Circles

Rail services can be lines or circles. The vast majority are lines, but circles exist, and in cities that have them they play an important niche. Owing to an overreaction, they are simultaneously overused and underused in different parts of the world. However, that some places overuse circles does not mean that circles are bad, nor does it mean that specific operational problems in certain cities are universal.

In particular, what I think of as the ideal urban rapid transit network should feature circles once the network reaches a certain scale, as in the following diagram that I use as my Patreon avatar:

Circles and circumferentials

Circles are transit lines that run in a loop without having a definitive start or end. Circumferentials are lines that go around city center, connecting different branches without passing through the most congested part of the city. In the ideal diagram above, the purple line is both a circle and a circumferential. However, lines can be one without being the other, and in fact examples of lines that are only one of the two outnumber examples of lines that are both.

For example, here is the Paris Metro:

Paris has a circle consisting of Metro Lines 2 and 6, which are operationally lines; people wishing to travel on the arcs through the meeting points at Nation and Etoile must transfer. Farther out, there is an incomplete circle consisting of Tramway Line 3, where the forced transfer between 3a and 3b is Porte de Vincennes. Even farther out there is an under-construction line not depicted on the map, Line 15 of Grand Paris Express, which has a pinch point at its southeast end rather than continuous circular service. All three systems are great example of circumferential lines with very high ridership that are not operationally circles.

Another rich source of circumferential lines that are not circles is cities near bodies of water. In those cities, a circumferential line is likely to be a semicircle rather than a circle. This is responsible for the current state of the Singapore Circle Line, although in the future it will be closed to form a full circle. The G train in New York is a single-sided circumferential line to the east of Manhattan, not linking with anything to the west of Manhattan because of the combination of wide rivers and the political boundaries between New York and New Jersey.

In the opposite direction – circles that are not circumferentials – there are circular lines that don’t neatly orbit city center. The Yamanote Line in Tokyo is one such example: its eastern end is at city center, so it combines the functions of a north-south radial line with those of a north-south circumferential line connecting secondary centers west of Central Tokyo. London’s Circle Line is no longer operationally a circle but was one for generations, and yet it was never a circumferential – it combined the central legs of two east-west radial mainlines, the Metropolitan and District lines.

We can collect this distinction into a table:

Circle, not circumferential Circumferential, not a circle Circumferential circle
Yamanote Line
Osaka Loop Line
Seoul Metro Line 2
London Circle line (until 2009)
Madrid Metro Line 12
Paris M2/6, T1, T2, T3, future M15
Copenhagen F train
New York G train, proposed Triboro
London Overground services
Chicago proposed Circle Line
Singapore Circle line (today)
Moscow Circle Line, Central Circle
Berlin S41/S42
Beijing Subway Line 2, Line 10
Shanghai Metro Line 4
Madrid Metro Line 6

Operational concerns: the steam era

In the 19th century, it was very common to build circular lines in London. In the steam era, reversing a train’s direction was difficult, so railways preferred to build circles. This was the impetus for joining the Metropolitan and District lines to form the Circle line. Mainline regional rail services often ran in loops as well: these were as a rule never or almost never complete circles, but instead involved trains leaving one London terminus and then looping around to another terminus.

Another city with a legacy inherited from steam-era train operations is Chicago. The Loop was built to easily reverse the direction of trains heading into city center. At the outer ends they would need to reverse direction the traditional way, but there was no shortage of land for yards there, unlike in the Chicago CBD since named after the Loop.

As soon as multiple-unit control was invented in the 1890s, this advantage of circles evaporated. Subsequently rapid transit lines mostly stopped running as circles unless they were circumferential. London’s Central line, originally pitched as two long east-west lines forming a circle, became a single east-west line, on which trains would reverse direction.

Operational concerns: the modern era

Today, it is routine to reverse the direction of a rapid transit train. The vast majority of rapid transit routes run as lines rather than circles.

If anything, there have been complaints that circles are harder to run service on than lines. However, I believe these concerns are all specific to London, which changed its Circle line from a continuous loop to a spiral in 2009. I have heard concerns about the operations of the Ringbahn here, but as far as I can tell the people who express them are doing so in analogy with what happened in London, and are not basing them on the situation on the ground here. Moreover, there are no plans to make the Yamanote Line run as anything other than the continuous loop it is today.

The situation in London is that the Circle line has always shared tracks with both the Metropolitan and District lines. There has always been extensive branching, in which a delay on one train propagates to the entire network formed by these two mainlines. To this day, Transport for London does not expect the lines in the subsurface network to have the same capacity as the isolated deep tube lines: with moving block signaling it expects 32 trains per hour, compared with 36 on isolated lines.

