Anti-Infill on Surface Transit

I wrote about infill stops on commuter rail two weeks ago, and said I cannot think of any example of anti-infill on that mode. But looking at Muni Metro reminded me that there is need for anti-infill on surface transit. This is called stop consolidation normally, and I only use the term anti-infill to contrast with the strategy of adding more stops on commuter trains.

The root of the problem is that in North America, transit agencies have standardized on 200-250 meters as the typical spacing between bus stops. In Europe, Australasia, and East Asia, the standard is instead 400-500 meters. Even without off-board fare collection, the difference in speed is noticeable. In Vancouver, the difference between the local 4 and the express 84 is substantial: on the shared segment between Burrard and Tolmie, a distance of 4.8 km, the 84 makes 5 stops and takes 10 minutes, the 4 makes 18 stops and takes 16 minutes. A bus with the normal first-world stop spacing would make 10-12 stops and take, linearly, 12-13 minutes. 23 km/h versus 18 km/h.

With off-board fare collection, the impact of stop spacing on speed grows. The reason is that a bus’s stop penalty consists of the time taken to stop and open its doors, plus the time it takes each passenger to board. The former time is independent of the fare collection method but depends on stop spacing. The latter time is the exact opposite: if the stop spacing widens, then there are more passengers per bus stop, and unless the change in stop spacing triggers changes in ridership, overall passenger boarding and alighting time remains the same. Another way to think about it is that judging by Vancouver data, there appears to be a 30-second stop penalty, independent of ridership. Off-board fare collection increases bus speed, so the 30-second stop penalty becomes more important relative to overall travel time; the same is true of other treatments that increase bus speed, such as dedicated lanes and signal priority.

In New York, there aren’t a lot of places with local and limited-stop buses side by side in which the limited-stop bus has on-board fare collection. One such example is the M4, meandering from Washington Heights down the 5th/Madison one-way-pair, over 15.3 km. At rush hour, the local takes 1:45, the limited-stop takes 1:30: 9 vs. 10 km/h. But the limited-stop bus runs local for 6 km, and over the other 9.3 km it skips 26 local stops if I’ve counted right. The B41 has a limited-stop version over 8.3 km (the rest is local), skipping about 17 stops; the time difference is 10 minutes.

One possible explanation for why the stop penalty in New York seems a little higher than in Vancouver is that the M4 and B41 routes are busier than the 4/84 in Vancouver, so every stop has at least one passenger, whereas the 4 in Vancouver often skips a few stops if there are no passengers waiting. Conversely, the higher passenger traffic on buses in New York comes from higher density and more traffic in general, which slows down the buses independently of stopping distance.

On subways, there’s reason to have more densely-spaced stops in denser areas, chief of which is the CBD. On surface transit, it’s less relevant. The reason is that absolute density doesn’t matter for stop spacing, except when expected ridership at once station is so high it would stress the egress points. What really matters is relative density. Putting more stops in an area means slowing down everyone riding through it in order to offer shorter station access times to people within it. On surface transit, relative density gradients aren’t likely to lead to variations in stop spacing, for the following reasons:

  1. Historically, surface transit stop spacing was always shorter than rapid transit stop spacing because of its lower top speed and the faster braking capabilities of horses vs. steam trains; often people could get off at any street corner they chose. So it induced linear development, of roughly constant density along the corridor, rather than clusters of high density near stations.
  2. If there is considerable variation in density along a surface transit line, then either density is medium with a few pockets of high density, which would probably make the line a good candidate for a subway, or density is low with a few pockets of higher density, and the bus would probably skip a lot of the low-density stops anyway.

Most importantly, the 400-meter standard is almost Pareto-faster than the 200-meter standard. In the worst case, it adds about 4 minutes of combined walking time at both the start and the end of the trip, for an able-bodied, healthy person not carrying obscene amounts of luggage. The breakeven time on 4 minutes is 8 skipped stops, so 3.2 km compared with the 200-meter standard. Bus trips tend to be longer than this, except in a few edge cases. In New York the average unlinked bus trip is 3.4 km (compare boardings and passenger-km on the NTD), but many trips involve a transfer to another bus or the subway, probably half judging by fare revenue, and transfer stations would never be deleted. If the destination is a subway station, guaranteed to have a stop, then the breakeven distance is 1.6 km.

