Little Things That Matter: Vertical Circulation

Chatelet-Les Halles has a problem with passenger circulation. It has exceedingly wide platforms – the main platforms, used by the RER A and B, are 17 meters wide – but getting between the platform level and the rest of the station runs into a bottleneck. There are not enough stairs and escalators between the platform and the mezzanine, and as a result, queues develop after every train arrival at rush hour. Similar queues are observed at the Gare du Nord RER platforms. The situation at Les Halles is especially frustrating, since it’s not a constrained station. The platforms are so wide they could very easily have four or even six escalators per access point flanking a wide staircase; instead, there are only two escalators, an acceptable situation at most stations but not at a station as important as Les Halles.

This is generally an underrated concern in the largest cities. In smaller cities, the minimum number of access points required for coverage (e.g. one per short subway platform, two per long platform) is enough even at rush hour. But once daily ridership at a station goes into the high five figures or the six figures, a crunch is unavoidable.

There are two degrees of crunch. The first, and worse, is when the capacity of the escalators and stairs is not enough to clear all passengers until the next train arrives. In practice, this forces trains to come less often, or to spread across more platforms than otherwise necessary; Penn Station’s New Jersey Transit platforms are that bad. The situation at Les Halles and Gare du Nord is a second, less bad degree of crunch: passengers clear the platform well before the next train arrives, but there’s nonetheless a significant queue at the bottom of the escalator pits. This adds 30-60 seconds to passenger trip times, a nontrivial proportion of total trip time (it’s a few percent for passengers within the city and inner suburbs). Avoiding even the less bad crunch thus has noticeable benefits to passengers.

The capacity of a horizontal walkway is 81 passengers per minute per meter of width (link, p. 7-10). This is for bidirectional travel. Unidirectional capacity is a little higher, multidirectional capacity a little lower. Subway platforms and passages are typically around 5 meters wide, so they can move 400 passengers per minute – maybe a little more since the big crunch is passengers heading out, so it’s unidirectional with a few salmons (passengers arrive at the station uniformly but leave in clumps when the train arrives). Busier stations often have exits at opposite ends of the platform, so it’s really 400*2 = 800. Queues are unlikely to form, since trains at best arrive 2 minutes apart, and it’s uncommon for a train to both be full and unload all passengers at one station.

An escalator step can be 60 cm, 80 cm, or 1 meter wide, with another 60 cm of handrail and gear space on both sides. On public transit, only the widest option is used, giving 1.6 meters of width. The theoretical capacity is 9,000 passengers per hour, but the practical capacity is 6,000-7,000 (link, p. 13), or 100-120 per minute. This is more than pedestrian walking capacity per unit of step width, but less per unit of escalator pit width. So a pedestrian walkway ending in a battery of escalators will have a queue, unless the width of the escalator bank is more than that of the walkway leading to it.

Moreover, escalators aren’t just at the end of the station. The busiest train stations have multiple access points per platform, to spread the alighting passengers across different sections of the platform. But mid-platform access points have inherently lower capacity, since they compete for scarce platform width with horizontal circulation. It appears that leaving around 2 meters on each side, and dedicating the rest to vertical circulation, is enough to guarantee convenient passenger access to the entire platform; in a crunch, most passengers take the first access point up, especially if there’s a mezzanine (which there is at Les Halles).

Should New York invest in better commuter rail operations, it will face a bigger risk of queues than Paris has. This is for two reasons. First, New York has much higher job density in Midtown than Paris has anywhere, about 200,000/km^2 vs. perhaps 100,000 around La Defense and the Opera (my figures for both areas in Paris have huge fudge factors; my figure for New York comes from OnTheMap and is exact). And second, Manhattan’s north-south orientation makes it difficult to spread demand across multiple CBD stations on many commuter rail lines. One of the underrated features of a Penn Station-Grand Central connection is that through-trains would have passengers spread across two CBD stops, but other through-running regional rail lines would not have even that – at best they’d serve multiple CBDs, with one Midtown stop (e.g. my line 4 here).