What’s more, the junctions in London are generally flat. Trains running in opposite directions can conflict at such junctions, which makes the schedules more fragile. Until 2009, London ran the Circle line trains every 7 minutes, which was bound to create conflicts with other lines.

The importance of this London-specific background is that the argument against circles is that they make schedules more fragile. If there is no point on the line where trains are regularly taken out of service, then it is hard to recover from timetable slips, and delays compound throughout the day. However, this is relevant mainly in the context of an extensively-branching system like London’s. Berlin has some of that branching as well, but much less so; one of the sources of reverse-branching on the S-Bahn is a line that should get its own cross-city route anyway, and another is a Cold War relic swerving around West Berlin (S8/85).

The benefits of complete circles

The complete circle of the Yamanote Line or the Ringbahn can be compared with incomplete circles, such as the Oedo Line or the various circumferentials in Paris. From passengers’ perspective, it’s better to have a complete circle, because then they can undertake more trips.

Circumferential lines broadly have two purposes:

  1. They offer service on strong corridors that are orthogonal to the direction of city center, such as the various boulevards hosting the M2/6 ring as well as the Boulevards des Maréchaux hosting T3.
  2. They offer connections between two radial lines that may not connect in city center, or may connect so far from the route of the circumferential that transferring via the circumferential is faster.

Both purposes are enhanced when the route is continuous. In the case of Paris, a north-south trip east of Nation is difficult to undertake, as it requires a transfer at Porte de Vincennes. Passengers connecting from just south, on M8 or even on M7, may not save as much time traveling to lines just north, such as M9 or M3, and might end up transferring at the more central stations of Republique or Opera, adding to congestion there.

In contrast, in Berlin the continuous nature of the Ring makes trips across the main transfer points more feasible. Just today I traveled from my new apartment to a gaming event on the Ringbahn across Ostkreuz. At Ostkreuz the trains dwelled longer than the usual, perhaps 2 minutes rather than the usual 30 seconds, which I imagine is a way to keep the schedule. That delay was, all things considered, minor. Had I had to transfer to a new train, I would have almost certainly taken a different combination of trains altogether; the extra waiting time adds up.

Why are circles so uncommon?

The operational concerns of London aside, it’s still uncommon to see complete circles on rapid transit networks. They are the ideal for cities that grow beyond the scale of three or four radial trunks, but there are only a handful of examples. Why is that?

The answer is always some sort of special local concern. If city center is offset to one side of the built-up area, such as in a coastal city, then circumferential lines will be semicircles and not full circles. If there is some dominant transfer point that requires a pinch, then cities prefer to build a pinch into the system, as is the case for Porte de Vincennes on T3 or for some of the lines cobbled together to form the London Overground.

This is similar to the question of missed connections. Public transportation networks must work hard to ensure that whenever two lines meet, they will have a transfer. Nonetheless, missed connections exist in virtually all large rapid transit networks. Some of those are a matter of pure incompetence, but in many, rail networks that developed over generations may end up having one subway line that happens to intersect another far from any station on the older line, and there is little that can be done.

Likewise, it is useful to ensure that circumferential lines be complete circles whenever the city is symmetric enough to warrant circles. Paris, like other big cities with strong transit networks, is good but not perfect, and it is important to call it on the mistakes it makes, in this case building M15 to have a jughandle rather than running as a complete circle.

60 comments

    • Mikel

      It is indeed bizarre and a consequence of the kinda developement-oriented transit that characterizes the Madrid Metro extensions of the late 90’s and early 00’s: the regional government built new lines with the aim of using trains as a trawling net for suburban votes. But they didn’t bother coordinating with municipal planners, so the result is circuitous alignments that go through car-dependent blight. See for example Las Tablas station on Line 10:
      https://www.google.com/maps/@40.508553,-3.6697643,3a,60y,357.95h,93.58t/data=!3m6!1e1!3m4!1sq90vjGycCfP5fMutaL5KNw!2e0!7i16384!8i8192!5m1!1e2

      Or Las Suertes station on Line 1:
      https://www.google.com/maps/@40.3635126,-3.5992892,3a,60y,189.95h,88.86t/data=!3m6!1e1!3m4!1sIMdSLiOITIVehnGOsqtH1w!2e0!7i16384!8i8192!5m1!1e2

      The reason for Line 12 was, as far as I know, the lack of good connections between the mostly working-class towns south of the city of Madrid. Cercanías line C-5 connects Móstoles with Alcorcón and Leganés with Fuenlabrada, but the network is radial. Since the then-(and still-) governing PP despises surface transit, they built a single zig-zagging, 40 km metro line connecting both the historic cores of the towns and also most of their newly-developed areas.

