Which Older Lines Should Express Rail Have Transfers to?

In my writings about metro network design I’ve emphasized the importance of making sure every pair of intersecting lines have a transfer. Moreover, I’ve argued that missed connections often come from having very wide stop spacing, because large metro networks have very closely-spaced lines in the core, and if the stop spacing in the core is too wide, as in Moscow, then lines will frequently cross without transfers. In contrast, in Paris, where the Metro has very closely-spaced stops, there is only one missed connection on the Metro, between Lines 5 and 14. However, what’s missing from this discussion is what to do on lines that, due to network design, have to run express and miss some connections. This question mattered to most RER lines and currently matters to Crossrail and Crossrail 2, and will be critical in any New York regional rail plan.

I claim that the most important connections to prioritize should be to,

  1. The busiest lines.
  2. Lines that are orthogonal to the newly-built express lines.

But before explaining this, I’d like to go over the scale of the underlying problem of prioritizing transfers. For a start, look at the Underground in Central London:

Crossrail is the dashed gray line. Between Paddington and Liverpool Street, it intersects seven north-south lines, including five in rapid succession on the West End; stopping at all of Bond Street, Oxford Circus, Tottenham Court Road, and Holborn would slow down too much what’s intended to be an express relief line to the Central line.

Stopping between two stations and having transfers to both is possible – look at Farringdon-Barbican and at Moorgate-Liverpool Street – but results in very long transfer times. The RER has opted for this solution at Auber, which is located between the Opera and Saint-Lazare, with a transfer stretching over three successive stations on Line 3, leading to legendarily labyrinthine transfers between the RER and the Metro:

Observe that in contrast with the RER A’s convoluted transfer at Auber, the RER B simply expresses between Chatelet-Les Halles and Gare du Nord, missing the connection to the east-west Lines 3, 8, and 9 and the north-south Line 7, and only connecting to the circumferential Line 2 via a long underground passageway. The reason for this is that a transfer station at Bonne Nouvelle or Sentier would be very expensive to construct; the RER’s stations were all extremely costly, and the RER A’s record of $750 million per km for the Nation-Auber segment remains unbroken outside the Anglosphere. On Crossrail (the recordholder in cost per km outside the US, soon to be overtaken by Crossrail 2), it’s the stations that drive up costs as well, and the same problem is even more acute in New York.

The tension is then between the network effects of including more transfer points, and the costs and slowdowns induced by stopping more often. The first point in my claim at the beginning of this post follows immediately: it’s more valuable to stop at transfer points to busier lines. The RER A misses Line 5 entirely, as does the express Line 14, because Line 5 is so weak that it’s not worth it to detour from Gare de Lyon through Bastille to connect to it; the oldest plans for the RER A had a stop at Bastille and not at Gare de Lyon, but under SNCF’s influence the system was redesigned to connect to the train stations better and thus Bastille was replaced.

Whereas the RER A in theory connects to every north-south one except the weakest (although the second strongest after Line 4, Line 13, has an even longer connection than at Chatelet), Crossrail does the opposite. The busiest station in London excluding mainline stations is Oxford Circus, thanks to the three-way transfer of the Bakerloo, Victoria, and Central lines; the Victoria line is the busiest in the system per km (although the longer Northern and Central lines have more riders), and it’s certainly the busiest north-south trunk line. However, plans to have a transfer to both Bond Street and Oxford Circus were rejected in favor of a connection to Bond Street alone. The reason is that London’s low-capacity passageways get congested, and TfL’s hamfisted solution is to omit critical transfers, a decision also made at the Battersea extension of the Northern line, which will miss a connection to the Victoria line at Vauxhall.

This brings me to the second transfer priority: it’s the most important to connect to orthogonal lines. The reason is that parallel lines, especially closely parallel lines, are less likely to generate transfers. New York’s four-track subway lines have very high volumes of local-express transfers, because those are easy cross-platform interchanges; as soon as any walking between platforms is required (for example, on the Lexington Avenue Line at 59th and 86th Streets), transfer volumes fall dramatically. In Paris, transfers between Line 1 and the RER A happen, but usually for longer-distance travel; I find it faster to take Line 1 from Nation to Chatelet than to take the RER A, even without any transfer, purely because it’s easier to get between the street and the Metro platforms at both ends.