When I computed the needs for vertical circulation at a Fulton Street regional rail station in this post, I was just trying to avoid the worse kind of crunch, coming up with a way to include 16 platform-end escalators (12 up, 4 down in the morning peak) and 16 mid-platform escalators (8 up, 8 down) on a 300-meter long two-level station. It’s likely that the escalator requirement should be higher, to avoid delaying passengers by 1-1.5 minutes at a time. With four tracks (two on a Grand Central-Staten Island line, two on a Pavonia-Brooklyn line) and 12-car trains arriving every 2 minutes, in theory the station could see 240,000 incoming passengers per hour, or 4,000 per minute. In reality, splitting passengers between Grand Central and the Financial District on what I call line 4 means that a sizable majority of riders wouldn’t be getting off in Lower Manhattan. When I tried to compute capacity needs I used a limit passenger volume of 120,000 per hour, and given Midtown’s prominence over Lower Manhattan, even 90,000 is defensible.

90,000 per hour is still 1,500 per minute, or 3,000-4,000 if we are to avoid minute-long queues. A single up escalator is limited to about 100-120 people per minute, which means that twenty up escalators is too little; thirty or even forty are needed. This requires a wider platform, not for horizontal passenger circulation or for safety, but purely for escalator space, the limiting factor. I proposed an 8-meter platform, with space for four escalators per end (two ends per platform, two platforms on two different levels), but this suggests the tube diameter should be bigger, to allow 10-meter platforms and six escalators per end, giving four up escalators per end. This is 16 up escalators. Another 16-20 up escalators can be provided mid-platform: the plan for eight up escalators involved eight access points interspersed along the platform, and 10-meter platforms are wide enough width to include three escalators (two up, one down) per bank and on the border of allowing four (three up, one down).

The situation at the Midtown stations in New York is less constrained. Expected volumes are higher, but Grand Central and Penn Station both spread passengers among multiple platforms. In the near term, Penn Station needs to add more vertical circulation at the New Jersey Transit platforms. The LIRR remodeled its section of the station to add more access points in the 1990s (e.g. West End Concourse), but New Jersey Transit is only doing so now, as part of phase 1 of Moynihan Station, and it’s still not adding as many, since its platforms are shorter and don’t extend as far to the west.

Nonetheless, given the number of proposals out there for improving Penn Station, including ReThinkNYC and Penn Design’s plan, it’s important to think of longer-term plans for better vertical circulation. When I proposed eliminating Penn Station’s above-ground infrastructure, I came up with a design for six approach tracks (including a new Hudson tunnel connecting to Grand Central), each splitting into two platform tracks facing the same platform; the six platforms would each be 15 meters wide, but unlike Les Halles, each of six access points would have six escalators, four up and two down in the morning peak, or alternatively four escalators and a wide staircase (the climb is 13 meters, equivalent to a five-floor walkup). There would be ample capacity for anything; emptying a full 12-car train would take forty seconds, and it’s unlikely an entire 12-car train would empty.


  1. Jim Shilliday

    “passengers arrive at the station uniformly but leave in clumps when the train arrives” — This is true if you mean the station, but not necessarily true if you mean the platform. At some busy stations such as New York Penn and 30th St. Philadelphia (Amtrak but not SEPTA), passengers are subjected to additional (and very unpleasant) queuing. Tickets are given a cursory check before passengers are allowed to descend to the platform a few minutes before the train departs — so passengers arrive at the platform in one clump after standing in line at the head of the stairs. I don’t know how this affects your analysis, but one effect of this procedure is to force all departing passengers to use one stairway, effectively taking all the others out of service. I have no idea what purpose this serves (other than to keep a few absent-minded passengers off the wrong train) — I suspect it’s security theater.

    • Untangled

      Well then let’s hope the next gen Metrocard is integrated with commuter rail. As for security, if you want to see security, go visit the metro systems in China or India.

  2. Henry

    I’ve always been of the mind that they should gut the escalators in Penn entirely and replace them with wider stairwells. Penn’s platforms are not that deep, and stairs are more space-efficient.

  3. Michael James

    The article by Louis Sato and Philippe Essig (March 2000) is fascinating. One notes that the French team visited Tokyo in 1971 and their plan for the RER interchange stations incorporating what they had learned was submitted early-1972 and approved in July 1972; and lines A and B opened in 1977. Simply inconceivable in today’s world, especially in the Anglosphere. (I guess I should mention that these were finalisations, that were increasingly urgent as the actual RER lines were being constructed, from the RER masterplan dating to 1965 which had been signed off by de Gaulle–weirdly almost seems like pre-history!)

