Bus Stop Spacing and Network Legibility

I had an interesting interview of the annoying kind, that is, one where my source says something that ends up challenging me to the point of requiring me to rethink how I conceive of transportation networks. On the surface, the interview reaffirmed my priors: my source, a mobility-limited New Yorker, prefers public transit to cars and is fine with walking 500 meters to a bus stop. But one thing my source said made me have to think a lot more carefully about transit network legibility. At hand was the question of where buses should stop. Ages ago, Jarrett suggested that all other things equal (which they never are), the best stop spacing pattern is as follows:

The bus stops on the north-side arterials are offset in order to slightly improve coverage. The reason Jarrett cites this doesn’t occur much in practice is that there would also be east-west arterials. But maybe there aren’t a lot of east-west arterials, or maybe the route spacing is such that there are big gaps between major intersections in which there’s choice about which streets to serve. What to do then? My source complained specifically about unintuitive decisions about which streets get a bus stop, forcing longer walks.

In the case of the most important streets, it’s easy enough to declare that they should get stops. In Brooklyn, this means subway stations (whenever possible), intersecting bus routes, and important throughfares like Eastern Parkway or Flatbush. Right now the B44 Select Bus Service on Nostrand misses Eastern Parkway (and thus the connection to the 3 train) and the M15 SBS on First and Second Avenues misses 72nd Street (and thus the southernmost connection to Second Avenue Subway). However, there is a bigger question at hand, regarding network legibility.

Bus networks are large. Brooklyn’s current bus network is 550 km, and even my and Eric Goldwyn’s plan only shrinks it to about 340, still hefty enough that nobody can be expected to memorize it. Passengers will need to know where they can get on a stop. For the sake of network legibility, it’s useful to serve consistent locations whenever possible.

This is equally true of sufficiently large subway networks. Manhattan subway riders know that the north-south subway lines all have stops in the vicinity of 50th Street, even though the street itself isn’t especially important, unlike 42nd or 34th. In retrospect, it would have been better to have every line actually stop at 50th, and not at 49th or 51st, but the similarity is still better than if some line (say) stopped at 47th and 54th on its way between 42nd and 59th. A bad Manhattan example would be the stop spacing on the 6 on the Upper East Side, serving 68th and 77th Streets but not the better-known (and more important) 72nd and 79th.

There are similar examples of parallel subway lines, some stopping on consistent streets, and some not. There are some smaller North American examples, i.e. Toronto and Chicago, but by far the largest subway network in the world in a gridded city is that of Beijing. There, subway stops near city center are forced by transfer locations (Beijing currently has only one missed connection, though several more are planned), but in between transfers, they tend to stop on consistent streets when those streets are continuous on the grid.

But outside huge cities (or cities with especially strong grids like Chicago, Philadelphia, and Toronto), consistent streets are mostly a desirable feature for buses, not subways. Bus networks are larger and less radial, so legibility is more important there than on subways. Buses also have shorter stop spacing than subways, so people can’t just memorize the locations of some neighborhood centers with subway stops (“Nation,” “Porte de Vincennes,” etc.).

In the other direction, in cities without strong grids, streets are usually not very long, and the few streets that are long (e.g. Massachusetts Avenue in Boston) tend to be so important that every transit route intersecting them should have a stop. However, streets that are of moderate length, enough to intersect several bus lines, are common even in interrupted grids like Brooklyn’s or ungridded cities like Paris (but in London they’re rarer). Here is the Paris bus map: look at the one-way pair in the center on Rue Reaumur and Boulevard Saint-Denis (and look at how the northbound bus on Boulevard de Strasbourg doesn’t stop at Saint-Denis, missing a Metro transfer). There are a number of streets that could form consistent stops, helping make the Parisian bus network more legible than it currently is.

As with all other aspects of legibility, the main benefits accrue to occasional users and to regular riders who unfamiliar with one particular line or region. For these riders, knowing how to look for a bus stop (or subway station, in a handful of large cities) is paramount; it enables more spontaneous trips, without requiring constantly consulting maps. These occasional spontaneous trips, in turn, are likelier to happen outside the usual hours, making them especially profitable for the transit agency, since they reduce rather than raise the peak-to-base ratio. (Bus operating costs mostly scale with service-hours, but very peaky buses tend to require a lot of deadheading because they almost never begin or end their trip at a bus depot.)

The main takeaway from this is that bus network redesigns should aim to stop buses on parallel routes at consistent streets whenever possible, subject to other constraints including regular stop spacing, serving commercial nodes, and providing connections to the rail network. To the extent cities build multiple parallel subway lines, it’s useful to ensure they serve stations on consistent streets as well when there’s a coherent grid; this may prove useful if New York ever builds a subway under Utica and extends the Nostrand Avenue Line, both of which extensions were on the drawing board as recently as the 1970s.

9 comments

  1. Mike

    Even worse, Vancouver’s trolleybus stops in opposite directions are often not at the same cross street. An example is the 20 on Commercial, where the northbound and southbound stops are at alternating streets. Most of the southbound stops are at intersections without traffic lights, making it difficult to cross, especially for older people who are less able to walk to an intersection with a light. This pattern increases the effective walking distance to transit, even with a map.

    The obvious solution is to consolidate bus stops at intersections with traffic signals and to add traffic signals to match the stopping pattern of the bus.

