observations 
BART’s suburban branches clearly fall under your definition “regional rail” given the 15 minutes (at best) frequency per service, with some branches having more than one service. Before the extension from Colma to SFO/Millbrae, it would also clearly be singled-ended, but I’m not sure if sure if that’s enough to qualify as being double-ended now.
Actually, BART runs about 24 trains per hour through the tube, so it’s closer to a train every 10 mins, although not eventually distributed between the lines. Pittsburg-Bayshore line runs much more frequently – some trains are turned at Pleasant Hill in East Bay and 24th Street in SF. The contract was only awarded in January, so it’ll be a while before full capacity is realized. They need new train cars to reduce dwell times with 3 doors and 2 more power stations in downtown SF to power the extra trains.
Yeah, but that’s Ellen’s point. From West Oakland to San Fransisco, it acts like a metro, with frequency good enough to ignore the schedule. But out on the suburbs on the blue or yellow branches, folks always look at the schedule. It is regional rail.
I remember the first time I took BART out to the ‘burbs. I forgot to the check the schedule and just missed my train back into the city from Walnut Creek. I stood along on the platform for ~12 minutes, and then right before the train arrived there were like 30 people ready to board the train. In other words, it felt exactly like regional rail.
I think it’s single-ended given how little ridership there is on the West Bay side (esp. south of Daly City, where the branching matters).
Yeah, I’d agree. And I have first hand experience in how weak ridership along the SFO extension can be. As much as people thrash the zoning of area, the shit station placement made things even worse.
Is the throughput of trains on a trunk really as much of a function of station number as you seem to think? Could RER’s better train throughput numbers not be due to the better signaling system? Or does the Berlin S-Bahn use moving blocks? Though it seems like another possible source of trunk complexity, branches entering the trunk at different places, would be a source of unreliability and low throughput.
I think Berlin has moving-block signaling too on the S-Bahn trunks but I’m not sure. Regardless, fixed-block signaling systems very easily do more than 18; the RER B alone has 20 despite asymmetric track-sharing with the D, and IIRC the RER A got 24 before SACEM was installed and let it do 30 (before the recent curtailment to 25-27 because dwell times). It should be possible for Berlin to do at least 24 if it gets rid of the reverse-branching, even with long trunk lines.
The worst case is if you have a double-ended line that combines a scheduled railroad with one that isn’t. The Boston case I alluded to in the lede is extending the Red Line over the Old Colony Lines; it’s attractive and Tokyo would 100% do that, but you’re then forcing the Ashmont branch and a bunch of suburban branches with single track to share tracks, and it’s a double-ended line because actually there’s (slightly) more overall traffic into the center from the Cambridge side than from the Ashmont/Braintree side, and unless just about everything on the OC side gets doubled, delays will cascade.
The Rotterdam metro is also limited to 18tph on the trunk lines for similar reasons. It’s a really interesting network, have you ever read about it? In the east of Rotterdam it’s a typical Stadtbahn, with surface stretches running into a city centre tunnel. In the south and southwest, it’s elevated metro, and there’s reverse branching between the NS and EW tunnels. On the north towards the Hague it runs on a former mainline railway, interlining with Zoetermeer trams (also on former mainline track) in the Hague. They just opened a western branch on former mainline track, where freight runs midday, forcing single track metro operation.
Then there are some silly decisions that mean they run 85 metre trains on a network that originally had 120m platforms, while newer ones were built to 90m (on the surface light rail section and on the former railways, which used to be longer), leading to capacity issues because of the limited frequency.
I haven’t! What should I be reading about it?
American Stadtbahn systems cram pretty high throughput through central trunks, like 30+ tph in Boston, but they’re all single-ended and don’t care about any scheduling on the surface branches.
I mean if you want to hear really stupid train shortening stories, East Rail in Hong Kong (the oldest railway and the former “Kowloon Canton Railway”) is *finally* being extended under Victoria Harbor to the CBD on Hong Kong Island, but despite adding an extremely high-demand link (the existing Tsuen Wan line running mostly the same route has a capacity of 75,000 per hour and people wait for multiple trains during rush hour to pass), because of financial engineering they’ve also shortened the very long trains on the East Rail Line from 12 to 9 cars, because they didn’t want to spend money on platforms and more egress.
