Boston NightBus: Planning Around Timed Connections

Over the last year, several people at the Boston advocacy group TransitMatters have been working on a plan to restore night bus service in the area, which is one of few big US cities with no transit between 1 and 5 am. See here for the original concept, from March of last year. The TransitMatters plan assumes limited financial resources, designing the plan around eight or nine routes, all running on an hourly takt schedule, meeting at one central location for a pulse, currently planned to be Copley Square. This seems fairly standard: in Vancouver, too, the daytime bus grid is replaced with a pulse-based system at night, with 30-minute headways on most lines.

So far, so good. The problem is that after additional work, including checking travel times on Google Maps but also some nighttime test drives, TransitMatters found that the original map would not work with an hourly takt. Hourly service with one vehicle per route requires one-way travel time to be 30 minutes minus turnaround time. Double-length routes, at one hour minus turnaround times, can also fit into the system, with two vehicles, but nothing in Boston is that long. Several of the routes turn out to be just a hair too long, and the plan evolved into one with 75-minute headways, too long and irregular for customers. In meetings with stakeholders, the relevant members of Transit Matters were told as much, that 75 minutes was too low a frequency.

I started doing work on this plan around then. Since I think a clockface schedule is important – especially if there’s money for more buses, because then the headways would be 30 minutes and not an awkward 37.5 minutes – I started to sketch ideas for how to reduce travel time. The revisions center the schedule, fitting route choices around the need for buses to complete the roundtrip in an hour minus two turnaround times; this is what I came up with. Time is saved by avoiding detours, even to relatively major destinations, and by not going as far as would be ideal if there were no need to maintain the takt. Many of the design principles are generally useful for designing takt-based schedules, including for commuter rail and for rail-bus connections.

Schedule padding should be based on expected punctuality

This is a point I’ve made before in talking about LIRR scheduling, where fragile timetabling contributes to high schedule padding. Overall, punctuality depends on the following possible attributes of transit services:

  • Rail is more punctual than buses, and electric service is more punctual than breakdown-prone diesels.
  • Grade-separated transit is more punctual than surface transit.
  • Services are more punctual when there are fewer riders, especially buses, which only stop when riders request it.
  • Surface transit is more punctual if it has dedicated lanes, or if (as on some Vancouver routes) it runs on a street with signal priority over intersecting traffic.
  • Surface transit is more punctual off-peak, especially at night, when there’s no congestion.
  • Transit service is more punctual the shorter the span is: a system that’s only supposed to run for 5 night hours has less room for schedule slips than one that’s supposed to run for 21 daytime hours. (This I credit to Ant6n.)

While NightBus involves surface buses running in shared traffic lanes using on-board fare collection, the expected traffic is so low that travel time is likely to be close to the travel time depicted on Google Maps without traffic, and significant variations are unlikely. This means it’s possible to get away with less schedule padding, even though the plan requires 8 routes to converge at one pulse point. The maximum one-way travel time should be taken to be around 26 minutes. 24 minutes is better, and ideally not all routes should be 26 (they’d wait for one another at the pulse point, so it matters how many routes are near the maximum and not just what the maximum is).

Routes should run as fast as necessary and as far as possible

Sometimes, the optimal routing is already the fastest – for example, maybe it really is optimal to link two nodes with a nonstop route. Usually, it is not: on rapid transit there are intermediate stops, on surface transit there are detours and slower segments when freeways are available. When the schedule is tight, there is a plethora of tradeoffs that must be made about travel time. A detour to a major destination, so important that in isolation it would improve service despite the slowdown for through-passengers, must be weighed against other detours. On fast commuter rail line, where there is a significant stop penalty, the equivalent is the intermediate stop; I discussed this 5 years ago in the context of the Lowell Line. The overall length of the route is also a variable: when possible, the outer end should be as far as possible while maintaining the takt.