This also suggests that different routes may have different stop spacing. Very short routes should have shorter stop spacing, for example the 5 and 6 buses in Vancouver. Those routes compete with walking anyway. This may create a spurious relationship with density: the 5 and 6 buses serve the very dense West End, but the real reason to keep stop spacing on them short is that they are short routes, about 2 km each. Of course, West End density over a longer stretch would justify a subway, so in a way there’s a reason short optimal stop spacing correlates with high bus stop density.

The situation on subways is murkier. The stop penalty is slightly higher, maybe 45 seconds away from CBD stations with long dwell times. But the range of stop distances is such that more people lose out from having fewer stops. Paris has a Metro stop every 600 meters, give or take. Some of the busiest systems in countries that were never communist, such as Tokyo, Mexico City, and London, average 1.2 km; in former communist bloc countries, including Russia and China, the average is higher, 1.7 km in Moscow. The difference between 600 meters and 1.2 km is, in the worst case, another 1.2 km of walking, about 12 minutes; breakeven is 16 deleted stops, or 20 km, on the long side for subway commutes.

One mitigating factor is that subway-oriented development clusters more, so the worst case is less likely to be realized, especially since stops are usually closer together in the CBD. But on the other hand, at 1.2 km between stations it’s easy for transfers to be awkward or for lines to cross without a transfer. London and Tokyo both have many locations where this happens, if not so many as New York; Mexico City doesn’t (it’s the biggest subway network in which every pair of intersecting lines has a transfer), but it has a less dense network in its center. Paris only has three such intersections, two of them involving the express Metro Line 14. Even when transfers do exist, they may be awkward in ways they wouldn’t have been if stop spacing had been closer (then again, Paris is notorious for long transfers at Chatelet and Montparnasse).

In all discussions of subway stop spacing, New York is sui generis since the lines have four tracks. On paper its subway lines stop every 600-700 meters when not crossing water, but many trains run express and stop every 2 km or even more. Average speed is almost the same as in Tokyo and London, which have very little express service, and it used to be on a par until recent subway slowdowns. This distinction, between longer stop spacing and shorter stop spacing with express runs, also ports to buses. Buses outside the US and Canada stop every 400-500 meters and have no need for limited-stop runs – they really split the difference between local and limited buses in North America.

On a subway, the main advantage of the international system over the New York system is obvious: only two tracks are required rather than four, reducing construction costs. On a bus line, the advantages are really the same, provided the city gives the buses enough space. A physically separated bus lane cannot easily accommodate buses of different speeds. In New York, this is the excuse I’ve heard in comments for why the bus lanes are only painted, not physically separated as in Paris. Mixing buses of different speeds also makes it hard to give buses signal priority: it is easy for buses to conflict, since the same intersection might see two buses spaced a minute apart.

Buses also benefit from having a single speed class because of the importance of frequency. In Vancouver, the off-peak weekday frequency on 4th Avenue is an 84 rapid bus every 12 minutes, a 44 rapid bus every 20 minutes, and a local 4 every 15 minutes. The 84 keeps going on 4th Avenue whereas the 4 and 44 divert to Downtown, but the 4 and 44 could still be consolidated into a bus coming every 10 minutes. If there were enough savings to boost the 84 to 10 minutes the three routes could vaguely be scheduled to come every 5 minutes on the common section, but without dedicated lanes it’s probably impossible to run a scheduled service at that frequency (pure headway management and branching don’t mix).

The example of 4th Avenue gets back to my original impetus for this post, Muni Metro. Only diesel buses can really run in regular surface mode mixing different speed classes. Trolleys can’t. Vancouver runs trolleys on the local routes and diesels on the limited routes. At UBC, it has different bus loops for diesels and trolleys, so people leaving campus have to choose which type of bus to take – they can’t stand at one stop and take whatever comes first.

On rail, this is of course completely impossible. As a result, American subway-surface trolleys – the Boston Green Line, SEPTA’s Subway-Surface Lines, and Muni Metro – all run at glacial speed on the surface, even when they have dedicated lanes as in Boston. In Boston there has been some effort toward stop consolidation on the Green Line’s busiest branch, the B, serving Boston University. This is bundled with accessibility – it costs money to make a trolley stop wheelchair-accessible and it’s cheaper to have fewer stops. Muni Metro instead makes one stop every 3-5 accessible (on paper), but keeps stopping at all the other stops. It would be better to just prune the surface stops down to one every 400-500 meters, which should be accessible.