And this after they axed two stations on the link serving busy areas to save money, as well.
I thought they have decided to make a last minute attempt to extend the platforms at Admiralty station to accommodate 10 cars though plans have already been made to deliver 9 car trains to start the service. That is some serious screw up on the planners end considering the line is already overburdened. Their excuse was not enough land for 12 car platforms at the terminal station in Admiralty thereby dictating the train lengths for the entire line. They plan on compensating for the lost capacity with increased frequency from the current 20 tph to possibly 24 tph with the CBTC signaling upgrade.
One quick way for MTR to increase capacity would be to get rid of the space wasting first class car and it’s added layer of admin complexity. The thinking behind it was to provide an alternative to those would could afford to pay double fare for more space complete with transverse seating as opposed to the longitudinal seating of the other cars, yet the car still gets packed to uncomfortable levels. If its going to be crowded regardless, they might as well eliminate it. But then they’ve already ordered the capacity-wasting-dwell-time-increasing cars which have 2 doors instead of the usual 5 doors.
Shenzhen metro group thought it was a brilliant idea and decided to replicate it on Shenzhen metro line 11 but went a step further by making 2 cars out of 8 cars “business class” and charge 3X the fare instead of 2X for MTR in Hong kong. Suffice to say, the cars often run empty while forcing more crowding on the other cars. https://www.chinadaily.com.cn/china/2016-08/22/content_26556447.htm
The first class cars of ex-East Rail SP1900 trains are being sent back to Japan for conversion into regular cars for the TML, it was just a matter of swapping out the seats and removing panels blocking the extra doors.
For the new Rotem trains, it appears the same applies – the doors of the first class cars line up with doors 2 and 4 of regular cars, and the extra doorways are plugged with panels and can probably be removed pretty quickly. Platform doors, however….
At least during the KCR days it was a legacy of the line being, you know, an actual British railroad. It became rather pointless for commuter services, though.
Aren’t these criticisms a bit excessive? Since 1910 this was an international railway linking to Shenzhen and Guangzhou and other mainland destinations as far as Shanghai and Beijing. Not Metro. Remember what its name stands for, KCR: Kowloon-Canton-Railway. It is normal for long-distance trains to have two or more class seats/carriages. Isn’t it a bit like saying Eurostar should abolish its Business Class? It is only recently that it was merged with MTR and this connection to Admiralty represents its conversion to Metro. And so it is converting the First Class carriages. All the rest of MTR network trains are 8 carriages max. While budgets may be part of the story, I don’t find it difficult to give credence to the constraints in Admiralty: Hong Kong is one of the most physically, geographically constrained sites to construct things in the world, and there are 3 MTR lines converging at Admiralty which is also land reclaimed from the sea.
I don’t quite understand what happens to the international pax unless they are run as special trains on the same track as Metro trains? Unless all has switched to the HSR station/train at West Kowloon but it seems unlikely that they would abandon one of the two border crossings (excluding road-only HK-Zuhai-Macau bridge). Or are they no longer thru-trains and international pax change at the border?
@michaelrjames
Yes, international trains are special trains that run without stopping from the border all the way to Hung Hom. You’ll find them on the China Railway timetable, and for the most part they use China Railway locomotives and carriages.
The current 12-car trains only operate up to the Chinese border at Lo Wu and Lok Ma Chau, which is only a 45 minute trip. There’s no reason for there to be first class on a line shorter than several subway lines elsewhere. 12 cars, though, has to be a thing because many Shenzhen folk prefer to go to Lo Wu by Shenzhen Metro and cross the border on foot, instead of using the international trains.
For what it’s worth, East Rail is being upgraded to a CBTC signalling system.
@michael: yeah, the “CR” part of “KCR” stopped being a thing in 1949, at which point the border was closed and then the KCR was an end-to-end 45 minute journey serving mostly rural areas, and then British-style new towns. At which point offering a first class service on a short commuter service was quite silly. First class on RER A, as a comparison, would be a stupid waste of time and space.
