Overnight Public Transit

American cities try to aim for 24/7 rail service, imitating New York. European cities except Copenhagen do not, and instead have night bus networks. Both of these options have fascinated various transit reformers, but unfortunately sometimes the reformers propose the wrong option for the specific city. This post is intended to be a set of guidelines for night buses and the possibility of 24/7 urban rail.

Maintenance windows

The reason rail service does not run 24/7 is maintenance. Tracks require regular inspections and work, which are done in multi-hour windows. Over the last century or so, the big urban rail systems of the world have standardized on doing this maintenance at night. For example, in Paris there are about 4.5-5 hours every weeknight between the last train of the night and the first train of the morning, and one hour less every weekend night. In Berlin trains run all night on weekends and have 3.5-hour windows of closure on weeknights.

The regular windows may be supplemented by long-term closures, during which passengers are told to use alternatives. Berlin occasionally closes some S-Bahn segments for a few days, and (I believe much more rarely) U-Bahn segments. Paris does so very rarely, usually for an entire summer month during which many Parisians are away on vacation and systemwide ridership is lower, and usually when there are easy alternatives, such as the RER A and Metro Line 1 substituting for each other.

The English-speaking world tends to have extensive weekend shutdowns for maintenance. London has them quite often in addition to nighttime shutdowns. New York runs trains 24/7, using the express tracks on most of its trunk lines to provide service even when the local stations on some segment are closed for maintenance. As American cities have mostly copied New York, they do not know how to wrap up maintenance during their usual nighttime windows and seek weekend closures or shorter hours as well. Thus, for example, BART has claimed that it needs 7-hour windows during weekend nights, citing the example of Paris, whose weekend night closures actually last less than 4 hours.

Flagging

I know of one city that runs its subway 24/7 without interruptions: Copenhagen. Overnight, Copenhagen single-tracks around worksites – frequency is low enough that trains can be scheduled not to conflict. As the trains are driverless, wrong-way running is quite easy. Moreover, there is ample separation between the tracks thanks to the Copenhagen Metro’s twin bore construction; thus, trains do not need to slow down next to worksites, nor must work slow down when a train runs on an adjacent track.

In New York, tracks on each line are right next to each other, with little separation between them. Thus, there are rules that are collectively called flagging under which trains must slow down to a crawl (I believe 10 miles per hour, or 16 km/h) when next to a worksite, while work must pause next to a moving train. The flagging rules apply even when there is more substantial separation between adjacent tracks, such as columns and retaining walls, provided there is any opening allowing passage between the tracks. The safety margins have been made more generous over the last 20 years, which is part of the reasons trains have slowed down, as reported separately by myself, Dan Rivoli, and Aaron Gordon. At the other end, maintenance costs in New York are very high thanks to the constant interruptions.

If it is possible to single-track at night without onerous flagging rules, then cities should go in that direction, using automated rail signaling such as CBTC, even stopping short of driverless trains. In cities with twin-bored tunnels this works provided there are regularly-spaced crossovers between tracks in opposite directions. London is generally poor in such crossovers, and installing new ones may be prohibitively expensive if blasting new connections between tunnels is required. In contrast, on Line 14 in Paris, there are almost sufficient crossovers – the longest stretch is between Bibliotheque and Madelaine, at 14 minutes one-way, and single-direction switches exist at Chatelet and Gare de Lyon, just one of which needs to upgraded to a full diamond crossover. There, 24/7 operation is plausible, though perhaps not so useful as the rest of the system is not 24/7.

Even some cut-and-cover metros can have sufficient separation between tracks for nighttime single-tracking. In Berlin the distance is adequate, at least for some stretches – the tracks are not right next to each other. Even in New York, there are segments where it is feasible to construct partitions between tracks, provided the agency changes flagging rules to permit regular operations and maintenance on adjacent tracks if a partition has been constructed. The cut-and-cover nature of these systems should facilitate this pattern since the cost of building the required crossovers is not prohibitive, just high.