If you view rail as inherently better than bus, which I do, then it fits into the general framework: anti-infill on surface transit has the highest impact on the routes with the best service quality. Higher speed makes the speed gain of stop consolidation more important relative to travel time; trolleywire makes it impossible to compensate for the low speed of routes with 200-meter interstations by running limited-stop service. Even on local buses, there is never a reason for such short stop spacing, and it’s important for North American cities to adopt best industry practice on this issue. But it’s the most important on the highest-end routes, where the gains are especially large.

31 comments

  1. BDawe

    have you ever found anything suggesting that the improved acceleration of electric buses has meaningful travel time benefits?

    • Bjorn

      I’m mixed in opinion. On one hand, acceleration is mostly limited by passenger comfort, not technology. Us bus operators have to be smoother with our acceleration or deceleration than one would be driving in their car alone or customers like yourself start to complain, especially if you are standing!

      On the other hand, a fully-loaded bus is noticeably slower to accelerate; the additional burst of power that an electric motor can generate would be very useful here.

      There’s also slight difference in acceleration rates between bus vintages in my employers’ fleet, even if the buses are nearly the same otherwise.

    • Max Wyss

      It is not really the acceleration, where trolleybuses do shine; it is when it comes to steeper and longer grades.

      Another aspect is already mentioned by Bjorn. Electric drives allow for a smoother acceleration than hydro-mechanical or hydraulic drives (the first deviation of the acceleration curve becomes smaller). With that, higher acceleration can be made more bearable. Although a good driver can achieve smooth accelerations with a hydro-mechanical drive.

  2. Michael James

    My city has introduced a special type of bus service called “Glider” (its icon is the glider possum, I suppose being that it glides you from one tree to the other bypassing the ground-level congestion; almost). It is a semi-express stopping at only one out of about 3-4 regular stops. You can’t buy tickets on this bus so must have a travel card but this allows faster boarding and also means you can board at the main front door and the middle doors.

    Paris has a Metro stop every 600 meters, give or take. Some of the busiest systems in countries that were never communist, such as Tokyo, Mexico City, and London, average 1.2 km; in former communist bloc countries, including Russia and China, the average is higher, 1.7 km in Moscow.

    I know you know this but: The Paris Métro has inter-station spacing ≈0.7 km (214km/303 stations); RER is ≈2.28 km (587/247) while combined system av.≈1.4km. So in fact a bit wider spacing than those other cities, possibly because the RER was designed anew and not locked into legacy stations(?). …Slaps head… no of course, in the Paris suburb of Villejuif where I worked, every second street is named after Paul Vaillant-Couturier, Maxime Gorky, Louis Aragon, Léo Lagrange and Jean Jaurès: obviously it was communist town planning 🙂 In fact most of these leftist luminaries have their names on stations of the M7 extension into the banlieu where the stations are much more widely spaced than in intra-muros Paris.

    • Alon Levy

      Oh, of course there’s the RER here. But then there’s commuter rail in London and Tokyo, with four-track mainlines with express trains (eight tracks if you’re Tokyo). The local/express transfers on the subway in New York are cross-platform, whereas here they range from meh (Nation) to illegal under the Geneva Conventions (Chatelet).

  3. Iskandar

    From the rail+property perspective (“shape” in addition to “serve”):

    “The greatest weakness of bus routes might be their relatively low cost; it is too easy to trade frequent service for wide coverage, and it is too easy to add stops; spreading out boardings reduces the ability of any one stop to support pedestrian oriented commerce. The result is that bus systems usually do not promote articulation/concentration of commerce and the built environment.”

    ~ https://janejacobsjapan.com/2017/08/16/bus-before-rail-defies-historical-experience/

  4. Henry Fung

    More of the recent faux-BRT routes have dropped the idea of running a local underlay service and just running the “limited” stop route with half mile/0.7 km spacing, like Seattle Rapid Ride, Stockton Metro Express, Vancouver (WA) Vine, etc.

  5. Untangled

    On to normal commenting, that last one was crazy.

    While the stops in SF may be close together, one of the mitigating factors in SF is that they have all door loading on all routes on the Muni system, not just selected routes like the NY SBS, it probably doesn’t help at every single stop but it does at the busier stops.