Even after the border reopening in the ’70s, only a few trains an hour, if that, were nonstop long-distance trains from Hung Hom. Usually people using the East Rail Line for cross border services would just go to Lok Ma Chau or Lo Wu and cross the border on foot, because the frequency is much higher and the intercity train only really makes sense if you’re a reasonable distance from Hung Hom, which most people are not. (Also until recently anything much farther than Guangzhou was a much more reasonable plane journey. Even with the massive HSR system Beijing-Hong Kong or Shanghai-Hong Kong is a very long journey at 8 hours.)
@Henry
Depends on one’s view of “reasonable”. Yonks ago I did Beijing to Hong Kong using the overnight sleeper train. You went thru immigration control in Guangzhou; you had to de-train with all luggage, cleared C&I, then reboard the same train (I think) for the leg into HK. Good trip, though on balance I would have preferred a daytime journey because the o/n was mostly in darkness, although it has the advantage of another full day in Beijing without paying for an extra night in a hotel. It was an add-on to the Moscow-Beijing TransSiberian so I vaguely recall there was no choice. Last trip to PRC I flew HK to Shanghai but these days I’d be happy to take the HSR.
@Henry
Forgot to add: at one point, many Metros had two class carriages including London and Paris. Paris operated up to the 60s at least, possibly into the 70s? I doubt the RER ever did but its precursor suburban rail possibly did.
I remember 1st class in the métro in Paris in the 80s. From the video at link below, it was removed only in 1991 and 1999 for RER and trains de banlieue. They also claim that Paris métro was the only one in the world with 2 classes in 1991.
https://www.leparisien.fr/archives/le-jour-ou-la-fin-de-la-1ere-classe-dans-le-rer-31-08-2015-5049497.php
Memory plays tricks on us, but seriously do you remember First Class on the Paris Metro? I lived there in the 80s and I’m pretty sure I would have known and remembered. Possibly it survived on one line somewhere–maybe the bis lines which always seemed like stepping back in time. Maybe those are the dates when official or legal rules made it permanent but I am very sceptical of the claims.
I suppose this will seem like very dodgy evidence but in a relatively modern film, a comedy of social moers, Le prix à payer (2007) (The Price to Pay) about a wealthy businessman and his idle entitled wife (played by Nathalie Baye), in one scene she gets trapped in the city when discovers the husband has cancelled all her credit cards so she is forced to use the Metro and at the ticket booth she demands a first class ticket and the server tells her that they haven’t sold those since …. (and here I can’t be sure but I think it was something like 1971).
But maybe I have it wrong. BTW, that le Figaro had a link but it didn’t lead me anywhere (though I have extremely low patience with that kind of link that forces you to search and search …).
As for the RER, I’m quite sure the RER-B didn’t from the early 80s but who knows about, say, RER-C which was little changed from its suburban rail days–and perhaps retained it to milk the tourists? But again, I doubt it.
Needs more definitive evidence.
OK, some ancient bits of my cranial RAM are being accessed for the first time in many decades! I think I now understand. As some of the citations below indicate, the 1991 date may be when parliament actually legally eliminated the practice on RATP, it seems like it mostly faded, including officially, from 1981 if not before. All of the (minimalist) articles on the subject clearly use photos from long before this to illustrate the First and Second class carriages (they look pre-war to me and I certainly never saw anything of that ilk from my first trip to Paris in ≈1980). But I now do vaguely recall the colour-coded carriages (yellow for 1st, but I remain unconvinced there were any on my main #7 line which had the most modern trains, and was all-blue IIRC) but no other markings, and by the time I went to live there (mid-80s) the distinction was both subtle and barely acknowledged. Also, I excuse myself from not knowing or forgetting because, from the 70s, it applied only during peak hours (and working week) which I rarely used, and was officially relaxed with crowded trains by 1981. Some have pointed out that the change coincided with the first socialist president (Mitterrand, elected 1980).
and:
As I mentioned above, the 1st cars were yellow by the 80s, but almost all media pics resort to museum pieces (like below) in which it was red while the regular cars were olive drab. Comments reveal that the original 1st had cushioned seats while 2nd had bare wooden ones; again by the 80s this distinction had long gone and all seats were cushioned.