This issue was never really in contention when Paris built the original RER system. The one place where the RER prioritized a transfer to a same-direction Metro line over an orthogonal one, Gare du Nord, is such an important destination for commuter and intercity trains that it’s obviously justified to prioritize it over an easier connection to Line 2. However, more recently, the RER E has seen this issue surface with the location of the infill Rosa Parks station. The RER E could have sited a station at the intersection with Line 5, but Line 5 goes northeast and serves much the same area as the RER E, so the network effects from an interchange would be weak. Instead, the station is sited to interchange with the circumferential T3 tramway, which opens up a connection toward Nation and eventually toward Porte d’Asnieres.

In London, the same question is critical to the central route of Crossrail 2. The current plan has three Central London stops: Victoria, Tottenham Court Road (with a transfer to Crossrail), and Euston-St. Pancras. But Victoria itself is not much of a destination, and of the two lines served, the District and the Victoria, the Victoria line is parallel to Crossrail 2 rather than orthogonal to it. The purpose of Crossrail 2 is to add north-south capacity through the West End to decongest the Victoria line and reduce the shuffle at Victoria station between mainline trains and the Underground; to this end, there’s no need to stop at Victoria station itself.

To this effect, Martha Dosztal proposes moving Crossrail 2 to Westminster or possibly Charing Cross. Instead of spending $2 billion on a station at Victoria, London would need to spend probably a comparable amount on a station that interchanges with lines that go northwest-southeast like Jubilee or Bakerloo rather than on the parallel Victoria line; moreover, Westminster and Charing Cross both have connections to the District line, so Crossrail 2 would still connect to all three east-west Underground lines.

Finally, the application to New York is the most delicate. New York’s scores of missed connections come from deliberate indifference on the IND’s part to transfers with the older lines rather than any systematic attempt at prioritizing important interchanges; the older IRT and BMT systems have between them just two missed connections (3/L in Brooklyn, 4-5/R-W in Lower Manhattan). But including better connections in the event the city builds more rail lines remains critical. Second Avenue Subway gets this right by having a cross-platform transfer to the east-west F; there’s no transfer to the north-south Lexington Line, but this is less important given Second Avenue’s role as a Lexington relief line.

Regional rail transfers are especially circumscribed in New York given the system’s nature as a few short tunnels: new tunnels across the Hudson, and ideally a connection between Penn Station and Grand Central. This is why there is little room for improving connectivity between the subway and what I call Lines 1-3 of New York regional rail. However, the priorities I’m advocating in this post suggest two important things about Penn Station: first, it’s important to reopen passageways to Sixth Avenue to allow connections to the NQRW and BDFM trains; and second, it’s not important to have a connection to the 7 at Hudson Yards, as IRUM proposes.

On more speculative lines involving longer tunnels, the same priorities point to my proposed stopping pattern in and around Lower Manhattan. What I call Line 4, a north-south line from Grand Central to Staten Island stopping at Union Square and Fulton Street would intersect the east-west subways: the 7 at Grand Central, the L at Union Square, and PATH and most Brooklyn-bound trains at Fulton Street. The only missed subways – the F/M at Houston Street and the N/Q at Canal – go mostly north-south (except the M, which has a same-platform transfer with the J/Z, connecting at Fulton). Likewise, what I call Line 5, connecting from Pavonia to Atlantic Terminal, would connect to most north-south subways at Fulton Street.

Ideally, it’s better to make every interchange, and subway builders around the world should aim for very long-term planning in order to prevent missed connections in the future. However, when the inevitable changes happen and missed connections are unavoidable, there are emergent rules for which are more important: busier lines are more important than less busy lines, and less obviously, lines that are orthogonal to the new line are more important than ones that are parallel. These priorities make it possible to build express lines that maximize regional connectivity with minimal loss of travel time due to making local stops.