Night buses

Night buses are attractive for a number of reasons. The most important is that in the after hours there is so little surface traffic that buses can match the speed of rapid transit. Moreover, ridership is usually low enough that a bus has adequate capacity. Finally, surface transit can make small detours, for example to reach a common timed transfer, since transit is dependent on both scale and mode. During the day Vancouver has a bus grid, with most buses arriving every 8-10 minutes, but at night it has a half-hourly radial network with a timed transfer, and little relationship with the shape of the SkyTrain network.

Nevertheless, not every city can make appropriate use of night buses. The important factors to consider include the following:

  1. How much does the rapid transit network follow major streets? If it mostly runs on two-way streets, as in Berlin, then running buss that duplicate the metro is easy. But if there are major deviations, especially if there are water crossings involved, then this is harder; in New York, where there are far more crossings of the East River by subway than by road, a night bus network would be virtually useless. Shuttle buses substituting for weekend trackwork are likewise complete failures whenever the subway is more direct than the streets, e.g. the Boston Red Line between Charles-MGH and Park Street.
  2. What is the expected size of the network? A minimum number of lines is required for success, and unless they are very frequent, transfers have to be timed. The half-hourly night buses in Berlin do not work well if untimed, for example.
  3. How long are the routes? This has two aspects. First, very long routes are less competitive with taxis if there are motorways. And second, a half-hourly night bus had better take around an integer number of half-hours minus turnaround time per roundtrip, to avoid wasting service hours. A 25-minute one-way trip is excellent, a 32-minute one a disaster.

45 comments

  1. Herbert

    Many tram systems, including most of Berlin’s, Dresden’s and Leipzig’s run 24/7. Why do you dismiss trams AGAIN?

    • Alon Levy

      How do the trams handle maintenance? I can’t imagine they single-track at night, since they run in mixed traffic. Do they do weekend closures?

      • Herbert

        In Dresden some routes had shutdowns or reroutings every once in a while due to maintenance. The Nuremberg subway (which does not do night service even on weekends) recently ran single track on its automated stretch (splitting U3 in two) during evenings for maintenance.

        I saw a documentary once on the Berlin tramway that made it seem that virtually all routine maintenance can be done while traffic keeps going. Unfortunately I cannot find it on YouTube right now…

      • Max Wyss

        There is not much maintenance with tram lines, as they essentially have a balastless track. And when (every 20 to 30 years) the rails have to be replaced, most of the work is done during normal operation time, and sometimes there will be a weekend shutdown.

        • Herbert

          It helps that they’re not in tunnels and usually don’t use complicated signaling systems…

        • Alon Levy

          In New York there’s direct fixation on the subway too (though not full slab, I don’t think?) and weekend shutdowns are ubiquitous.

          • Herbert

            The subway is in a tunnel. The tunnels are from (steel reinforced?) Concrete, which needs tons of maintenance.

            The only thing that has to be maintained for tram lines is the track and catenary itself

          • adirondacker12800

            You never noticed the rodents frolicking in the rivulet between the rails? .. .. on top of the layers of um um compost that have collected… That might be a monolithic piece of concrete but I wouldn’t call it a slab.

            The video of “Avocado Rat” is between the rails. The video of “Pizza Rat” is on the stairs. … you never noticed the rats? …
            Jeanne Moos of CNN on both of them:
            https://www.cnn.com/videos/us/2017/11/18/avocado-rat-moos-pkg-erin.cnn

            ….does look more like a lime to me and the stuff the rails are attached to looks woody. The Post says it’s Greenpoint Ave. G train! IND tracks.

          • michaelrjames

            adirondacker12800, 2019/06/11 – 00:07
            You never noticed the rodents frolicking in the rivulet between the rails? .. .. on top of the layers of um um compost that have collected… That might be a monolithic piece of concrete but I wouldn’t call it a slab.