In the context of NightBus, I used this rule for all routes:

  • The N17, running parallel to the Red Line to Ashmont, runs straight on Dorchester Avenue, whereas in the original plan it detoured to serve Kane Square; there is no time to detour to Kane Square, so in the revised plan it skips it, and passengers going there would need to walk 500 meters.
  • The N28, running on Washington Street and Blue Hill Avenue, terminates at the future Blue Hill Avenue commuter rail stop, and not the Mattapan trolley stop. At night the trolleys don’t run, so the connection isn’t important, and the few hundred meters cut from the route give the buses 2 crucial minutes with which to make the 26-minute one-way schedule.
  • The N32/39 cannot go on Huntington (N39) and thence to Hyde Park (N32); it can either go on Huntington to less valuable Roslindale or on a route parallel to the Orange Line to Hyde Park. I believe the latter option is better, but this is up for debate.
  • The N57 follows the Green Line B Branch to Boston College (taking 20 minutes), not the 57 into Watertown (which would take about 27); I think this is also the optimal decision independently of the need to make the pulse, but the pulse makes it far better. Note that this means the route would have to use unmarked bus stops, since in the daytime there is no bus paralleling the B Branch.
  • The N1 terminates at Davis Square, without going farther into Cambridge or into Arlington (as N77).
  • The N82 and N110 use Storrow Drive to skip Downtown Boston’s slow streets. The buses run on a pulse, so there is no need for more than one bus to serve the same route – they’d be scheduled to bunch, rather than overlying to provide higher frequency. The N111 to East Boston, Chelsea, and Revere serves Downtown Boston instead. This cuts service from Downtown to Malden and Medford, but Downtown is a 9-5 neighborhood, so there’s less need to connect it in every direction at night.
  • The N111 terminates in central Revere and not in North Revere.

Not all transit services are meant for all social classes

At night, buses go at approximately the same speed as cars, provided cars can’t take freeways. If the cars are carrying multiple passengers, as ride-sharing counterproposals plan to, then they probably can’t take freeways. In theory, this means buses would be for everyone, since they were as fast as taxis. In practice, this is only true for people using one route – diagonal trips are still faster by taxi. But worst, the hourly frequency is brutal. People who can plan their night travel around the schedule would use the bus; so would people who can’t afford taxis. But people in the top two-thirds of the income distribution are unlikely to use NightBus, or any ride-sharing alternative (if ride-sharing can afford more vehicles for higher frequency, so can buses).

What this means is that the service needs to be designed around the needs of low-income riders. As a note of caution, in popular parlance there’s a tendency to conflate low-income riders with other groups, such as elderly riders, and pit their needs against good transit practices like wider stop spacing, off-board fare collection, frequent grids, and so on. Those practices are applicable to everyone, and if they appear to favor middle-class riders, it’s because when the buses are too slow, the middle class drives and the poor keep taking the bus, so faster buses have higher proportions of richer riders.

With that caveat in mind, what I mean when I talk about low-income riders is the distribution of origins and destinations. The various draft plans proposed by Transit Matters members all focused on serving lower-income neighborhoods. This is why it’s not such a problem that the N1 only goes as far as Davis Square: that is the favored quarter of the Boston area, and the areas cut off from service, such as Arlington, are rich enough that few would ride an hourly or even half-hourly bus. Additional decisions made based on this principle include,

  • The N32/N39 route serves Hyde Park and not Roslindale. At equal incomes, I’d probably suggest serving Roslindale, which makes for a shorter route, and allows the route to use the extra time gained to get to Forest Hills via a longer route on Huntington and pass near Longwood. But incomes are not equal: Roxbury is much poorer than Longwood and Jamaica Plain, and Hyde Park is poorer than Roslindale.
  • The N57 serves Boston College, which is middle-income but still poorer than Watertown.
  • The N111 serves Chelsea, and probably would regardless of average incomes, but it could instead go parallel to the Blue Line, serving somewhat less poor and less dense areas.

The schedule’s importance is higher at lower frequency

None of the above principles really matters to a subway with 2-minute peak headways and 4-minute off-peak headways. Some of these subways don’t even run on a fixed schedule: it’s more important to maintain even headways than to have trains come when the nominal schedule says they will.  The point where clockface scheduling starts to become important seems contentious among transit planners. Swiss planners use clockface schedules down to (at highest) 7.5-minute headways, and say that 11-minute headways are a recipe for low ridership. In Vienna and Berlin, timed transfers are offered on the U-Bahn on 5-minute trains. At the opposite end, hourly and even half-hourly services must be designed around a schedule with quick connections, to prevent passengers from having to wait the full headway.

In borderline cases – the 7.5-15 minute range – transfers can be timed, and at the less frequent end some overtakes, but there is no real need to design the rest of the schedule around the headway. The main reason to operate with tight turnarounds is to reduce fleet and crew requirements. Any looseness in the schedule, beyond the minimum required for punctuality and crew comfort, should be thought of as a waste. However, the waste is capped by the overall headway. Concretely, if your favorite transit route takes 31 minutes one-way after factoring in turnaround time and schedule padding, then it needs 2 vehicles to provide hourly service, lying idle half the time; to provide 10-minute service, it needs 7 vehicles, lying idle only 11% of the time. So if frequency is high enough, the route should be designed without regard to turnaround times, because the effect is reduced.