      The result is a mixed bag. The stations are modern and fully accessible, average speed is good, and each town centre has a good connection between this circunferential metro and its radial Cercanías line (see for example Getafe Central: https://upload.wikimedia.org/wikipedia/commons/1/1e/Getafe_Central_interior.JPG).

      On the other hand, constructions was somewhat shoddy (half of the line was closed for reconstruction last year: https://elpais.com/ccaa/2018/10/13/madrid/1539455788_793698.html), and Metro and Cercanías are still not fare-integrated (nor will be in the foreseeable future), which makes the line less atractive than buses for poor people who commute to Madrid, even more so since the latter is in a perpetual state of meltdown. This results in poor ridership: 857K yearly passengers per km, while the circular Line 6 has 4.4M / km·year and Zaragoza’s surface tram line gets 2,2M / km·year.

      TL;DR: political incentives during a housing bubble led to prioritizing coverage of in-development areas rather than providing actually useful service.

      • Herbert

        Is there any connectionthis construction and the more revealed corruption of the Madrid local government during that era?

        • Mikel

          Indeed, some metro extensions suffered suspicios cost increases after changes were made to the originally awarded contracts:
          https://elpais.com/ccaa/2018/09/29/madrid/1538217497_088808.html
          This appears to be part of the “Púnica” corruption network and involves Francisco Granados, a powerful regional minister until 2011. Not to be confused with the M-30 freeway tunnel’s cost overruns, which were result of incompetence and/or malice by an entirely different administration, the City of Madrid.

          As Alon often points out*, Spanish contracting procedures are often robust and transparent enough, but each administration has different standards – see for example the L9 clusterfuck in Barcelona, created by the also very corrupt Catalan government of the 00’s.

          I wouldn’t be entirely surpirsed if there were instances of corruption regarding urban development along Madrid’s L12, though. Rezoning of the land alog the line’s ROW must have been a magnet for pay-to-play schemes between avid developers and local councillors. Anyway, the bubble burst 10 years ago and to this day there are several phantom stations, buried in the middle of nowhere and awaiting residential development that may never come… while perhaps not corruption, it might be classified as excessively optimistic overbuilding.

          *In Spain we have a common belief that our government (at all levels – national, regional, municipal) is pretty opaque and incompetent when it comes to building infrastructure. After reading Alon’s reporting on other developed countries (esp. the US), it turns out our system is… mostly fine? Still lots to improve, I think.

          • Herbert

            Spain has lots and lots of problems. Most of them related to never really having an honest accounting about the Franco era.

          • Mikel

            It would be interesting to know how metro construction costs were like in Francoist Spain. I honestly have no idea wheter they were similar to modern-day autocracies or to 1960s Italy. I wonder if Alon has any data on this?

          • Mikel

            There were some expansions in Barcelona, mainly the lines now numbered L5 and L7. Aso in Madrid – construction on Line 6 begn in 1969, but wasn’t originally planned as a full circle IIRC.

            Sevilla’s metro was planned in the 1960s, but wasn’t built until later.

            P.S. I just found some data on construction costs:
            http://hemeroteca.lavanguardia.com/preview/1966/08/18/pagina-19/32657774/pdf.html?search=L%C3%ADnea%20IV%20metropolitano

            The Sagrera-Sants portion of what today is L5 is quoted as bugeted at 942M pesetas in 1966 money; 197M for the L3 extension from Liceu to Poble Sec. I have no idea how to convert that to 2019 euros, though.

    • Eric

      It’s a feeder line for the various other lines it intersects. No stop on M12 is more than 4 stops from a transfer with M10 or suburban rail. A similar “people mover” type feeder line exists in Singapore; there may be others elsewhere. At Spanish construction costs, it’s probably worth it.

  1. Michael James

    As I understood it, the incomplete circles in Paris are very deliberate. Well, obviously the M2 + M6 is deliberate but I remember reading that there is an engineering reason to break T3a/T3b, essentially so that any problem on one won’t stop the entire service? It seems that M15 is being very deliberately created with that oddball break. Again, Alon, your rationale seems ok in the abstract but surely those responsible for planning RATP have some good reasons (other than not having the luxury of easy crayon on paper)?

    As usual I don’t reckon London has many “good” lessons to teach, mostly because it was never designed as a network but grew as a patchwork of competing lines that eventually were forced into a single network–more or less but so clearly imperfectly. Of course Anglophiles will boast that the LU proves there is no point to central planning while actually it is the opposite. Though, when you learn of its history it is remarkable it functions as well as it does. The long waits caused by the lack of separation of Central/Metropolitan/District is infuriating and utterly inexplicable except in the context of stubborn lack of planning (predicated on austerity for public spending).