            As a research scientist, let me invite you “up to my lab, and I’ll show you what’s on the slab”.. Rats are rather amazing beasts, especially lab rats who are more intelligent than the average Trump voter …

            But what’s happened to those Noo Yawk rats? Didn’t the SenesTech thing kill them off as promised? Probably not, as rats are extraordinarily good at survival, especially wherever there are humans. Here’s another tourist selfie:
            https://www.theguardian.com/world/2016/dec/19/marais-the-chic-paris-district-where-rats-outnumber-residents#img-1

          • Herbert

            The tunnels are also often pretty moist, which doesn’t help with maintenance either. Sometimes they’re below the water table or cross under bodies of water…

          • adirondacker12800

            I looked at the SenesTech site. All stuff we’ve been doing …. since farmers. Probably not put into an integrated system until the Victorian era, except for the birth control. The lazy fat females, who have been eating birth control, eventually die of old age, they’ll be replaced by rats that are outside the places where the bait has birth control in it. If there is no food the vermin don’t stick around. Cleaning up the food frequently costs money and that’s why people attempt poison and birth control. It keeps them down but the rats aren’t going to evolve to not-eat. Someone has to come and collect the trash ……before it starts to overflow… They were testing out a subway car sized vacuum cleaner, Keeping the tracks clean cuts down on the track fires and whisks away any rat food. Roach food that the rats don’t get.. Keeping on top of the food problem costs money. You don’t want to spend it, you will have rats. And mice and roaches and whatever else can find a niche in that ecosystem. Clean up the food. They’ll go away.

          • Herbert

            Is putting a lawn between tram tracks higher or lower maintenance?

  2. adirondacker12800

    American cities try to aim for 24/7 rail service

    Most American cities don’t have rail service. I suspect that people who don’t have it during day, don’t miss it at night.
    It’s NYC, the subway, the LIRR and PATH. Chicago on a few lines and PATCO. Three cities. Philadelphians yearn to have SEPTA run overnight again but I doubt they’ll get it.

  3. Gallia

    Hi Alon, thanks for this. I have to say I disagree with your description of the Paris system (“rarely” does segment shutdowns), or perhaps it was more accurate in the pre-2024-works era. I still think it’s a fantastic system, but there are regular shutdowns for planned works (and increasingly more so, at least in my impression). Other than the annual closure of the A that you mentioned (also applies for the C, that doesn’t really have a good alternative), at any given moment there are multiple shutdowns. Just in May, different segments of the B were closed every weekend; the 11 has hotel de ville as its terminus rather than Chatelet until December (considerably limiting its usefulness); service on line 4 stops early every night and starts later on Sundays (and occasionally has some stations along it closed for several months); Breguet-Sabin on the 5 is closed for the coming months; and Auber will be closed for the next 2 years. These are clearly important works (especially the automation of the 4 and the work on the A) and it’s not to say I think it could be done without these closures, but to say Paris has rare closures for work is inaccurate, in my opinion.

    • michaelrjames

      Right. Good summary. It seems like it might be especially intense at the moment? Part of an upgrade program?
      Except for the RER, the sheer density of the Paris metro network means there are always alternative routes to bypass any blockages. For the RER there is the Noctilien (night bus) which is a reasonable substitute (and it mostly shadows the RER network).
      Re M11 terminating at Hotel de Ville, its western exit is 100m from the eastern exit of Chatelet. Approx. a platform length. Unless you are American it isn’t too much of a slog:-)

      • Gallia

        Hi Michael, thanks for the reply. I don’t think it’s especially intense at the moment, as yes, it is part of the general upgrade in preparation to the 2024 Olympics (or you can say it’s a very long moment :P). Re the Noctilien and RER that’s correct, I guess I mixed segment shutdowns in general (RER C) and nighttime only (RER B, line 4; although both do both now), but still I think it proves my point that it’s not so rare in Paris, at least these days. And re line 11 – sure, but it’s not about getting to Chatelet (what on earth would one be doing there? ;)) but about transfer options – if you have to get out to the street (and pay for an extra ride, if you don’t have a monthly/weekly pass), even for a 100m walk, it’s a lot less practical… (and yes you can change to line 1 at HdV and take it one stop to Chatelet, but 2 transfers are way more inconvenient than 1). And finally, I’m not really complaining (or at least, not nearly as much as the average Parisian), just saying Paris these days doesn’t live up to its apparent reputation of “very rare” long-term closures.