    Aside from the things you’ve already mentioned and all door loading, another thing that would be helpful to speed up buses would be to order buses with an extra door at the back. It probably isn’t ideal with the low-entry buses that are prevalent in North America but a number of cities in Europe (Paris isn’t one apparently) use low-floor buses that have 3 or 4 doors on a standard 12 meter bus and up to 5 doors on a 18 meter articulated bus. The extra door helps decrease the time stopped. Another benefit of a 3 door low-floor bus layout (as opposed to low-entry), it encourages more passengers to spread out inside the bus to stand instead of hanging around and overcrowding the low-floor section of a low-entry bus which means extra room to stand on busy services.






    You could, of course, try a 3 door low-entry bus it’s kind of terrible like this one in Singapore.

    This article places a lot of emphasis on stop spacing being a culprit of slow average bus speeds, and it is, but it’s not the only one (to be fair, it was the title though). If North American cities want to adopt “best industry practice”, there’s a lot more they need to look at. Even though SF was the impetus of the article, SF is actually far ahead of any other North American city in terms of “best industry practice”, because they do all door boarding on all routes. They just need 3 door low-floor buses and stop consolidation now. If Vancouver consolidated stops between Burrard and Tolmie (in the first example) to 10-12 stops as you suggest but employed all door loading with 4 door low-floor buses (no low-entry), they would probably manage to get it to fit in the travel time down to the old 5-stop limited-stop service.

    Only diesel buses can really run in regular surface mode mixing different speed classes. Trolleys can’t.

    This can be solved by having 2 “lanes” of trolley wires. You can either put in at the stops where the bus overtakes slower buses or the entire way with wire switches every now and then. This is something Vancouver could use if they insist on keeping local-limited buses. The (future) problem with trolleybuses is that they are electric and battery technology is progressing quite well, so unless it’s a legacy trolley system, best to go with battery.

    • Alon Levy

      Nice has three-door 12-meter buses! So does Florence.

      All-door boarding indeed speeds up buses. But it actually makes the argument for stop consolidation stronger rather than weaker. At busy stops where passengers have to board at the front and pay, dwell time is dominated by the number of passengers rather than by the bus’s acceleration and deceleration time. So consolidating stops doesn’t save as much time relative to overall travel time. The faster the bus, through low floors, all-door boarding and POP, dedicated lanes, and signal priority, the bigger the speed gain from anti-infill.

      • Eric

        Something I’ve noticed locally is that if only 2 or 3 people board the bus at the front, the driver can close the door and drive off immediately. Whereas if 10 people are boarding at the same stop, they all have to wait in line to pay, and the door can only be closed after 7 or 8 have paid. I think this negates your line “it actually makes the argument for stop consolidation stronger rather than weaker”.

        • Eric

          Actually, thinking about it a bit more, I was wrong. Feel free to delete my above comment (and this)

          • Alon Levy

            …I don’t think this is wrong, actually. You’re giving a counter to my model of bus dwell times: I model them in the post as a fixed amount of time (around 30 seconds) plus a variable amount of time which is linear in the number of passengers. You’re saying that the actual variable time is instead linear in (pax – 3), which means that consolidating two stops with at least 3 passengers each to one stop saves less time than 30 seconds. It’s not wrong. I think it’s a minor factor, since three people paying the driver adds maybe 5-7 seconds with New York MetroCards and less with smartcards, but it’s still something to account for.

            The one weird thing about this is, Vancouver has a smart card, and before it did, most passengers had a paper monthly pass they showed to the driver. The rest dipped tickets like they do in New York. This suggests the stop penalty in Vancouver should be higher than in New York. But actually the opposite is true: the 4th Avenue buses to have a 30-second penalty and the Broadway buses much less (even though the limited has all-door boarding and the local doesn’t!), whereas in New York the penalty looks more like 35-40 seconds.

        • Bjorn

          In the US, driver’s can’t (well, shouldn’t) take off immediately. It’s against federal law to have passengers standing forward of the standee line.

          Enforcement of this rule tends to vary at the agency level; it’s common practice in larger cities (Chicago and Denver are the two I have the most first-hand experience with) for drivers to openly disregard this law and take off while riders are still paying their fares.

      • Untangled

        Nice has three door buses! Wow, RATP seems provincial compared to Nice, I hope it’s low-floor, not low-entry. Three door buses seem to be more prevalent in Central European countries though.

        Stop consolidation does fit very nicely with all door boarding in reducing travel time.