But NightBus is hourly; 30-minute service is aspirational. This means that the schedule is more important than anything else. Even if a single neighborhood feels genuinely screwed over by the decisions made to keep the routes at or under 26 minutes – for example, if Revere and Mattapan prefer service going farther out even at the cost of 70- or 75-minute frequency – good transit activists must think in systemwide terms. Maintaining the hourly takt throughout the service area is more important than North Revere and the last few hundred meters in Mattapan.

Ultimately, buses and trains are not all that different

There are major differences between buses and trains in capital costs, operating costs, reliability, and so on, leading to familiar tradeoffs. Even at medium-size transit systems such as the MBTA, frequent bus networks are convoluted and at times fully gridded, while rapid transit networks are invariably radial at least to some extent,. Buses also can’t consistently use timed transfers at high frequency.

However, there are many similarities, especially with small bus networks, which are designed around a pulse rather than a grid:

  • Public transit works with transfers and central dispatching. This makes it better at pulse-based network than any taxi (including ride-hailing apps) or ride-sharing service.
  • Vehicles are large – not to the same extent of course, but relatively speaking (trains in large cities, buses in small ones or at night). There’s less room for the everywhere-to-everywhere one-seat rides that taxis provide at higher cost. If there’s budget for more service-hours, it’s spent on higher frequency or longer routes and not on adding more one-seat rides.
  • Routes are centrally planned, with decisions made about one area affecting service in other areas. It is not possible for routes to evolve by private spontaneous action except in the thickest markets, far bigger than what small bus networks can support.
  • The importance of the schedule and of timed transfers is proportional to the headway, and inversely proportional to frequency.

This is good news, because it means that the large body of good industry practices for rail planning, inherited from such countries as Switzerland and Japan, can be adapted for buses, and vice versa. I did not invent the principle of running trains as fast as necessary; it’s a Swiss planning principle, which led the country to invest in rail just enough to enable trains to go between Zurich, Basel, and Bern in one hour minus turnaround and transfer time. Nor did I expect, when I started getting involved in Transit Matters, that this would be so helpful in designing a better bus plan.

26 comments

  1. Bjorn

    As demand is asymmetrical depending on the time of night, with demand to home (from the customer’s perspective) ending at the hub end around 2 am, and demand from home starting at 4 am, it’s probably possible to expand coverage by extending the shifts of buses that currently end earlier. As an example, a block that currently goes out of service at 2:00 could be sent on a one-way route to a residential area, arriving at the garage around 3:00; a block that goes into service at 5:00 could pull out an hour earlier and start from the distant residential area at 4:00. Of course, no ‘reverse-flow’ service would likely be scheduled, but demand from people needing to go to work (or anything else, really) at 2:00 am or that clock out at 4:00 am is very minimal. A side benefit (or drawback, depending on your perspective) to one-way overnight routes is that the service would be intentionally unusable for people riding for “non-transportation purposes,” as they would face a lengthy outside layover in a residential area around three in the morning.

    An option would be to divide the network into two types of routes, a group of all-night subway and key bus route duplicators that run every 20-30 minutes or so between busy night activity centers (colleges, clusters of bars, Logan Airport, etc), and a group of peripheral one-way routes described above that leave from a handful of mini-hubs at the edge of the area that can justify all-night service.

    • Alon Levy

      Bear in mind that the proposed network is pretty much an all-night subway duplicator running every hour. The N111 doesn’t quite duplicate the Blue Line because there’s more travel demand out of Chelsea than out of Revere Beach – the Blue Line is just where there happened to be a rail ROW – but it still should be thought of as a rail duplicator, so that six out of eight of the routes follow a subway line, and a seventh follows the Green Line Extension. This eight-route, hourly plan is projected to cost $3.5 million a year, and even that the MBTA is not sure it wants to spend; we are working on trying to convince it of the benefits of night service.

      The other thing is that Boston already has some early-morning routes, starting at 4 am or so. Some of them are really busy, for example out of Chelsea.

      There’s likely to be less demand between 2 and 4, but by this point papering over the gap is useful purely from a scheduling perspective: you really want the drivers and buses to just be able to go back and forth for a night shift.