I’m now having a doubt, I was quite young then and rarely taking the métro during holidays in Paris. But I found this TV news report from 1991 where you can see the 1st class wagon like I remember, always in the middle of the train with a yellow line at the top. It was indeed accessible to 2nd class ticket holders in case of rush so yes the difference was probably not that obvious.
https://m.ina.fr/video/CAB91036035
For the RER, I don’t remember even though I took the RER C quite a few times in the 90’s. Here below is another link to the video previously mentioned.
Right.
Previously I said that my line #7 didn’t have yellow first-class cars because they were all of the modern type. And they didn’t … but then I thought it was unlikely to be an exception because they would have to make it system wide. On trawling the memory banks more, and being nudged by that vid with the carriage with the yellow racing stripe, I reckon that was what even the modern trains had. That is, it was pretty subtle, and I suspect made like that from the 70s as RATP realised it was probably going to disappear before too long (and this would just involve a very minimal bit of painting, or maybe even peeling off that stripe!).
Berlin most certainly doesn’t have moving block. They’re only just now replacing the old mechanical train stops with something more modern, but even that is rather for safety (continuous supervision of permitted speeds and braking curves when approaching restricted signals) than for capacity reasons (the new system is balise-based, i.e. no continuous communication between signalling system and train protection), and the underlying signalling system (fixed blocks with colour-light signalling) remains the same.
The trunk in München is rather long with very busy stations. The “regular” throughput is 24 tph. I remember reading a couple of years ago that they now run the trunk “metro-like” and sort out the delays on the outer branches.
About Zürich: they operate 15 minute intervals over single tracks (in one place 6 tph where a local immediately follows / precedes the 15 interval express). The most complex pattern is, however the SZU (lines S-4 and S-10), which at peak run at 10 min intervals. The “speciality” is the different voltage of the two lines (S-10 is 1500 VDC, with off-center wiring). Smartly placed changeovers allow an overlaid 10 minute interval on essentially two single-track lines.
How do they maintain 20-minute takts on the branches in Munich? A few still have single track or shared service with non-S-Bahn trains. Or do they use Ostbahnhof turnbacks to pad the schedule?
Most lines are already double-tracked. Otherwise, they may have some double track segments, or a relatively loose schedule, allowing meets at given stations, all 10 minutes apart. They also have some branches where only every other train goes to the far end, reducing the number of places to meet.
There are two lines changing direction at Ostbahnhof and (I think) one which ends there.
The way engineers in Cologne plan to solve the reliability issue is by constructing two additional plattforms in Deutz and Hauptbahnhof (and possibly Hansaring). In Cologne, whoose expanded S-Bahn network will be almost 100 % above ground, the Stammstrecke/Trunk line is short and only encompasses Deutz, Hauptbahnhof and Hansaring.
On those stations, in case of a delay, an S-Bahn will then use the other platform for its direction.
The outbound lines definitely fall under the Regional S-Bahn paradigm, as most will have 20′ frequencies and go far into the wider region,.where they replace diesel Regionalbahn services on 30′ takts after the lines have been electrified and upgraded to fit the new schedule.
How much does flying junction vs level function changes to reliability and output?
Considerably. I’d say it increases capacity by at least 50%.
CTA says 30% for the Red Purple Bypass (and this is a single flyover track): https://chicago.suntimes.com/2019/8/1/20751090/new-red-purple-bypass-will-reduce-cta-congestion-but-neighbors-worry-about-disruptive-construction
That is a somewhat pathologically bad case where trains need to cut across four tracks at once, and it’s at a bottleneck of 3 busy lines at peak times. But I’ve actually heard it will more like double throughput at rush hour.
I think the 30% figure cited is only for red line trains. You should see some uptick in brown and purple line trains that may very well get you closer to 50%.
Ueno-Tokyo Line is an example exacerbates all of these issues by adding tons of through-running trains that would formerly terminate at Ueno or Tokyo. A substantial fraction of them now run up to 150-200km one way. Delays are surprisingly frequent as incidents in far away branches now propagate much more easily.