  1. Andrew Thompson

    Crossrail is not a replacement for Central Line, at least not directly. First off its a commuter rail line not a subway and as such has different train lengths and operational criteria. To suggest that you have stations at Bond ST and Oxford St would mean you would effectively have one large station due to the platform lengths. With the short distance between such stations your headway would be increased and likely the ultimate capacity would be reduced. Obviously it would be preferable to have stations at all cross links but its not necessarily feasible from an operational perspective. IN an effort to reduce energy consumption stations are usually at high spots, so that trains decelerate up an incline as they enter the station and then accelerate down a gradient as they leave the station. This cannot always be made to work but its what you aspire too. Closely spacing stations reduces the ability to do this and therefore leads to increase energy usage and heat build up in the tunnels leading to increased ventilation requirements…..etc. and may also impact signal blocks and hence operational headway. Remember also that Cross rail was as much about connecting west to east and providing a connection from Heathrow across to Channel Tunnel Rail Link as much as linking to the existing tube system. Your comments about a hamfisted solution are somewhat unfair as it may have been simple engineering and operational constraints that dictated the solution..

    As for Cross rail 2 I was involved in the late 1980’s on the first version of Channel Tunnel Rail Link which envisaged a line running from Kings Cross down towards Blackfriars and then under the river Thames surfacing at Hither Green. Threading a commuter rail line through the deep foundations, between the existing underground tunnels such as Thames Tideway, the 28ft tunnel being constructed beneath the river, as well as the MoD tunnels and existing tube lines, post office rail tunnels, sewer and water tunnels while maintaining operational grades, signal blocks and being at an elevation that is not so deep that people will be spending 15 minutes to get to the surface is extremely challenging. The optimal solution is becoming increasingly hard to engineer and most solutions are compromises due to engineering challenges that may simply be too expensive to contemplate. It does not help when many of the buildings now have multiple level basements that also get in the way forcing you to follow road alignments which are already congested with underground utilities. Locating station entrances is also increasingly difficult with the congested street scenes that exist in London. All of this will be taken into account as well as the need to relieve the Victoria Line which is hideously over crowded in rush hour. Charing Cross is a nothing Station compared to Victoria which also coincidentally serves Gatwick, Londons second airport. Providing a service that eliminates non at grade transfers for passengers heading to Gatwick from north of London is likely to be one of the aims of Crossrail 2 as well as many other aims. Routing this through Charing Cross would therefore make no sense and may not even be feasible without ultra deep stations whihc would be expensive and unpopular.

    • Alon Levy

      The plan was to have one station with connections to both Bond Street and Ox Circus, on the model used or Moorgate and Liverpool Street or Farringdon and Barbican.

      As for Crossrail 2: Charing Cross is an actual destination, as is Westminster. Victoria is a station where people transfer between mainline services and the Underground. More people get on than off at Victoria in the morning rush hour. And as for “hideously expensive,” TfL estimates the cost of Victoria and Euston-StP at 1.4 billion pounds each. At a tenth that cost I’d recommend looking into large-diameter TBMs to reduce station costs, and pruning everything except the central tunnel segment; replacing the SWML’s four-track berm with a six-track one with retaining walls is bound to be cheaper than the tunnel meandering through the Northern line.

      Finally, I really don’t think it’s true that closely-spaced stations reduce capacity. The capacity on M13 here is 38 tph, with a branch. M14 has some short interstations, flanking the long nonstop segment between Gare de Lyon and Chatelet, and runs 42 tph. In Vancouver, there are some pretty short interstations downtown and the system currently runs 33 tph (with a branch) and is supposed to be capable of 48.

      • Andrew Thompson

        Don’t disagree that Victoria is not a destination. You could attempt to get a station at Westminster but with the Elizabeth Lone there the depth would be problematic. Your comment about large TBM’s reducing station costs is rather naive. At the depths you would be at for some of these locations your going to be out of the London Clay and into the Thanet Sands and Woolwich and Reading Beds which are much more challenging ground conditions to work in. It would be the ancillary services that would be problematic with the ground treatment necessary to manage the ground conditions. Irrespective of the TBM size you need shafts and connecting tunnels, and you would put the station concourse close to the surface anyway so I’m really not sure that large TBM’s are the answer. One aspect that is routinely forgotten about by the champions of such technology is how you install crossovers, switches etc, for operational flexibility within a single tunnel, given grade constraints for heavier and longer trains. There is a reason why this is rarely done.

        As for the Oxford Street/Bond St discussion, have you any idea of what already exists beneath Oxford Circus and just how difficult installing Crossrail would have been. Ideal yes, practical – maybe not.