    FWIW, further expanding on your thoughts about why circles rarely get built I would add that if they aren’t planned from the beginning, they become increasingly difficult due to politics (NIMBYism), cost (forced underground) and beancounterism (won’t they mostly run at lower pax per km than a radial or a central line? and thus be harder to justify?). On these bases presumably they are going to be more common in authoritarian places like Moscow and China (and Singapore?).

    • Eric

      ” essentially so that any problem on one won’t stop the entire service”

      All you need is a couple track switches along the way, and a break won’t stop service, you can just reverse at the switch.

      I would more think the issue is unreliable headways over a very long route. Or possibly wasted resources if the ideal headways on the two halves are too different.

      • Henry

        It’s also worth noting that Line 15 is much longer than other circle lines.

        Beijing Line 2 is 23 km. London Circle Line is 27 km. Yamanote Line is 34.5 km. Moscow Central Circle is 54 km. Paris Line 15 will be a whopping 75 km.

        • Michael James

          That’s because M15 is ring #3, after #1 M2/M6 (26 km) and #2 T3a/T3b (≈41 km operational; gap ≈10km remains).
          It can be justified because it runs thru the Petite Couronne which remains quite dense at about 7,000 residents/km2 (about 5m residents not including the 2m+ of inner Paris; approx. 15km radius). Though it won’t be able to match inner-Paris lines, at least on pax per km, the density should support reasonable traffic especially as part of Metropole Grand Paris its centres will be nurtured, ie. will grow. And perhaps just as relevant it will take some pressure off Metro lines inside Paris which are approaching saturation. The overall plan supports the attempt to get more people out of their cars–which means those in the near-banlieus of Petite Couronne. Of course it is the zone in which most “Parisians” (or more correct, Franciliens) live.

        • Eric

          I expect the number of stops is a better measure than the length in km. Line 15 is longer, but its loop has only 36 stations (for comparison, Beijing Line 10 has 45 stations).

          • Michael James

            I would dare to suggest that Beijing-10 may be a design that might be regretted, with such a length (57km) and so many stations that its inter-station distance is only 1.2km. It is currently the world’s longest subway loop line.
            Paris-M15 has 2.1km between stations so on average (other things being equal) you will get to your destination at close to half the time.

          • Michael James

            Alon Levy, 2019/05/27 – 08:31
            Seoul’s Line 2 has a 48 km main loop and is very busy.

            Any of these metros in these mega-cities is going to be busy. Efficiency is the more important question. Seoul-L2 has a 1.18km inter-station distance. However I don’t know how far out it is, so this density might be justified–but that convenience will be paid for by slow service.
            Surely you agree that such a short inter-station spacing on the 75km M15 would not be a great idea? Unless the idea is that most users will be joining it from one of the major radials and only travelling a few stops? That’s not what either Seoul-L2 or Beijing-10 look like but I guess it is a feasible majority use of Paris-M15.

          • Alon Levy

            Seoul’s Line 2 is not circumferential – it’s rather like the Yamanote Line but bigger, with one end of the circle lying in the primary CBD and the opposite end in a huge secondary CBD (Gangnam in Seoul, Shinjuku in Tokyo).

            On M15 I would not prescribe 1.2 km interstations. I’m genuinely not sure what’s optimal for it given expected ridership patterns, but it probably should be wider.

          • Michael James

            Alon Levy, 2019/05/27 – 09:40
            Seoul’s Line 2 is not circumferential

            Yep, that makes sense, even though it is known as the Circle Line, so it’s justified.

      • Michael James

        I suspect it might be simpler. These are surface tramways so are susceptible to traffic snarls such as caused by accidents. Even though T3a/T3b are partly on their own ROW, they have to cross about 30+ main arterials that connect inner Paris to outer-Paris across the Periherique (and are also feeders for the Peripherique).

  2. yuuka

    It’s interesting to note that JR East can operationally isolate the Yamanote Line into inner and outer loops – each with their own platforms at every station, and extra terminal/overtaking tracks at Ikebukuro and Osaki which are near the depots. Apparently this can prevent minor delays from affecting both directions of service.

    At least according to this NHK video. https://www3.nhk.or.jp/nhkworld/en/ondemand/video/2049065/

  3. Matthew Hutton

    The other point about the London circle is that not many journeys are affected negatively by having to change trains at Edgware Road, as at Paddington you can access both branches anyway. With a train only every 7 minutes on the circle line using the radials was probably quicker for most journeys. Especially as Regent’s Park and Great Portland Street are close, and so is Bayswater and Queensway.