Yes, but this is old news- the Shonan Shinjuku Line faces/faced the same problems, and that line was opened in 2001. To JR-E, the benefits of such an operation outweigh the drawbacks. In the Ueno-Tokyo Line case, the through running alleviates the excessive AM peak crowding of the Yamanote Line between Ueno and Akihabara. The priority/mandate of JR-E (as well as the city of Tokyo) is to reduce rush hour crowding of commuter trains, and has been since at least the 1980s. Furthermore, the Ueno-Tokyo line affords a direct link from the government and commerce centers of Minato Ward (Shinagawa Station) and the Marunouchi district (Tokyo Station) to locations in Ibaraki Prefecture via the Joban Line.
That, and it appears to be that Japan doesn’t care so much about frequency, preferring to use sheer brute force (ie. massive trains) to achieve capacity goals. It would help that a lower frequency would give them more space to sort out disruption too.
If they went with the Western “frequency is king” mentality, you wouldn’t have all those cases of extra 4/5 car sets being tacked on before a train enters a congested area.
Shonan-Shinjuku Line is worse due to Yokosuka Line and Saikyo Line. Ueno-Tokyo Line’s Joban Line service has complaints for relatively empty trains compared to the major Touhoku Line, while especially Hitachi and Tokiwa Limited Express to the Shinagawa Station interchange/hub is promising.
As a side note, there’s some relation between the two on the yet to be realized Soutetsu service. Trains are only diverted to terminate at Shinagawa Station in disruptions.
Since comments mentioned grade-separated junctions, I might as well name one culprit being Hebikubo junction where the Oosaki branch with Yamanote Freight Line crosses Hinkaku Line at-grade
With the increased risk of delays on a double ended trunk compared to a single ended trunk, is it still valuable to have through running like Paris and Tokyo instead of two single end trunks back to back without through running like Chicago?
I can only speak for the Japanese experience, but the answer is undoubtedly yes. As in the Ueno-Tokyo Line case mentioned above as well as numerous other projects since the sixties. The most recent is the Sotetsu-JR (opened last year) and Sotetsu-Tokyu link (opening FY2022) via the Hazawa Yokohama Kokuritsudai Station junction. This run-through operation was primarily driven by Sotetsu’s desire to divert heavy Tokyo-bound commuter traffic from its congested stub end terminal in Yokohama to a bypass route, and to attract new residents to the Yokohama suburbs where it owns real estate. Of course schedule disruptions are inevitable, but seem to be accepted and addressed as best as possible through various mitigation efforts.
Japanese trains are ludicrously reliable however. Much more so than European ones. I’ve made tight 5 change journeys before.
The way to think of this is that you’re not so much “double-ending” a trunk as providing multiple turnback locations for each trunk.
Without hugely expensive fly-overs/dive-unders in the approaches to turnback stations, every added turnback platform at any one station is of reduced utility, as trains reversing there will have route conflicts with each other across the flat junctions.
In contrast, a single turnback platform further along the line (“past” the “terminal”) has maximal reversals-per-hour capacity, since there is no other train in conflict.
More turnback locations will provide greater trunk throughput than the same number of turnback platforms at fewer stations. These can either be branches off the far-end trunk, or “inline” (central turnback tracks between the through tracks) along the far truck.
Obviously this is a toy model, and there are other factors at play (matching train capacity to demand, just for starters) but it shows that even a bit of through-running can gradually siphon off turnback demand that can overwhelming expensive — as well as diminishing-returns ineffective — to attempt to accommodate at a single CBD terminus station.
“Double-ended” demand is generally asymmetrical, but that doesn’t mean not to through-run the busiest stations; it means to turn back closer in on the weaker side and send more trains back where they’re needed sooner.
Is this really an issue? Even on your heavily trafficked mainline you should be using inline turnback stations.
At Shinagawa, outbound Tokaido Line trains use platforms 11 and 12; inbound trains use platforms 6 and 7; and Joban Line trains that don’t go through to the Tokaido Line turn back north using platforms 8-10.
