When Buses are a Poor Guide to Corridor Demand

Vancouver is going to open the Evergreen Line at the end of the year, an 11-km SkyTrain branch to Coquitlam with a projected ridership of 70,000 per weekday; current ridership on the B-line bus paralleling the route, the 97, is 11,000, the 20th busiest citywide (see data here).

New York is going to open the first phase of Second Avenue Subway at the end of the year or early next year, a total of 4 km of new route with projected ridership of 200,000 per day (see pp. 2-3). The bus running down First and Second Avenues, the M15, has 46,000 weekday riders, trading places with two other routes for first citywide, but first phase only covers a quarter of the route, and the ridership projection in case the entire Second Avenue Subway is built is 560,000; nobody expects the other two top bus routes in New York, the B46 on Utica and the Bx12 on Fordham, to support such ridership if they’re ever replaced with subways.

In Boston, the Green Line Extension northwest in Somerville is projected to have 52,000 weekday riders by 2030. There is no single parallel bus, but a few buses serve the same area: the 101 with 4,800 weekday riders, the 89 with 4,200, the 88 with 4,100, and the 87 with 3,800 (all bus ridership data is from the Bluebook, PDF-pp. 48-54); the busiest of these ranks 28th regionwide.

In all three cases, I think the ridership estimates are reasonable. Vancouver especially has a good track record, with Canada Line ridership meeting projections; it’s harder to tell in New York and Boston, which have not opened a rail line recently (New York’s 7 extension was just one stop, and its predicted ridership explicitly depends on future development). Since in general I do think cities should plan their rail extensions around where the busiest buses are, I want to talk about the situations that create a disjunction.

I mentioned in two past posts that rapid transit that surface transit and rapid transit alignments obey different rules, with respect to street geometry. In the more recent post, I used it to argue that tramway corridors should follow buses. In the older post, I argued that subways can take minor detours or go under narrower, slower streets to reach major destinations, for example Century City in Los Angeles, which is near the Wilshire corridor but not on it. However, the latter case isn’t quite what’s happening in any of the three examples here: Second Avenue Subway follows Second Avenue (though phases 1-2 diverge west to serve Times Square, which is important), and the Green Line Extension and Evergreen Line’s routes are both straighter than any bus in the area.

The situation in Boston and Vancouver is not that there’s an arterial bus that misses key destinations. Rather, it’s that the street network is inhospitable to buses. Boston is infamous for its cowpaths: only a few streets, such as Massachusetts Avenue, are wide and long enough to be reasonable corridors for arterial buses, and as a result, the bus network only really works as a subway feeder, with very high rail to bus ridership ratio by US standards. The corridors that do support busier buses – in the Greater Cambridge sector, those are the 77, 71, and 73 buses – are defined by the presence of continuous arterials more than by high latent travel demand.

Vancouver, of course, is nothing like Boston. Its bus grid is Jarrett Walker‘s standard example of an efficient, frequent bus grid. But this is only true in Vancouver proper, and in parts of Burnaby. In the other suburbs, either there’s an arterial street grid but not enough density for a good bus grid (Richmond, Surrey), or there’s no grid at all (Coquitlam). There’s a bus map of the Port Moody-Coquitlam area, with the 97-B line in bright orange and the 5-roundtrips-per-day West Coast Express commuter rail line in purple; the Evergreen Line will run straight from Port Moody to Coquitlam along an alignment parallel to the railroad, whereas the 97-B has to take a detour. Overall, I would class Coquitlam and Somerville together, as places where the street network is so bad for buses that rail extensions can plausibly get a large multiple of the ridership of existing buses.

Second Avenue Subway phase 1 partly belongs in this category, due to the difficulty of going from Second Avenue to Times Square by road, but high projected ridership on phase 3 suggests something else is at play as well. While First and Second Avenues are wide, straight throughfares, functioning as a consistent one-way pair, two factors serve to suppress bus ridership. First, Manhattan traffic is exceedingly slow. The MTA is proud of its select bus service treatments, which boosted speed on the M15 between 125th and Houston Streets to an average of about 10 km/h; in contrast, the Bx12 averages 13-14 km/h west of Pelham Bay Parkway. And second, the Lexington Avenue Line is 360 meters, so riders can walk a few minutes and get on the 6 train, which averages 22 km/h. The Lexington trains are overcrowded, but they’re still preferable to slow buses.