        • Alon Levy

          Large-diameter TBMs have very easy crossovers and switches, actually: you can put two tracks side by side on one level. Switches are easy as well: you put each track on a different level, and then the tracks can have turnouts without any at-grade conflicts. Barcelona’s L9 uses this technology in part because the crossovers and switches are easier – there’s no need to blast caverns between twin bores.

          The access shafts are an issue either way. Barcelona uses elevators, which are easy to drill because vertical TBMs can be powered by gravity. But in St. Petersburg they used a slant TBM for higher-capacity escalator access at a particularly deep station.

          The rock is a real problem, sure, but it has to be cheaper to blast through more difficult and more heterogeneous rock (more heterogeneous because the tunnel is bigger) than to blow $2 billion on a cavern under Victoria and another $2 billion on a cavern under Euston.

          My understanding is that the reason TfL decided against the Ox Circus connection is capacity on the Victoria line and not the difficulty of building the transfer. Oxford Street isn’t easy to tunnel under, but neither is the London Wall and yet the City station connects to both Moorgate and Liverpool Street.

  2. Eric

    “busier lines are more important than less busy lines”

    Not sure about this. The busier lines are frequently already at capacity, and unable to handle a flood of additional transfer passengers. By putting the transfer on a less busy line, you raise its usage and it becomes a busy line. By putting the transfer on a busy line, you overwhelm it and now have to build a new subway line in parallel to it.

    • Alon Levy

      London sometimes thinks in those terms, hence the lack of a Crossrail transfer to Ox Circus and the under-construction missed connection at Vauxhall. It comes from the “passengers are a burden on our perfect system” school of transit planning.

      What you say about making a less busy line stronger is true only if the reason the line is weak is specifically that it doesn’t have great connections to the rest of the system. For example, the London Overground’s connections with the Underground are horrendous, so it has suppressed demand that new connections could tap into. The same is true of the G, so new tunnels under the East River should try to connect to it (but note that my regional rail plan proposes no such tunnels through Line 6). But M5 is weak because there isn’t all that much demand for north-south travel through Bastille and Austerlitz rather than through Les Halles (i.e. M4 and M7) or the CBD (i.e. M12 and M13). In London, the Charing Cross branch of the Northern line isn’t so busy, since its southern branches have stronger connections to the City than to the West End. In New York, local trains on most lines are weak because they’re slow and people transfer to the express, and historically NYCT even converted 59th Street to an express stop on the 4/5 to facilitate the transfer to the BMT.

      • adirondacker12800

        They went and built the 60th Street Connector and didn’t have to run the GG as an alternate local along Queens Blvd. Now they can run long trains from the Broadway BMT out along Queens Blvd instead of short trains. Buy the cheap real estate, that’s cheap because it doesn’t have service to Manhattan, yer gonna have to change trains. Too bad.

  3. rational plan

    Not sure where youy would fit anymore passemgers onto existing Overground services as they are hideously crowded already. The mahority using it to access the Victoria Line, Jubilee Line and Shordeitch. Going beyond fiver carraiges is going to prove difficult as some of the old stations on the East London Line are vaery old with dangerously narrow platforms that are rather short.

    Plus when they Built the interchange at Canada Water it was for the old tube short tube line so that station is to short for longer trains. Besides the Jubilee is rammed from this point on towards Canary Wharf.

    Heres hoping Crossrail helps a bit but I expect it will fill up again within 5 years.

    • Eric

      I believe no Overground line runs more than 20 trains per hour, and most are much lower. So if the trains are too crowded, they should just run more of them.

        • Eric

          Maybe they can limit the freight to nighttime or something? What system do countries other than the US have for resolving freight/passenger disputes?

          • Alon Levy

            There’s an infrastructure owner that sets charges based on how many paths each train takes. But then deciding what’s a path (i.e. what the reference speed is) is a difficult political question. Is a 100 km/h freight train consuming three paths that could be used by 160 km/h passenger trains, or is a 160 km/h passenger train consuming three paths that could be used by 100 km/h freight trains?