    • Alon Levy

      Yeah, the interlining gets to the point that one blog plausibly suggested breaking the circle entirely by extending the Met east under the Thames to take over the Greenwich line and North Kent to Abbey Wood.

  4. Eric

    The big question which you do not address is, why have a circle line at all?

    To this I would say that transportation networks can take the form of a grid (which spreads the load evenly across parallel lines, and has logical and convenient access from anywhere to anywhere) or a radial system (which effectively serves a single “downtown” effectively). However, even a radial system must provide for a lower level of trips in all directions away from downtown. This means either a grid with radial lines imposed, or a polar graph with concentric circles (which forms a rough grid on a local scale when you get far from the center). The grid with radial lines is pretty common where the grid is roads and the radial lines rapid transit (i.e. Chicago, Melbourne); Beijing and southern Seoul have grid-line tendencies in their rapid transit. As for the polar graph, there you can actually have logical circular lines. Moscow is the best example of this – it has two complete circular lines (5, 14) and three incomplete ones (11, 11A, 13) which, together with the radial lines, form a polar layout in the suburbs.

    • Alon Levy

      Beijing has a gridded street network, and a lot of parallel lines on its subway, but there’s still a much denser spacing of lines that pass through the cores than of lines that do not. Even Mexico City has a clearly-defined city center in its metro network, and the three radials are by a big margin the busiest lines in its system.

      I don’t want to reopen the street vs. road distinction tooooo much, but to the extent it exists, Beijing’s road network is radial-circumferential, with the ring road system. It’s just overlain on a street grid.

      • Eric

        I don’t think Beijing really has a significantly denser network at the core. At least until you get to about 15km from the center, where the grid roughly ends.

        I can’t speak to the ridership of the different lines though.

      • bahntemps

        The proximate reason that Beijing’s Line 2 is a circle is because it was built under the city’s inner city wall and moat. The wall was dismantled after the revolution and was replaced with the 2nd Ring Road–the first “ring road” is formed by a grid of streets immediately beyond the walls of the Forbidden City–and Line 2. That’s why a lot of Line 2 station names end in “men” (gate 门).

        I’m sure there are more practical reasons, but the given reason for Beijing’s strict(-ish) street grid is fungshui. Whatever the actual reason, the grid has been there for a very long time. Main streets are wide, straight and regular: There’s a very, very old idiom that, due to the street grid, Beijingren always know which way’s north. Those gridded streets resulted in regularly-placed gates, which became stations in the 1980s.

        Commercial activity was always centered on the city gates (which were massive!) so it was relatively easy to replace the gates with ring road interchanges and subway stations. That remained the case in the ’80s and ’90s, when all foreigners, and the commerce associated with them, were confined to the area between the second and third ring roads east of the city, and specifically on the streets radiating from Chaoyangmen and Fuxingmen.

        • Alon Levy

          I did not know about the special zone for foreigners in the 1980s and 90s! That explains a lot about Line 10 specifically and the new CBD on the Third Ring Road…

          The old wall issue also exists in Paris. In Berlin there was a wall for tax collection of similar age, but there’s no circular U-Bahn line along its route; U1 traces its southern portion and the M10 tram traces its northern portion.

          • Herbert

            Tax collecting walls were very common in German cities.

            The train station is often just outside said wall

    • RossB

      Jarrett Walker spends a fair amount of time writing about the advantages of grids (https://humantransit.org/2010/02/the-power-and-pleasure-of-grids.html). Very few subway systems were designed that way. Like a small city bus network, they were usually designed first at getting people to downtown along major corridors (a radial network). But unlike a bus network, each time they went downtown, they detoured a bit, to get better coverage (radial bus networks tend to converge). Even the relatively recent DC Metro is built that way. As line after line is built, it becomes impossible to transition to a grid (unlike with a bus network, where change is easy). This is where a circle seems most likely — as part of the evolution of a radial system. That would make it similar to Walker’s last diagram (what he calls a spiderweb). Unlike many cities, DC is well suited for it. Yet it doesn’t exist yet in part because of the good coverage downtown. It is telling that the primary advantage (in my opinion) of the proposed downtown loop is that it covers places like Georgetown, which should have been covered before. There has been talk about a beltway loop, but it would be largely connecting suburban areas that don’t have that much everywhere-to-everywhere demand. My guess is that we don’t see that many circles because they are likely to evolve only in mega-cities (like Tokyo) where there is huge population density several miles out from the core.

      • Eric

        Very few metro areas have the population and density to support a grid of subway lines. But like Chicago and Melbourne, they still have a grid for lower-density forms of transportation (cars, buses, mixed traffic trams).

        The “spiderweb” is what I called a polar graph.