    Concerning your points about the Chatelet-Les Halles station platforms, I found this in Sato & Essig:

    In 1970, access to the Paris metro platforms was controlled by automatic gates that closed when a subway train entered the station. The gates could also be controlled in the case of unexpected events to prevent large crowds building up on platforms. In this case, passengers were held back in the subway approach corridors.
    Despite the huge size of the RER project at Châtelet (Les Halles) Station (where a 17-m wide platform was planned), there were fears that a sudden surge of passengers onto the platform could not be managed and that safety would be a problem.

    Those “automatic gates” are what I think of as cattle controls: I can’t recall any at Chatelet but they still exist on some of the older Metro stations though one hardly ever sees them in action (but then I hardly ever used the Metro at peak times). And the size of the crowds today (line A with its 300m pax pa!) would boggle the minds of those original planners. Anyway, this worry about surging crowds has surely been solved (more than a decade after Sato & Essig) by the platform-aligned doors (at least for RER-A; ?RER-B at Chatelet?) so presumably they could build those extra escalators in the middle of the platform. I would have thought they would go for travelator-type escalators rather than step-type to more smoothly handle large crowds? Especially as the extra length required is easily accommodated by the very long RER platforms.

    I think it is also worth pointing out that Philippe Essig is one of those “elite” graduates of the Grand Ecoles who mixes engineering with business management and political life: he was State Secretary for Housing in the first government of Prime Minister M. Rocard as well as being at different times MD of RATP and of TransManche Link. Something we never see in the Anglosphere where we have total amateurs making such decisions (or of course in the current US administration even worse, people chosen for their antipathy to the normal function of their portfolios.)

    • Alon Levy

      A travelator has more capacity than an escalator per unit of width, but it has less capacity per unit of footprint area. The extra length required means that if you’re going up a level, a travelator takes as much space as multiple escalator banks.

      • johndmuller

        This seems to be a good spot to mention Ramps which while possibly suffering from that same footprint problem versus stairs as do the travelators versus escalators, nevertheless offer advantages to both the physically impaired and at the same time the physically adroit (who might choose to run in greater safety than on stairs).

        Grand Central Terminal in NYC makes extensive use of ramps providing both track access and vertical flow between levels in the common public areas as well.

        Yea Ramps.

        • Michael James

          The point about travelators versus escalators at Chatelet-les-Halles is as I wrote:

          Especially as the extra length required is easily accommodated by the very long RER platforms.

          RER platforms are extremely long and fitting in whatever is required is not the issue. There would be no compromises involved. The very reason I mention it is that most of us have been frustrated at the shambling shuffling pedestrian traffic jam at the bottom of escalators, sometimes to the point of taking the stairs instead. I seem to recall many TGV stations, including Eurostar, use travelators (though perhaps that is to help with luggage and trolleys?).

          • Alon Levy

            You’re still talking about one bank of travelators with an 8-degree angle versus three or four banks of escalators with a 30-degree angle. The RER platforms are long, but the ridership evidently fills them.

          • Michael James

            Alon, Yeah, but they aren’t going to put in three or four banks of escalators. And I’m sure they could fit in two banks of travelators on those platforms …. Also, travelators provide wheelchair access.

          • Alon Levy

            There are, if I remember correctly, ten sets of two escalators, one up and one down, per RER A/B platform at Les Halles. And there are elevators for wheelchair access, just no level boarding in SNCF territory because the platforms have different heights (1100 mm RATP, 920 mm SNCF, with some other SNCF stations at 550 mm because SNCF hates you).

        • Joel S.

          johndmuller – Ramps have many other additional benefits over escalators: they don’t break down; they don’t require a redundant elevator for wheelchair access; they have lower recurring maintenance costs; they don’t require a maintenance contract; they require no electricity to operate; they continue to operate during a power failure; they have no pinch points to injure travelers; and they are easier to negotiate for those travelers with luggage, bikes, baby strollers, and carts.

          Ramps are probably difficult to retrofit into existing stations, but once installed they require little to keep up. GO RAMPS!