    • Alon Levy

      Yeah, Vancouver’s unsignaled intersections are pretty bad this way. Part of the problem is that, at least on the West Side, the main streets are placed at perfect intervals for a subway: Cambie, Oak, Granville, Arbutus, MacDonald, Alma. For a bus, they’re too wide, unless you’re going for a rapid overlay designed around low turnover, i.e. the 99-B or the 84. Consolidating the 9 and 99 would probably mean compromising on stop spacing, making about twice as many stops as the 99 today, and then some of the interpolating stops, like Vine, aren’t great for pedestrian crossing.

      The ultimate solution is to have physically separated median bus lanes with boarding islands, like on Odengatan, so that pedestrians only have to cross half the street at a time. But that requires telling the drivers that they don’t get the same priority in their single-occupant car as a bus packed with 70 passengers hurtling toward UBC.

  2. Fbfree

    Two rejoinders.
    1- Alternating stop layouts aren’t necessarily less legible. One could construct a stop layout on a numbered grid where any given bus route stops every 5 blocks, with a different offset to each route. That would provide legibility similar to what clockface scheduling provides.
    2- Given a route where there are constraints on a large fraction of the stops, the ideal stop location then becomes the bisection of two enforced stop locations. (In the case of a consolidated 9/99, one would ideally have a stop at Balsam, if there we’re a light there, instead of at Vine.)

    • Alon Levy

      Both of your rejoinders are true. But, ad 1, the issue is that things are rarely so clean that you can construct a perfect offset. In practice you’ll be intersecting an east-west arterial every few stops, and then the question is how to interpolate stops between the forced locations. For example, in Brooklyn, if I have an east-west route on Avenue J and another on Avenue M, which are about 800 meters apart, do I interpolate a stop on Avenue L on all north-south routes, a stop on Avenue K on all north-south routes, or a mixture?

      • HerkimerSnediker

        I prefer Fbfree’s mnemonic to yours because it doesn’t increase distance and thus impact coverage. It couldn’t be universally applied but then you’ve qualified your approach with multiple constraints as well.

        Since subway stations usually span at least two short blocks we’d have more wiggle room there. Think what fun we could have had laying out stations on the midtown trunks. Lines 4 through 6 run up Lexington so we could have placed the stations between #4 and #6 streets; The 1 thru 3 go up 7th and then Broadway so there we’d place them between #1 and #3 streets; the 6th and 8th Ave. lines combine on CPW so naturally they’d be between #6 and #8 streets. Much easier to grok than 125th, 116th, 110th, 103rd….

        And yes I do hang my shirts up by color. But what to do with the plaids?

  3. Oreg

    Have you ever written about bus networks in smaller cities with no subway? I recently looked at Rüsselsheim, Germany, a financially strained city of 64,000 in the center of the Rhine-Main region, surrounded by Frankfurt, Wiesbaden, Mainz, Darmstadt. No grid, constrained by a huge car factory (Opel), a river, a train line and an autobahn. Other than 1 1/2 train stations they have only buses and their network looks highly irregular: https://www.stadtwerke-ruesselsheim.de/de/Privatkunde/Busverkehr/Busverkehr1/Busstreckenplan-600×300.pdf
    It seems hard to find guidelines for cities like that. Maybe you’d have a pointer?

    • johndmuller

      That Rüsselsheim bus map certainly shows at least a skeleton of a pattern – i.e all the lines go to the Railway station, the red makes a big loop to the east, the yellow a closer in loop to the east, the orange, blue and purple go north, south and west respectively to serve identifiable suburbs, and the green does its own thing in the south southeast direction. If those color codes are actually marked somehow on the buses, stops, and destination signs, that’s enough to get around with, more or less.

      What I find to be the killer problem with buses in general is that they can and do make surprising digressions from the straight and narrow and take you to God knows where and only maybe return to the yellow brick road that you thought you were on. Now the same sort of thing could happen to you on a streetcar, where you might go off on a tributary, but (a) you can see the switches coming, so they are not a complete surprise, and (b) you know that if you want to get back to the main route, just take a car in the opposite direction and it has to go back there (so long as you have not yet crossed any other lines), since there is only that one set of tracks, not the seemingly endless possibilities of the road system. This adds a lot to one’s feeling of security.

      Since the light rail ROW is built to be at least semi-permanent, they’re not going to want to immortalize the kind of drunkard’s walk routing that finds its way into many bus routes. Consequently, the tramway will end up being more direct and thus make it easier for strangers to predict where it will go.

      • Oreg

        Thanks for your comment, John.
        I was wondering about, e.g., if there are better ways than to let all lines end at the train station (Hbf). The Friedensplatz stop is walking distance from the station (350 m). If that where the hub (with only a few lines continuing to the train station), buses could make single-seat connections between neighborhoods and suburbs on opposite sides of the center.
        The red and yellow lines are loops but they are not circumferential w.r.t. the city center, i.e., they make no useful connections to radial lines. But this big-city approach will be difficult to pull off in smaller cities as distances are shorter and, therefore, the relative price of connections is higher.
        What’s the best practice for medium-sized cities? Fast radial lines on the big arterial roads combined with slower circumferential lines through the neighborhoods? Or mostly neighborhood lines as in Rüsselsheim? How to think about the trade-off between a hub at the train station and a hub somewhere else in the city center? Should connections be avoided at all cost? Is there significant traffic between neighborhoods or should all lines simply get riders to the center or train station as quickly as possible? Should suburb lines go through neighborhoods on their way to the center or skip them as fast as possible?

  4. Pingback: Our Brooklyn Bus Redesign | Pedestrian Observations

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