What do you think of trains that feed into a different city’s S-Bahn tunnel takt at each end? I feel like it adds unnecessary complexity to the network, but sometimes the cities are close enough and there’s a significant number of trunk-to-trunk travelers, or the pattern of development is such that there’s no clear border between the two cities’ areas of influence.
Perhaps the most extreme example of “interlining a bunch of S-Bahn lines on a single trunk” is done in Munich where there is very little chance of fitting even more trains on the trunk line, hence the construction of a second trunk…
The more I look at the plans for the Stammstrecke tunnel, the more I get scared, really.
Since the Stammstrecke tunnel has lesser stations, it’s being thought of as an express bypass of the existing tunnel, and so a few express routes are being sent down that tunnel. That means more complicated interlining, but presumably Munich is prepared to handle that.
I certainly wouldn’t call it regional rail, but Muni Metro has those same limits. Everything but item two, really. High throughput in the core is essential. It is double ended, complicating things. But the biggest problem are the delays in various places outside the trunk. It doesn’t take much to see the whole thing collapse, which is why they basically gave up (https://humantransit.org/2020/06/san-francisco-a-forbidden-fantasy-comes-true.html).
Boston also has a highly branched light rail system. I believe that it too has problems with bunching. It definitely looks like a good example of regional rail, with a nice, frequent urban trunk that acts like a Metro.
That being said, I think the frequency on the various branches (in all cases) is better than typical regional rail (often good enough to be treated like a Metro — people don’t bother checking the schedule). So that is more of the general category of “highly branched systems” instead of “highly branched regional rail”.
My guess is there are some systems (especially in the U. S.) which exhibit the same pattern, but without the branching. They simply have turnbacks as ridership drops outside the urban core (outside of the peak period). My guess is that Link, in greater Seattle, will do that. It is hard to imagine running the trains every five minutes in the middle of the day up to Everett — it is too expensive, and there just aren’t enough riders. Yet at the same time, from Northgate (in Seattle) to downtown Seattle, five minutes is basic. Thus I expect half the trains to turn back somewhere. Maybe Northgate, maybe Lynnwood — or maybe both. I could easily see trains running every five minutes in the core, every ten minutes up to Lynnwood, and every twenty minutes to Everett. The savings would be significant, even though that means more switching, and a more complicated servicing system. I remember officials talking about the plethora of turn back options, though — so obviously they are thinking about it years before they actually implement something. There is very little surface running (even in the suburbs) and very few stops outside the core, so I don’t think they would run into that many problems.
There is a problem with only continuing half the trains – on the inbound trip, there will be unequal loading between the trains that continue and those that don’t, leading to bunching.
>> there will be unequal loading
Yeah, but to a very small degree. Less than many branches (where ridership is much higher on one branch versus another). Very few people will ride the trains all the way from Everett to Seattle, especially in the middle of the day. Even many of the Everett riders would get off the train at or before Lynnwood. Most inbound riders south of Lynnwood would have a hard time telling whether the train started out empty in Lynnwood, while the other started out with a handful of riders. I doubt it would lead to bunching especially if the agencies dwell times continue to be pretty large (allowing a lot of cushion).
For what it’s worth: there are short-turns here, e.g. in the off-hours, half of U8s turn at Osloer Strasse. But the short-turn point is always pretty far out, so there’s no real difference in train crowding levels, and it sounds like the same is true of the Seattle system. (In contrast, in New York, the 3 from the north is more or less a short-turn version of the 2 and there is a big difference in peak crowding.)
Yeah, what I’m talking about is an area that is definitely far out. Osloer Strasse is about 5KM from the center of Berlin.
Wittenau station (the far end of the U8) is about 10 KM. Lynnwood — where I would turn back — is 24 KM. Anyway, what I’m suggesting is the plan for the middle of the day, not peak. My guess is trains will go all the way from Everett to Tacoma during peak — a 110 KM trip*. (It would be about 80 KM as the crow flies.)
* Technically, the train won’t go from Everett to Tacoma. It takes too long for one driver. So instead they will pair Tacoma (to the south) with a line to Ballard (to the northwest) and Everett (to the north) with Redmond (to the east).