  4. wanderer

    Speaking of vertical circulation, my walking but disabled wife and I are planning to visit New York next spring. It’s disheartening how few of the subway stations are disabled accessible. A lot of destination stations in Midtown are accessible, but the origin stations aren’t. I know that New York says that it’s a problem because the system is large and old, but other large, old systems like Berlin seem to be tackling it.

    • Alon Levy

      Berlin is pretty good about it, and Boston is very good on the subway (not so much on light rail or commuter rail). Paris is the single worst of the major developed-world systems – nothing is accessible except M14 and the RER.

      • Michael James

        Alon wrote:

        Paris is the single worst of the major developed-world systems – nothing is accessible except M14 and the RER.

        No accident that M14 and RER are the only newly constructed lines since 40 years. But Alon, how about the newly extended bits of old lines? I used the M7 “new” (in the 80s) extension into the suburbs (the three Villejuif stations) for about 5 years (more than 25 years ago now!) but I can’t exactly remember. I am sure there are escalators but only vaguely recall elevators? How about Mairie-de-Montrouge, the terminus of M4, which is the most recently constructed Metro station. On the surface I can only see escalators. I’ve spent 10 minutes on google and wiki and can’t resolve it. The RATP page on accessibility just returns a 404.

        But other things I found: M1, M2 & M13 are apparently fully accessible (no, I don’t know what it means). While not all buses have ramps, now every single bus route has some buses with them.
        I agree that one would have thought they could have made more progress in the last 40 years or so since when handicap access has been implemented in the developed world. But here’s my logic. First, all older metro systems have trouble with this and Paris has one of the most physically constrained city environments (where every bit of surface is accounted for and a good bit of it is heritage listed. (I’m wondering how they do it for M1. Is it perhaps those stair-climber devices rather than fitting new elevators?) Second, apparently two-thirds of the 300+ Metro stations have escalators and they may consider this provides access to those in wheelchairs though I suppose one might need an able-bodied helper? Third, given the dense bus coverage combined with RER access, it does actually make all of Paris accessible even to those in the banlieu. Perhaps not quite the convenience of the Metro but … Fourth, they may have taken the approach that to provide some patchy access at only some stations on some lines is a bigger safety issue than providing none. And equally, why complete lines are now getting done (and presumably simultaneous with the major refurb of M1).

        • Alon Levy

          1. The new extensions are not accessible, no. And no, M1 and M2 are not accessible; at Nation, the elevator only leads to the RER platforms, not the Metro platforms.

          2. If Boston managed to make stations in Downtown Boston accessible, Paris, where the cost of retrofits is the same as in Boston and ridership per station is much higher, has no excuse. Berlin is 50% accessible, New York is 20% accessible (bad, but better than Paris), London is adding accessibility at a decent rate. Paris is literally the worst here and instead of making excuses the way the New Yorkers do when I point out their construction costs, it should invest money in accessibility. Gutting M18 would produce enough money to get it a large part of the way there.

          3. Escalators are not accessibility. Washington tried that when it built the Metro, and it turned into a farce. Everywhere in the world, including in the opinions of Paris’s disability rights community, step-free access means elevators and not escalators.

          4. “Some wheelchair-accessible buses per route” would be illegal in the United States and Canada for new purchases; instead, the North American practice is that every bus should be accessible. Hell, even telling Metro users to take any bus is criminal given how slow Parisian buses are.

          • Michael James

            I think Boston is the clue to the problem: it really needs to be all or nothing. You pointed out in your other article that “London prohibited wheelchairs on the Underground until 1993 for reasons of fire safety”. With 300 stations in Paris it is a major job and I suppose they will do it in one big orgy one of these days, though it is curious if new ones like Mairie-de-Montrouge are not equipped. Perhaps they have provision but not fitted as they wouldn’t want to allow disabled to get on a metro and then get trapped down the line.

            It is ridiculous that I couldn’t find the information online (the top 5 google search results all promised info but were dead-ends) but I found it in a book I have (Discover Paris by Metro, an official publication of RATP + Mairie de Paris): there are a total of 15 accessible stations, the 9 of M14 and two of M1 at La Defense, and 4 at the end of both northern branches of M13. I suppose one can understand the La Defense ones but not clear why the M13 ones. (Also I can’t tell but assume from your comment that one cannot get from M1 to M14+RER-ABD at Chatelet, or M14+A+D at Gare de Lyon? For that matter I don’t know if M14 connects the disabled to those RER platforms at St Lazare, Chatelet, Lyon, Biblio Mitterand? I assume so.)
            Of course there are elevators at some other stations (eg. M4 at Cité) but I guess there are still other barriers to accessibility to get to the platforms etc, plus they don’t want to allow the disabled to get trapped in the system.