Now, the closeness to the Lexington trains can be waved away for the purposes of the principle of this post: I am interested in where preexisting transit ridership is not a good guide to future transit ridership, and in this example, we see the demand via high ridership on the 4, 5, and 6 trains. However, the issue of slow Manhattan traffic can be folded generally into the issue of circuitous street networks in Boston and Coquitlam.

It makes intuitive sense that the higher the bus-to-rail trip time ratio is, the higher the rail line’s ridership is relative to that of the bus it replaces. But what I’m saying here goes further: the two mechanisms at hand – a street network that lacks continuous arterials in the desired direction, and extensive traffic congestion – reduce the effectiveness of any surface solution. Is it possible to build tramways in the Vancouver suburbs? Yes. But in Coquitlam (and in Richmond and Surrey, for different reasons), they would be circuitous just like the buses. This also limits the ability of bus upgrades to solve transportation problems in such areas.

Now, what of New York? In theory, a bus or tram with absolute signal priority could run down the Manhattan avenues or the major outer-borough throughfares at high speed. But in practice, there is no such thing as absolute signal priority on city streets. It’s possible to speed up surface vehicles via signal priority, but they’ll still have to stop if cross-traffic blocks the intersection. In Paris, the tramways are not fast, averaging around 17-18 km/h, even though they have dedicated lanes and run on wide boulevards in the outer parts of the city and in the inner suburbs; in contrast, Metro Line 14, passing through city center, averages almost 40 km/h.

The implication here is that when a city develops its subway network, it should pay attention not just to where its busiest surface lines are, but also to which areas have intense activity but have suppressed surface ridership because the roads are slow or circuitous. These are often old city centers, built up before there were cars and even before there was heavy horse wagon traffic. Other times, they are general areas where the road network is not geared toward the desired direction of travel.

In cities without subways at all, there is a danger of overrelying on surface traffic, because such cities often have old cores with narrow streets, with intense pressure for auto-oriented urban renewal as they get richer. This is less common in the developed world, but nearly every developed-world city of note either has a rapid transit network already or is completely auto-oriented and has no areas where the road network is weak. Israel supplies several exceptions, since its transportation network is underdeveloped for how rich it is; in past posts I have already voiced my criticism of the decision to center the Tel Aviv Subway around wide roads rather than the older, often denser parts of the city.

In cities with subways, it’s rarely a systemic problem. That is, there’s rarely a specific type of neighborhood that can support higher rapid transit ridership than preexisting transit ridership would indicate. It depends on local factors – for example, in Somerville, the railroads are oriented toward Downtown Boston, but the streets are not, nor are they oriented toward good transfer points to the subway. This means transit planners need to carefully look at the road network for gaps in the web of fast arterials, and consider whether those gaps justify transit investment, as the GLX and Evergreen Line do.


  1. Fbfree

    For the SAS and the Evergreen line, while the buses that directly follow the corridor have suppressed ridership, parallel transit corridors take up the slack, and provide a decent predictor of ridership on the new service. In the case of the Evergreen line, it will provide a faster and more frequent alternative to the 160 bus up Barnet Highway, the 169 along Lougheed Highway, and, to a partial extent, the 159 along Como Lake Rd.

  2. Eric

    Another (more minor) factor is that by extending a rail line, you eliminate the bus-rail transfer penalty along the extension.

    • Alon Levy

      They’re not a grid – they’re a radial system converging at SkyTrain.

      They’re also a really weak project. They’re being studied (and will be funded) purely because Surrey feels that if Vancouver gets money for a Broadway subway, Surrey should also get some rail money. It’s the same inferiority complex that drives BART to San Jose and Diridon Intergalactic.

      • Brendan Dawe

        All the words that the Province have put together or approved on the subject seem to telegraph that Victoria does not approve of Surrey LRT (such as de-specifying the ballot language from last year’s referendum from ‘Light Rail”to “Rapid Transit” to repeated insistence on how great business cases should be to translink’s claimed half-billion dollar negative social value and so forth) and they have a long history of upgrading light rail proposals that local governments have attached themselves to.

        Ottawa is not terribly picky, and the Mayors need Victoria’s approval to do much of anything, if they don’t want it they’ll wont have it.

  3. anony-moose

    On a slightly related note, I was looking at the bus map for Honolulu. Now that is an interestingly spastic bus system. The geography of the city seems to make public transit difficult. They’re building a rail transit line, but I know very little about it.