        I suppose Beijing and Seoul, with their subway grids, are unusual because they developed massive areas of massive density and only then started building subways in a serious way.

        Note that London’s West End has something arguably better than a rectangular grid – a triangular grid! (Imagine equilateral triangles tiled to cover a surface) Triangular grids cannot work for surface streets because there would be too many conflicting movements at the intersection. But for subways where transfers are done by alighting and walking, this is not an obstacle.

    • Herbert

      One historic origin of circle lines (certainly the Berlin Ringbahn) is linking historic terminus stations. The benefits of a circle in that case should be obvious.

      Many cities also have circular railways that mostly serve as freight bypasses. Berlin has one of those, but so do or did Nuremberg, Leipzig and plenty of other cities. For the most part those freight circles see little or no passenger traffic

      • Michael James

        That exactly describes Paris’ Petite Ceinture which was built in 1844 to link all the mainline rail stations so as to transport building materials for the construction of the Theirs Wall (upon which today’s Peripherique ring-road is built; similar to the way M2 & M6 were built on the older Fermiers Generaux wall). It was a trenched railway and was rather extravagant in that it had a limited use; a prime example of justification on the basis of “national security” (plus ça change … ). But then there is “re-purposing” which is what happened in 1854 when parts of it were converted to a passenger railway beginning with the Auteuil line out of St Lazare. At its peak (IIRC the 1900 exposition) it carried 30m pax, but it persisted until 1934; however I recently discovered this amazing factlet: “… except the ligne d’Auteuil, which remained open until January 1985.” Which means it was still running when I lived in Paris; can this be true and was it still using steam locomotives? Seems unlikely though the line remained usable and perhaps was a service line for SNCF? In 1988 the Auteuil line was incorporated into the northern branch of RER-C with its diagonal bridge across the Seine/Iles des Cygnes.

        Given that the PC had its own ROW including bridges across the Seine, and access to all mainline stations, it is a bit of a mystery to me why it wasn’t upgraded to modern metro/lightrail. It was closed as uneconomic and replaced by buses on the Boulevards Maréchaux. I guess it didn’t have any direct pax links to the Metro. About 80 years later they kind of replaced its function with T3 but of course, like the buses, runs at grade.

        Sorry, rambled a bit. My point was that even when the most expensive and difficult part of the infrastructure was in place, a circle line fell into disuse.

        • Herbert

          Yeah, but bits and pieces of it were already built by the Nazis. Same with the A10 highway.

  5. adirondacker12800

    The G train in New York is a single-sided circumferential line to the east of Manhattan, not linking with anything to the west of Manhattan because of the combination of wide rivers and the political boundaries between New York and New Jersey.

    It was to provide local service on the Queens Blvd line and what we now call the Culver line. It was never meant to have anything to do with Manhattan other than to provide local service in Brooklyn and Queens for the expresses to and from Manhattan. Including the ones that were going to be running on Second Avenue someday. There’s a reason Hoyt-Schemerhorn has four islands and six tracks. Take your pick for whatever that reason might be.

    http://www.thejoekorner.com/indsecondsystem/index.htm

    • Alon Levy

      It was meant to connect Downtown Brooklyn and Long Island City without going through Manhattan; the local tails on the South Brooklyn and QB Lines were planned separately.

      • adirondacker12800

        The flying junctions in the vicinity of Queens Plaza or Hoyt-Schemerhorn were an accident?

  6. df1982

    So is it not worth also distinguishing in your table between self-contained circles (Moscow, Glasgow subway), and circle lines with linear branches diverging from them (pre-2009 London, Berlin)? The former seem to function reasonably well, but it’s the latter that have massive problems with reliability and headway management. The Ringbahn has much more uneven headways than the Stadtbahn, for instance, and worse reliability.

    Jarrett Walker also makes the point that, beyond a certain arc, circle lines fail to provide anyone with a direct trip, and thus generally discourages them in transit usage, although he does make an exception for orbital lines. The Yamanote line may work well, but it’s not a design you would seek to replicate if working from a blank slate.

    • Alon Levy

      Yeah, so Jarrett is operating in a context of small-city or suburban bus networks, in which you indeed don’t want to run things in circles. It’s very different for rapid transit, because a) frequencies are high enough that the spoke-circle-spoke three-seat ride may well work better than the spoke-spoke two-seat ride, and b) you really need a radial network but also service in multiple directions within the city. Here in Neukölln, the U-Bahn provides north-south service as well as service toward Charlottenburg, but going northeast I take the Ringbahn. At Nation I would routinely take M2 and M6, and judging by overall ridership volumes on these lines, I was not alone.