            Incidentally, while not excusing Paris-Metro, I think your comparisons are a tad misleading. Afterall with just the RER there are 33 stations within Paris that are accessible; with the Metro 15 that makes 48 so not much different to Boston’s 53! In fact considering all of greater Paris, at minimum (256+15)/560 = 48% of the rapid transit stations are accessible; and that is a lot of Franciliens! That is a fairer comparison.

            On your point 4, I assume all new bus purchases would be wheelchair compliant so it is just a matter of time before all buses will be compliant.

          • michaelrjames

            I think this report today confirms what I wrote in my posts, ie. best to be “all or nothing”:

            The Economic Toll of New York’s Inaccessible Subway
            If you can’t do stairs, half the city’s neighborhoods are transit deserts, according to a new report.
            By Claire Tran, August 4, 2018
            When Monica Bartley got off the New York City subway at Union Square, she found the station didn’t have an elevator for her wheelchair. So she took the 4 train all the way uptown to Grand Central Station, 28 blocks away, where she knew there’d be an elevator.
            It was broken. So Bartley was stuck underground for hours trying to head to work. Finally, she circled back to the station where she started, took the elevator up to the street, and took the bus instead.

            I’d also comment that I reckon there is a certain apocryphal aspect to this story. If Monica works in NYC then I think she would have sussed this out ages ago, and she wouldn’t have knowingly taken a train to Grand Central which is 28 blocks away from her workplace! But ok, all journos do that kind of thing, to make a point.

            Incidentally, talking about accessibility, your article of 2017 in Metro Report is no longer …. accessible!

          • Alon Levy

            Yeah, Railway Gazette and Metro Report put stuff behind paywalls after a while. I have to keep changing links in my database when they rot or become inaccessible; thankfully, RG and MR information that is unwalled is very high-quality so it’s easier to know what numbers to look for. (In contrast, Railway-Technology has a tendency to report old numbers and ignore cost overruns.)

          • michaelrjames

            Oops. Naturally the second after I submitted that comment I immediately notice that the Claire Tran article is from 2018! I might even have a comment to it, but of course Bloomberg have binned all that legacy (all those comments disappeared “like tears in rain” …). This is how Bloomberg are “hiding” their considerably reduced output in CityLab, by recycling old articles.

      • Matthew

        Slightly unfair to Boston light rail. After all they shut down Government Center for two years to rebuild it for accessibility (Green / Blue).

        Of the underground gated Green Light light rail stations, there are two remaining to rebuild: Hynes Convention Center (serving 3 branches) and Symphony (serving 1 branch). Hynes is going to be renovated by a developer of the air rights next to it – sorted. Symphony has dragged the most being rather constrained and somewhat lesser used. The city rebuilt the sidewalks a few years ago for accessibility purposes. Now the station is undergoing a design process to finish the job. So they’re getting there.

        Aboveground stations are a different story, it’s true. All of the new rebuilds have 8-inch platforms intended to interface with low-floor trolleys. And nearby manually-operated lifts just in case a high-floor has to be served (hopefully not). But there’s still a lot of legacy to be rebuilt. For example, somehow the city of Boston bastards in the early 1990s got away with rebuilding the outer portion of Comm Ave in Brighton without fixing the stations. Typical motorist garbage — make big wide speedy car lanes and don’t do a damn thing about the absolutely horrible conditions for the trolley stations. And I do mean horrible: 2-foot-wide platforms squeezed between moving trains and moving automobiles. Gotta be skinny to ride out there. Sigh. Anyway, since then the MBTA has been forced to rebuild such street-level stations and the city generally cannot escape from that obligation by pretending not to touch them when doing a street reconstruction. We’re getting two more done on Comm Ave over the course of this and next year. But let’s not talk about the outer end of the Heath Street line, where it runs in the street…

        The MBTA has had really shit luck with low-floor trolleys while the high-floor ones keep on trucking. The Breda ones were lemons and had to be beaten into some semblance of working order. But they have agreed to always run a low-floor train in every consist of more than 1 car, and it seems to have panned out for the most part. Sadly as a result, the new ones they ordered will have to replace the failing Bredas on-their-last-legs first before they can finally replace the high-floor but reliable Kinki Sharyo model.