        Try getting this on your standard North American bus though.

    • BDawe

      Vancouver actually has ‘express’ trolley wires on Hastings Street, though they’ve grown a lovely copper patina.

      The the problem is that on a six-lane arterial lake Hastings, the wires (as currently located) are too far from the curb for express buses to make stops (and stops would entangle with local buses anyway) and so they replaced the former non-stop express trolley with a limited stop diesel artic some decades ago, though the wires are still in place and are used for the occasional non-revenue move

    • Max Wyss

      I think what you see in the Lausanne picture is that the lines do deviate, and that the separation switch has been placed in a “better” location, allowing the to get to its correct lane at a better time. So, it is not really a “local-express” situation we have here.

  6. Pingback: To Restore Walkability, Cities Like Akron Need to Look Beyond Sidewalks – Streetsblog USA
  7. ckrueger99

    As part of the planning for trolley (streetcar) upgrades on SEPTA, the DVRPC did analysis on the likely impact of stop consolidation, signal priority and 2-door boarding. It’s theoretical, but interesting. 2-door boarding assumes no driver assist with wheelchair boarding. The whole shebang results in about 20% time saving on inbound route, 15% on outbound. Read here: http://www.dvrpc.org/reports/15005.pdf

  8. Patrice

    No trolley system runs slower than New Orleans. My god! A driver who dispenses tickets, steeps stairs for boarding, lines, a top speed of what seemed like 25 mph, street running.

    • newtonmarunner

      You obviously haven’t been to Boston. See Green E on Huntington Ave. past Brigham & Women’s Hospital. It beats even the Green B. The only reason the Green E is faster than the 39 bus is because the 39 bus gets stuck behind it.

    • Joey

      Yeah I recall it being pretty bad when I was there – maybe competitive with walking if you’re feeling tired.

  9. newtonmarunner

    I generally agree that LRT beats BRT. The one advantage I can give BRT over LRT is resiliency in a 2+ lane busway where the buses can go around each other if one breaks down. Also, cost-wise, if very little capacity is needed, I’d argue BRT every 3-5 minute headways during rush hour is preferable to 10 minute rush hour headways on a 1-car LRT train; 10 minute headways on a one-car train during rush hour can turn into 20 minute headways during non-rush hour. That said, for a city like Boston where transit demand is high(er), LRT is preferable to BRT. BRT in Boston just paves a right-of-way for LRT; e.g., 28X bus, Summer St. and Broadway BRT, etc.

    Boston (and NYC) need a lot of work on getting their bus/LRT stops further apart. No need, for example, for there to be 3 stops between Coolidge Corner and Washington Sq. and another 3 stops between Washington Sq. and Cleveland Circle. No need for the #1 bus to stop more than once between Harvard and Central Sq. and no need for the #66 crosstown bus to stop (or at most once) between each of the Harvard Ave. LRT stops.

    [rant over]

    • Alon Levy

      More to the point, about BRT paving the right-of-way for LRT: I don’t think this is really true. Look at Iskandar’s comment above, with the link. It makes the point that this never happens; on Twitter we discussed this a bit, and I could find examples of subways built under or over BRT corridors (e.g. the Millennium and Canada Lines in Vancouver), but no light rail using the same infrastructure. Los Angeles is not railstituting the Orange Line, even though it was supposed to be built to be rail-ready, because such construction would create too much short-term disruption.

      In Boston, the various corridors you cite aren’t really good BRT-to-LRT corridors. Summer is great for BRT, but wouldn’t really support LRT without big long-term investment creating a new subway trunk in Downtown Boston. A 28X reservation could turn into an F-Line reservation, but evidently nobody’s using the (unenforced) bus lanes on Washington for a shorter F-Line to Dudley; one of the area organizations scoring capital projects, I forget which, sandbagged the F-Line citing unrealistically low ridership estimates.

      • threestationsquare

        Edinburgh converted a 1.5km busway into part of their LRT line using the same infrastructure (it was open less than 5 years 2004-2009). Seattle converted their downtown tunnel from bus to bus+LRT with plans to convert it to LRT-only. Portland added LRT to the pre-existing bus lanes on their Transit Mall.

      • Jarek

        Ottawa is rebuilding core Transitway as LRT, though it is indeed very disruptive and thus potentially an exception that only strengthens the main rule…

  10. Pingback: Week in review: August 26, 2017 | TriTAG

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s