      I actually would replicate a lot of circles from a blank slate, like the Moscow circles or the ones in Paris, the latter tidied up to be closed circles. Yamanote I don’t know if anyone takes between the western and eastern legs, e.g. Shibuya-Tokyo or Ikebukuro-Tokyo. Were I to redesign Tokyo’s rail network from scratch I’d probably do neater concentric circles, e.g. Ikebukuro-Shinjuku-Shibuya-Shinagawa-Toyoko-Asakusa-Ueno-Ikebukuro and then something farther out instead of Oedo, but I get why Tokyo looks the way it does.

      • yuuka

        “Yamanote I don’t know if anyone takes between the western and eastern legs, e.g. Shibuya-Tokyo or Ikebukuro-Tokyo”

        For such trips people tend to take the subway, or if you have a JR Pass and want to stay within the JR network, the Chuo Line.

        Although I seem to recall there’s actually a plan to build a transit line along Kannana-dori and Kanpachi-dori streets, which lie somewhere between the Yamanote and Musashino lines. However, all the sources I remember seeing are in Japanese…

      • Si Hollett

        When the London Overground was created and the tube-fan community were all talking up “Orbirail” as if it would be some big game changer to travelling via zone 1, Max Roberts (of mapping fame) wanted to put it to the test, with me and another person racing him between two sets of stations. Max (very unlike him as he doesn’t like the deep tube much) took the radials, I took orbitals, and the other took a third route.

        Orbital routes only beat one radials route and that was Highbury and Islington to Canning Town via Stratford (due to me cheating and running through Stratford to just catch my Jubilee line train) beat via Green Park by about 4 minutes, and via Moorgate and Bank by about 2 minutes (via London Bridge would have been quicker, but the end destination was City Airport and I got on the other person’s DLR train) – basically all three routes were basically very similar in time, as one would expect for something of that angle.

        OK, there were some issues with orbital frequency, but when we factored that in by removing wait time the pi radians rule held up well.

  7. df1982

    I have no problem with circumferential circles, it’s the non-circumferential ones that I don’t think are worth replicating. Unless you have Japanese/Swiss style efficiency you either have reliability problems or have to build a lot of fat into the timetable (which would otherwise be dealt with at the terminus station), they end up taking indirect routes for a lot of journeys, and they can be difficult for passengers to navigate. I think it’s indicative that most well-functioning modern metro systems avoid circle lines apart from the very particular usage of circumferentials (and, as you note, even there they often break them up).

  8. Lauri Kangas

    Does extending the reach of (feeding) heavy rail fall under one of the two main purposes? While feeder lines could have any shape and length, some (surface) circle / circumferential / orbital lines certainly serve this purpose alongside longer trips. Berlin M10 and Stockholm’s Tvärbanan at least.

    • Alon Levy

      I feel a bit weird about calling M10 circumferential (it serves Hauptbahnhof!), but I can see it as one, sure. Both it and Tvärbanan provide extra service in the orthogonal direction to the radial one, i.e. providing east-west service around Gullmarsplan, north-south service around Liljeholmen, east-west service on Bernauer, north-south service on Warschauer, etc. I guess the feeder aspect comes from the fact that if you live (say) between Liljeholmen and Gullmarsplan you’re still probably traveling to T-Centralen or Slussen rather than to Alvik, so Tvärbanan just feeds the T-bana.

      • lcpitkan

        Or if you live in Hammarby Sjöstad you are quite likely to use Tvärbanan to connect with the T-bana at Gullmarsplan. But there is a conflict of interest between serving radial-to-radial and serving as a feeder, because the optimal stop spacing is different. Like any line passing through a city/local centre really.
        I guess for M10 I still think in terms of ending at Nordbahnhof. But we could substitute M13.

      • J.C. Penn

        The M10 is definitely circumferential. Berlin’s main centre is along the axis from Alexanderplatz to Potsdamer Platz. The M10 forms an almost perfect semi-circle centered on Alexanderplatz from Warschauer Straße to Nordbahnhof with an extension to Hauptbahnhof. In addition the M10 runs roughly parallel to the Ringbahn for most of its time.

        This also doesn’t change if you look only at the structure of the transit network. Berlin’s Hauptbahnhof is its “main station”, but not its central station. The Stadtbahn and the North–South S-Bahn meet at Friedrichstraße station, not at Hauptbahnhof. The Hauptbahnhof is only at the fringes of Berlin’s central area. The other candidate for a “Berlin central station” would be Alexanderplatz, the former centre of East Berlin.