    Click to access TheBusSystemMap.pdf

    • Alon Levy

      I did not see this, thanks!

      I doubt it’ll happen, because construction in Israel is slow, and the political system likes to do radical changes every time a new minister comes in; Israel Katz will thankfully not be minister of transportation forever. That said, Radial 3 is really useful – I think it’s a good corridor that has depressed bus ridership because there’s no straight, wide street like Jabotinsky. It needs to extend 1-2 stops farther west to hit Jaffa and the Red Line, but that’s easy to fix. Radials 1 and 2 look like regional rail in the Ayalon corridor?

      • Shamir

        Radial 3 would be better as an extension of the purple line. (Yes, in a tunnel, since the surface roads here are limited.)

        The whole plan here looks horribly duplicative of both the under-construction light rail (which is really a subway in the central parts) and the already-built commuter/intercity railroad. It is as if Katz is just drawing lines on the map at random in order to provide concrete-pouring opportunities for the construction firms.

  4. Adam

    This is true of fairfax avenue in Los Angeles. It has heavy bus ridership, which makes it a leading route candidate for the Crenshaw northern extension. But the heavy bus ridership is an illusion caused by the West LA transit center (it isn’t a center it’s, a bus refueling depot tucked underneath the interstate 10 freeway on fairfax). Tons of buses going every direction radially from this point terminate at this location, including the fairfax bus line, my experience was about two to three buses per minute depart the bus stop. If you have to take a bus any long distance in LA you’ve probably changed buses here. Fair fax ridership is about the connecting value of the WLA transit center, not about the superiority of its corridor destinations.

    Fairfax is also narrow, only one lane each direction, passing through single family residential, historic little Ethiopia, and A long huge array of old folks homes for most of its route north or interstate ten, but it is a rare north south arterial in LA making it invaluable for traversing a length of the city. There are three destinations, lacma at Wilshire blvd, the upscale grove shopping mall and the small employer cbs television city (I’ve worked there, and the surface parking lots surrounding the buildings are sufficient to supply the entire facility, so you could easily count the lots on google maps). These destinations are the usual argument in favor of a fairfax rail route, which is insane to me. The more easterly la brea avenue has lower bus ridership, but a major boom in dense residential construction along it and rapid turnover and development along the corridor, it’s also a wide three lanes in each direction street and is the north south artery for cars (whereas the narrower more congested fairfax is the dominant bus artery). In terms of corridor demand, la brea is clearly superior.

    But rail advocates continue to persist in the path dependency of the fairfax option, probably because they visit lacma once every five years, and thinks connection there would be fun. I say path dependency because originally, the subway was supposed to run north on fairfax to Hollywood, so it’s a thirty year old path for some reason.

    Politically, fairfax was so opposed, federal and state laws were passed prohibiting it as a route and subway construction in LA stopped for twenty years because of the power of these nimbys. But rail advocates still seem to prefer it over superior corridors, often justifying the bus ridership numbers. LAstill has an anti fairfax route law on the books, that prevents sales tax collected for metro from some old Measures authorizing the taxes from being spent on any subway construction

    • Jerard

      Adam, that was asinine pretzel logic written there.

      If you’re argument is that the West LA transit center “artificially” inflate the numbers on the Fairfax corridor then how do you explain the large transfers off of other bus lines like Venice, Pico, Olympic, Wilshire, 3rd, Beverly, Melrose, Santa Monica and Sunset Blvd having high spikes of on/off boardings at Fairfax. How do you also explain why the 217 goes to the Expo Line station if based on your logic it doesn’t need to go south of Washington Blvd? Is it because of the destinations AND dare I use the other D word, Density of destinations and trips that will make an extension on this corridor so vital. Something that if you were to configure a northern extension this is the logical place to route such a corridor.

      This is the equivalent of saying lets build the Purple Line down Olympic Blvd instead of Wilshire because Wilshire’s ridership numbers are artificially inflated because so many people work along the corridor and wait for the bus on that corridor. Or the same logic that others are using to justify why a rail corridor on Vermont would work because it is the second busiest corridor in the Metro system but based on the assumptions you make doesn’t justify a rail on an already busy corridor.


  5. Pingback: When Buses are a Poor Guide to Corridor Demand, Redux | Pedestrian Observations
  6. Pingback: IBX Cannot be a Tram | Pedestrian Observations

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