      What are “non-transportation purposes” for riding? People don’t ride for fun. I guess suburban NIMBYs hate the idea of access by bus sometimes, but none of the routes really passes by any rich suburban area. (That said, they don’t seem to mind on the West Side of Vancouver.) The map is in part gerrymandered to avoid areas where rich people live, like most of Greater Cambridge, purely because they’re so unlikely to use these buses that the money is better spent on Chelsea, Dorchester, and Roxbury.

  2. Colin V. Parker (@ColinVParker)

    That late at night, all service is infrequent, and a pulse system makes sense. During the day, however, much of the service is frequent, so there is little to gain from pulsing, but there are still routes that are infrequent. In these cases, the same question arises on the infrequent routes as to whether to use clockface or run the otherwise optimal route. Only now, the context is different, as connections would usually be to frequent service and therefore untimed. But, just as a pulse system *could* use 75/37.5 minute headways or be trimmed to run 60/30, an individual route could do the same. Would you advocate trimming (or expanding) routes to try to maintain clockface scheduling? There’s also a tricky part with clockface, where if you are running every 30 minutes off-peak, your only logical upgrade is to 15 minutes on-peak, because if you switch to 20 minutes, the schedule is pretty tricky to commit to memory. E.g. the bus leaves at 8:18,8:48,9:18,9:38,9:58, etc.

  3. Matthew

    It’s not normal for buses to use Storrow drive due to low bridges. Did you check that your proposed route avoids the low bridges? I can’t quite tell from the diagram.

    Also, the primary users of the Allston/Brighton bus will be students, and it will be the most crowded route. The previous incarnation of late night T bore that out.

    Maybe this website will be useful for ridership data halfway thru the previous attempt of late night service: http://mrd.github.io/LateNightT/

    • Nathan Williams

      Yeah, the height limit/bus restriction on Storrow seems like a problem.

      (As do some one-way streets – as shown, the N92 and N101 routes look OK going outbound, but they’d clearly need a different route inbound.)

      • Alon Levy

        The map intentionally only depicts outbound routes. Inbound routes are for the most part similar, but yes, there are some differences with the N92 and N101. The big change is that one short street segment would need to be made two-way. But otherwise it’s not too different, and conversely the N111 is actually a bit easier inbound than outbound.

    • Alon Levy

      If I’m understanding this right, the low bridges are all west of the proposed segment. I’m not sure what the clearance is under the Longfellow Bridge on the Storrow side; on the Memorial side it’s 11′, which is borderline but will clear a bus with a 2″ margin (yes, I know). On eyeballing, everything else on the route looks definitely fine.

  4. Martin

    While you’re looking to keep each trip down to 26 mins, one optimization could be derived if your ridership is asymmetric. For instance, more people are probably leaving downtown than coming in. This will make the outbound trip longer, say 30 mins, but if few people take the bus inbound, the trip time might be down to 22 mins. Since you only need to Pulse in one direction, it’s ok for the inbound run to depart at say 3:34am.

  5. Oreg Meyer

    I’m not sure the assumption about the rich not taking a night bus holds. Rich kids also want to drink and hate being the designated driver. Isn’t party traffic the main target market for this service?

    • Alon Levy

      No, party traffic is not the target market. Party traffic carpools in taxis. Some of the people in that demographic wouldn’t even take a night bus, or for that matter an evening train, at equal travel time. Our target market is late-night shift workers – the people working at the party spaces, not the people attending them. The people who work at the restaurants and bars in Back Bay and at Central Square don’t live there. It’s also for people who start working very early in the morning, such as the large crowds on the 4 am buses out of Chelsea.

      • Oreg Meyer

        Oh, I see. That’s a fundamental difference to the night services I know in Europe then. There, the party kids are the focus. An ideal night service would serve both groups, I guess.

          • Matthew

            Barcelona is the only city I can think of offhand that does 24 hour metro for a weekend night, and they only run for Saturday night if I recall correctly. London has just begun rolling out Night Tube on selected lines, so there’s that.

            A bit odd that the Spanish cities like Madrid shut down Metro at 0200 (Cercanías even earlier) considering that most partiers there aren’t even getting started until after midnight. I guess they keep going until after 0600 anyway though.

            As far as I know most European cities rely on night bus networks after 1230 – 0100 or so.

          • Oreg Meyer

            Only a few of the biggest European cities keep their subways running on weekend nights. Most rely on night buses instead: Paris, Amsterdam, Munich, Frankfurt, Madrid, Rome, Milan, Oslo etc.
            However, as all this is a rather recent trend that is little more than 15 years old, the service is still evolving in many cities.