      • Alon Levy

        It’s not Berlin 😉 – it may be a short walk but there are faregates, and if you live and work intra muros then you don’t have a reason to get a monthly because the breakeven point is too high.

        • michaelrjames

          Alon Levy, 2019/06/10 – 10:53
          … if you live and work intra muros then you don’t have a reason to get a monthly because the breakeven point is too high.

          Yeah, though the monthly pass now gives you Zones 1 – 5. It’s a new factor in the decision to rent intramuros or extramuros, since that €75/month Carte Navigo then looks like a bargain. Of course you will gnash your teeth when I tell you that for all my time in Paris I got my Carte Orange (Navigo precursor) at half price, as an awful lot of Parisians do. Having the total freedom of unlimited Metro use was great, and quite likely is one of those day-to-day things that makes one unconsciously love the place; if you don’t have it then I can see it might be a daily irritation. OTOH, if I return I will be exactly in your previous situation and may well just survive with a Carnet and have to think/plan any gadding about town. Sad. Unless I live extramuros which is looking increasingly likely. Even sadder.

          Incidentally, while one can discuss the temporary interruptions and ticket costs in Paris, New Yorkers would surely be utterly unsympathetic. Ditto Londoners? Maybe not Berliners, but it less than half their size and it seems is rapidly catching up in terms of cost of all the critical things (housing).

          • Herbert

            Berlin is debating some downright socialist policies re housing such as expropriation…

        • michaelrjames

          Forgot to mention: Australians own Paris at the moment! Go the Barty Party.

    • Alon Levy

      I should have said that individual station closures are pretty common (I think for M4 platform edge door installation but not just), and usually people can go to the adjacent station but sometimes the closed station is a key transfer like Chatelet. Sometime last winter Chatelet was closed on M4…

      • michaelrjames

        I wasn’t living there so I don’t know if there were earlier evening closures or weekend closures but it is pretty remarkable that M1 was so thoroughly retrofitted with platform doors and new signalling etc apparently without serious service interruptions.

  4. IAN! Mitchell

    I’d imagine there’s a huge disparity in men versus women in who is willing to use a night bus rather than a 24/7 rail system. Stations are familiar, well-lit, more commonly policed areas. Streets at night are none of these.

    Choosing night buses rather than overnight rail operations increases the pink tax.

    • Eric

      Is that true? Using rail, you have to use the streets anyway. And train stations are often full of long deserted passages and corners. And a bus always has a driver near at hand to protect against unruly passengers.

      • michaelrjames

        Yes, pretty creepy for anyone. But also note the differences. In Paris the stations and platforms are entirely free of columns and well lit, so no invisible lurkers. The NYC subway is positively menacing by comparison.
        Nothing is going to make late night totally safe for women, but at the same time we should realise that the vast majority of physical violence on the streets is against men!

    • RossB

      I wonder if agencies like New York would do better overspending on nighttime bus service, instead of trying to extend the operation of their trains. There is a tendency for agencies to spend very little on nighttime bus service (e. g. half hour buses running on a poor network). If you are working in the middle of the night, you probably have little flexibility with your schedule. You work the night or graveyard shift, and there is no value in showing up early (or staying late). In contrast, a day time professional can time their commuter train, show up 15 minutes early and start work immediately. This kind of service — especially in the middle of the night — is crap. I don’t care how well timed it is. The only people who use it will be those that simply can’t afford a cab or to own a car.