  9. Si Hollett

    The Met and the District really really didn’t want to build the Circle line (the Aldgate bit). And turning steam trains wasn’t the driver of that (nor, AFAICS, things like the South London loop services, the Middle, Outer and Super Outer Circles which all had two termini), with both companies happy with their termini arrangement that meant they could fuel and water locos in the space that their termini provided, rather than as a pit stop in a confined space (which caused issues in the early days of the Circle line service). They were forced to build it, and run services on it, by Parliament (and it took the bribery of granting extensions to Whitechapel and a lot of cajoling to get it built).

    That it was never served well (now 6tph, 7tph peak/7.5tph off-peak before the rejig) and that has always been adequate (unlike the similar frequency Aldgate East – Liverpool Street), show that it was never a useful link for passengers (putting aside the separate operational issues that plagued it). It’s not worth getting rid of now it exists, but I doubt it would have passed a business case, even with the, current, nearly 150 years of use factored in, and not factoring the opportunity cost of not having two SSL routes east of Aldgate…

    The LPTB, created in 1933, very quickly and successfully pushed for the removal of the legal requirement of running Circle line trains, but the Circle (as a continuous loop, as required by the repealed part of the legislation about it) was the service all the way until 2009 as it took an age for them to work out how to do it in a way that worked.

    And T-Cupping didn’t necessarily demand the change at Edgware Road – a desire to serve Hammersmith better did (the Circle could have run Wimbledon – Edgware Road – Kings Cross – Aldgate – Victoria – Edgware Road instead).

  10. Henry

    So from what I can understand of this video in French (https://www.youtube.com/watch?v=6QI3bx_5eNw), Paris M15 might not be operated as a spiral after all.

    There are two plans under consideration.
    – 100% of trains run as the spiral pinched at Champigny Centre as a terminal
    – 50% of trains run the spiral, and 50% run M15 as a loop, so you don’t need to change trains at Champigny Centre if you board the correct train

    • Michael James

      What is the logic of running that Champigny-Centre to Noisy bit? I’ve never read any explanation.. I suppose it links the termini of M11 (extension) and M16, but why not extend M16 for that bit, and keep the loop intact? I suppose the direct connection to RER-A at Noisy is a priority?

        • Michael James

          Surely not? None of the existing Metro has storage lines on their operational bits. Having the link, ok, but I don’t accept that that is the real reason. It seems that the RER-A station already there has been a target for the termini of all these new lines and extensions (M15, M11, M16) for a long time. Anyway, as I said, it is not clear if the final form of the circle line is set in stone; the bit of crayon connecting Champigny-Centre to Rosny-Bois-Perrier is tentative on some maps I’ve seen. One could also see that the bit from Noisy to Rosny-Bois-Perrier, currently crayoned as M11-extension, could become M16’s return route to the circle?
          I reckon it might be too early to obsess much over this stuff and we’ll have to see it evolve over the next 5 years or longer.

          Incidentally, I’m losing the war, but I object to people posting links to YouTube videos as part of “evidence” or an argument. Anything that is serious, or to be taken seriously, needs to be clearly elucidated in print somewhere. FWIW, I never click on such links (not least because the signal-to-noise (ie. information-to-fluff) on those things is usually abominable, plus the experience equally awful).

          • Henry

            FWIW, the videos are primary source media releases describing public outreach meetings.

            PDFs come with their own pitfalls; they’re not easily searchable (and thus out of the reach of search engines like Google), can have issues with text formatting (so copy-pasting into translation services is not an option), and on top of that they’re not usually accessible. And I’ve yet to see a agency bother writing it all out on a pure web page.

        • Michael James

          Henry, 2019/05/28 – 14:49
          And I’ve yet to see a agency bother writing it all out on a pure web page.

          Yeah, but it isn’t any justification or even rationalisation.
          Here, when the conservatives gained power they immediately went to war against our ABC (Australian Broadcasting Commission) by the tools available: appointed a ex-Murdoch flak as the new CEO (without any media experience, she was a marketer! welcome to the modern world) and by cutting budgets (total cuts about $450m to date, another $84m in the pipeline).
          Anyway, one of her first budgetary actions was to cut “transcription services”, which was responsible for turning into words in documents much of the voice-broadcast material. Obvious why politicians especially of the Right (though the Left usually have arguments too) hate having such a record: truly “on the record” and searchable (one can search PDFs but not recordings), and from the ABC where all politicians have innumerable interviews on serious stuff (that doesn’t ever happen on the commercial broadcasters). The PBS-Newshour still produces transcripts of their interviews and investigative pieces. And of course in any legalistic situation, like boardroom meetings, courtrooms and Hansard, a transcript is always produced and placed on the record.

          And can we really trust any of those videos? Look at the current fuss about the “drunken” Nancy Pelosi!

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