    • Alon Levy

      And yet Crossrail is connecting to the East London Line at Whitechapel… the big miss is ELL/Central line, and that’s a decision made in the 1930s. A connection would presumably allow ELL passengers to transfer to the Central line rather than crowd Shoreditch; the Central line is busier than the ELL and Bethnal Green -> Liverpool Street is reportedly even more crowded in the morning than Victoria -> Green Park, but it runs bigger and more frequent trains than the ELL, so it could potentially take the extra traffic and certainly would be able to if Crossrail existed. Crossrail itself, running even bigger trains than the Tube, should have no problem dealing with ELL interchanges at Whitechapel.

      As for the Victoria/Overground connections, Brixton is a miss (probably a deliberate one to force riders to change at Clapham, except that the only reasonable connections to the West End involve changing again at Stockwell and crowding Victoria anyway); Highbury and Islington isn’t, but the Victoria line’s worst morning crowding is northbound, not southbound.

      • rational plan

        The crossrail interchange at Whitechapel takes care of passengers coming from the ELL from the North, unfortunately does not help passengers from the South as the trains a ultra rammed until Canada water where the most of the passengers disembark west and east on the Jubilee line. There is talk of building a new North South Tunell for the Overground from New Cross Gate to Stratford via Canary Wharf and so allow the Southern trains expand from 5 to 8 carriages and also go direct to Canary Wharf, thereby relieving the Jubilee. But that is a 2040 horizon timeline, so who knows.

  4. Bgriff

    The missing link in this consideration is that sometimes connection stops usefully serve a local market too. In New York in particular, while I agree that a station at 33rd and Madison isn’t a huge priority, it does seem like you could make a case for a third stop somewhere between 125th Street and FiDi. The ideal place is probably somewhere around 55th-59th Street, which does happen to allow a connection to potentially a few crosstown lines, but more importantly is just a useful destination for people on the regional trains to be able to have direct access to without having to transfer to a different line to get there (thus clogging up that other line, and all of the passageways to and from it). It’s vaguely similar to having the N train stop at 49th Street — just because skipping a stop makes the express train go faster doesn’t make it worth it if a lot of people on board that train will have a slower journey because they wanted to get to that bypassed destination.

    Though of course that only works if you’re building a new rail line; if you’re going to use the existing line north out of Grand Central then it’s not really practical to add a stop in that vicinity given the complexity of the tracks there already and the near-impossibility of making modifications to the existing tunnel given how much infrastructure is already built up around it. And the outrageous cost of adding a station in NY is also a problem, though if that can’t be addressed then none of this is going to get built anyway.

    In London, missing Oxford Circus does seem a loss, but almost certainly any solution offering a transfer there would have done it with a single station also connecting to Bond Street, so the Bond Street Crossrail station should be sufficient to serve the local market of Crossrail passengers wanting to get to the general Oxford Circus area. But potential NY plans call for much longer nonstop runs through dense areas.

    • rational plan

      The crossrail stations are double ended, The eastern end of the Bond street station is in hannover square, only a few minutes walk from Oxford Circus. They could have built an underground link easily, but again the other lines are rammed. It might have not been a problem if the crossrail trains did not carry twice as many passengers as the tube trains. The potential for imbalance here was too great.

      • Bgriff

        I am far from an expert on this so I don’t know how to balance the conflicting interests here, but it seems like there will be some number of people starting in Vauxhall and needing to go somewhere on the Elizabeth Line route, who will end up adding crowding to a Jubilee Line train for one stop (as well as adding crowding to the corridors at Green Park) in the name of reducing crowding at Oxford Circus. Making life more difficult for such a passenger seems silly and counterproductive.

        Of course, the planned design does also serve to nudge passengers with choices away from busy Oxford Circus — someone who is starting at Kings Cross and heading to points west on the Elizabeth Line could easily take the subsurface lines over to Paddington or the Northern Line to Tottenham Court Road, with minimal inconvenience to them and with benefits to the overall network. I don’t know how the balance of the two types of passengers works out, though. Since the Victoria line serves a lot of passengers transferring from other services at places like Victoria and Highbury & Islington, perhaps there are indeed more passengers who can simply choose another path of attack toward the Elizabeth Line. (Bakerloo line riders are also victims in all of this, though they do have direct access to the Elizabeth line further west, and most Bakerloo stations south of Oxford Circus offer other direct paths to the Elizabeth Line.)

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