      All of this puts pressure on the agencies to extend the trains later and later. Even if they run less often, at least they run where people expect them to. For a city like New York, even an ideal nighttime bus system would lack the connections that the subway has, but that doesn’t mean it couldn’t be very good. It would simply require a new network — one suited for the surface streets at night. For a city like New York, the challenge is covering all the stations. The bus network wouldn’t necessarily follow the lines, but simply cover all the stations. For many riders, the trip would seem like a detour (and require a transfer) but something that kicks in at night (when traffic is light) could work well without breaking the bank. It would take time for people to adjust to two different systems (three if you count the regular bus service) but eventually people would get it. If the trains are closed, you walk to the surface and look for your bus (which should run every 10 or 15 minutes).

  5. Paul

    The Swiss do single-tracking for maintenance on mainline rail with adjacent tracks. The worksite I saw was at-grade with automated train-approaching warnings and a pretty high approach speed (maybe not full speed, but probably 80-90 km/h).

    BART could certainly run 24-hour service if they did something similar. They have crossovers at every station, low off-peak frequency on the branches (20 minutes or more), and the longest interstation travel time is 7 minutes in the Transbay Tube. They just don’t seem to know how to operate a rail system and have little to no curiosity about best practices elsewhere.

    • Herbert

      Well iirc they bought replacement parts off eBay once due to their bespoke Indian gauge system…

  6. Herbert

    Conceivable, but Sweden has no 40 000 km rail network, they never had Hartmut Mehdorn in charge and Sweden’s population density has a different distribution.

    Where less people live, less can impact the trains. Eurocities are often delayed in Hamburg due to something that happened in Budapest…

  7. Fbfree

    Alon, your last point is off the mark. Ensuring efficiency in pulsed networks is very important when the pulsed network forms the majority of the service provided. By definition, this is not the case at night. Rather, schedule reliability, span, and coverage over the daytime network tend to be more important than cost. Paying for a small number of extra operating hours to provide for 2 buses on a 32 minute route that optimize the former goals is likely to be worth it. This cost should not be compared to the cost of overnight service, but as it’s fraction of the cost of providing full-day service over the same destinations.

    • Alon Levy

      In Vancouver the night network is almost entirely pulsed (there’s a 20-minute bus on Kingsway outside the pulse system).

      Schedule reliability is actually less important. The way Ant6n explained this to me when I was working on NightBus in Boston was, the overnight network is only for about 5 hours each night, so there’s less time for delays to propagate than during the day. So if you have 26-minute one-way trips and hourly buses, it’s nbd if a small delay pushes the pulse point back by 2 minutes, because by the time these 2 minutes turn into (say) 7 minutes the night has ended and the daytime network is back.

  8. Max Wyss

    The ZVV night network started up as a bunch of night bus lines, primarily following the main tram routes, and extend to the suburbs. Despite the CHF5 surcharge for everybody, the night network got so popular that they started running S-Bahn services, with connecting buses.

    About maintenance: Most of “heavy maintenance” is done during the night, with complete shutdown between two stations, and bustitution of the last few trains (kind of past 22:00). This is communicated well ahead, and may lead to some adjustments on the “outer” segments. They aim to do such work during vacation times, so that traffic will be lower anyways. If I remember correctly, there are agreements between the SBB and local bus operators for such planned situations.

    • Herbert

      Apparently the only thing that keeps Nuremberg S-Bahn from having night service is that Munich isn’t moving on the issue. Operationally and financially there are no impediments.

      But then again Munich hates Franconia

  9. Hugh B

    There’s a bit of good and bad in terms of your principles with metro in DC in terms of the network, so do you think it would be effective?

    • Herbert

      Nuremberg metro has a rather long stretch of single track (between Ziegelstein and Flughafen) where drivers trains have been running since 2010. The stretch had been used by driver operated trains since 1999.

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