          • Matthew

            Add Copenhagen to the list as well, as their slick new automated rapid transit operates 24/7.

  6. Oreg Meyer

    How about a circumferential night route? One that connects islands of night life might justify a higher frequency than hourly so it might work as a feeder for the radial pulse.
    Probably not a priority for Boston, but how about cities that already have radial night service?

    • Alon Levy

      In Vancouver I suspect that they probably should redo their night network to have a route that runs straight on Broadway, unlike the current regime where one route runs West Broadway-Downtown and another runs East Broadway-Downtown. The workhorse daytime circumferentials – the 25, 41, and 49 – are also possibilities, especially the 41, but I’m skeptical. The reason is that, as in Boston, the target market is really not high-income party goers, and the West Side circumferentials all pass through really rich areas. I can sort of see a mega-N41 going between UBC and Metrotown, but how much night traffic is there out of UBC? The campus is dead after hours. Metrotown, maybe… but then people wouldn’t be going from there to the West Side, and to the core East Side destinations, the N19 should be fine.

      In Boston, the system we’re proposing is really skeletal. If there’s money for a 9th route, it should go to the airport. If there’s money for a 10th or 11th route, it should follow the alternative options considered for the 8 main routes, i.e. N39 along Huntington to Roslindale, and/or a route on Bennington duplicating the Blue Line. If there’s twice as much money as we’re asking the MBTA to commit, it should go to 30-minute service. If there’s even more money, it should go to lengthening some routes so as to run 30-minute service with 3 buses rather than 2: longer versions of the N111, N28, N1, and N17 in that order. I might not even consider circumferential routes until the radials were up to 20-minute frequencies. Boston doesn’t have a lot of strong circumferential corridors; the 1 south of Back Bay and the 66 are about the only ones, and the 66 travels through areas where the expected night ridership is zero.

      • Oreg Meyer

        Thanks much for the detailed reply. Sounds like there’s nothing fundamentally wrong with considering a circumferential route in principle, but it heavily depends on the circumstances in the particular city and often there will be many other options with higher priorities. Makes sense.

      • Matthew

        Massport should be operating and funding night access to the airport. I’m not sure why they aren’t doing it already. It would get used very well, certainly by people stranded after 12:30 am. Massport has the money and the motive; their sponsorship of the Silver line (free for riders coming from the airport) has been a great success.

        I think that you are discounting the 1 and 66 maybe a bit too much. While I agree with your overall points, I also know that I have seen both those buses busy late at night. The 66 in particular has a tendency to run late after normal service hours have ended. I used to see route 66 buses roaming the streets in revenue service past 2 am and that was in the years before Late Night T! Propagating delays is my guess on that.

  7. threestationsquare

    1) I think it’s very valuable to follow daytime major bus routes where possible, for legibility to riders as well as operational convenience (stop locations, driver training, etc).
    2) The airport is a major employer of late night/early morning shift workers so serving it seems vital.
    3) Google Maps says Kenmore to Watertown Yard along the 57 route takes 22 minutes without traffic, but the early morning 57 runs are scheduled to take only 17-18, so even with an extra 6 minutes from Copley to Kenmore I think the full 57 route is feasible? (Similarly, Google says 22 minutes from Copley to Forest Hills along the 39 route without traffic, but the early-morning 39 trip is scheduled to take only 18.)
    4) There are a couple worthwhile routes long enough to justify two busses.
    In light of the above, I made this modified map based on yours. It does require nine vehicles while your proposal only requires eight (Ari’s original proposal required eleven).

    I worry a bit about whether Copley is the best place for busses and passengers to wait. It seems like the off-street bus terminal area at Back Bay Station might be better, especially if the indoor passenger waiting area could be made available. But the street layout means that getting in and out of the terminal would add several minutes to the run time of several of the proposed routes, necessitating cuts at the outer ends to maintain the hourly timetable, which doesn’t seem worth it. That’s probably the next best option if using Copley turns out to be infeasible for some reason though.

    • Alon Levy

      The two long routes that use two vehicles are somewhat strange. I guess that you need the N117 to be this convoluted in order to get to Revere and Wonderland (if you split it into two one-vehicle routes, you get to Revere and the airport but not Wonderland), but the N101 can safely be split in two, with one route going to Malden and the other to Medford. Apparently the early-morning routes to Malden are pretty busy, so you’d definitely want a direct route, doing the trip in half an hour minus turnaround time, rather than an hour minus turnaround time.

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