        Assuming the bad luck bug doesn’t strike again… American railcar-order syndrome.

    • po8crg

      Even London is tackling it. Adjusting platform heights for level boarding and adding in lifts (elevators) where they can alongside stairs or escalators. Many London stations were originally lift-only and had stairs or escalators added to aid circulation, so in some cases there were unused lift-shafts to reopen, but in others the stairs were run through the old lift-shaft, so entirely new shafts have to be sunk.

      Stations need a major refurbishment every so often anyway (every 40-50 years or so), and adding lifts as part of that exercise makes sense.

  5. EfficientAG

    Great as always. Any thoughts on construction costs as it relates to vertical circulation? I wonder about the cost impacts of digging vertical versus slanted shafts, and if its worth improving elevator or funicular tech if either shaft design is preferable. Is there any mechanized system of large shaft boring, like turning a TBM on an angle?

  6. rational plan

    In London a lot of the accessibility programme is piggy backed on the station rebuild programme for increased capacity. It’s only seems a slight increase in budget when adding new escalator shafts and ticket halls to existing stations. Of course the Crossrail project has added accessibility to all intersecting lines to the new crossrail stations, plus all the existing suburban stations it now covers.
    The Underground now produces an accessbility map that acessible to platform and wheher that includes level boarding as well.

    Many suburban station are accessible to platform by accidents of history.

    With such a big old system there could be several strategy’s. Surface stations are cheap to convert, if not highly used. But converting sections of outer London lines would allow journeys to be taken in parts of the capital. Far more useful than the occasional station pairs linked together. On the other hand big interchange stations allow mutilpe line journeys to be taken and are important central city desitnations.

    The problem of course comes down to money. So in London I expect it will be a mix of pure accesibility projects at cheaper stations, and bigger stations coverved by other projects.

    For example the big new Piccadilly automation project will see trains go from 24tph to 36 tph. It will also see platform screen doors and level platform access and no more mind the gap. It won’t add any new lifts though, but you might see pressur for some to be added to key stations on such a big project.

    The government also runs an accesbility station grant programme, but it’s only a few hundred milllion a year and with strong competition for the cash.

  7. EJ

    It’s interesting that ReThinkNYC’s proposal for Penn station is entirely concerned with operations and passenger circulation (which is the important part) and their architectural proposal is more or less “whatever, just make sure all the platforms are accessible from Moynihan.”

    • Alon Levy

      Yep. That said, ReThink still has some magic asterisks in the plan, including the tunnel direction. The East River Tunnels today go, north to south, WB-EB-WB-EB, and ReThink wants to flip that to WB-WB-EB-EB, which is both difficult and pointless.

      • EJ

        Seems like it’s needed for their plan to 4-track the whole line from Penn to the Bronx. The one thing I don’t like is getting rid of the Empire connection and adding a long pointless trip through queens for every Amtrak train going up the Hudson.

        • Alon Levy

          It’s not needed at all – there’s already a flyover at the tunnel portal switching from WB-EB-WB-EB in the tunnels to WB-WB-EB-EB on the LIRR Main Line.

  8. FlavaNation

    For Penn Station, extending the Central Concourse to cover all of the NJ Transit tracks would help enormously. I remember this was discussed a few years ago. Currently the Central Concourse only covers tracks 13-21. The following website has the best diagrams of all the levels in Penn Station. It’s out of date since it doesn’t show the west end extension, but everything else appears accurate:

    This really underscores how much better LIRR customers have it than NJ Transit, as LIRR has access to four corridors, while NJ Transit has access to 3 (minus tracks 1-4, so maybe more like 2.5 corridors?). The technical problems for accessing tracks 1-4 from the west side concourse have been documented, but I’m wondering if extending the Central corridor has similar technical issues. Maybe once NJ Transit gets their financial ship improved then they could fund such an improvement, though it may be a hard sell politically for NJ to pay for a project in NY State.

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