Radial Metro Networks for Portions of Cities

I’ve harped about the necessity of radial metro networks, looking much like the following schematic:

However, in practice such pure radial networks are rare. Some networks have parallel lines (such as Paris and Beijing), nearly all have lines intersecting without a transfer at least once (the largest that doesn’t is Mexico City), some have chordal lines and not just radial or circular lines, and nearly all have lines that meet twice. Often these variations from pure radii are the result of poor planning or a street network that makes a pure radial system infeasible, but there are specific situations in which it’s reasonable for lines to meet multiple times (or sometimes even be parallel). These come from the need to built an optimal network not just for the whole city but also notable portions of it.

The unsegmented city

The diagram depicted above is a city with a single center and no obvious sub-areas with large internal travel demand. If the city is on a river, it’s not obvious from the subway map where the river passes, and it’s unlikely its non-CBD bank has a strong identity like that of the Left Bank of Paris, South London, or Brooklyn and Queens.

Among the largest metro networks in the world, the one most akin to the diagram above is Moscow. It has seven radial lines through city center (numbered 1-10, omitting the one-sided 4, the circular 5, and the yet-incomplete 8). They have some missed connections between them (3/6, 3/7, 6/9), and one pair of near-parallel lines (2/10, meeting only at Line 10’s southern terminus), but no parallel lines, and no case in which two lines cross twice. And Moscow’s development is indeed oriented toward connecting outlying areas with city center. Connections between areas outside the center are supposed to use the circular lines (5 and 14, with 11 under construction).

In a relatively monocentric city, this is fine. Even if this city is on the river, which Moscow is, it doesn’t matter too much if two neighborhoods are on the same side of the river when planning the network. Even in polycentric cities, this is fine if the sub-centers get connections via circular lines or the odd chordal line (as will eventually happen when Los Angeles builds a real subway network with such chords as Vermont and Sepulveda).

The segmented city

London and Paris are both segmented by their rivers, and their wrong sides (South London, Left Bank) both have strong regional identities, as does to some extent East London. New York, partitioned into boroughs by much wider waterways than the Thames and Seine, has even stronger sub-identities, especially in Brooklyn. I do not know of a single New Yorker whose commute to work or school involves crossing a bridge over a river on foot, nor of any case of anyone crossing a bridge in New York on foot (or bike) except for recreational purposes; in Paris I do so habitually when visiting the Latin Quarter, and at a conference in 2010 another attendee biked from Porte de Vincennes to Jussieu every day.

With a difficult water boundary, the wrong-side part of the city became a center in its own right. Downtown Brooklyn and the Latin Quarter should both be viewed as sub-centers that failed to become CBDs. The Latin Quarter, the oldest part of Paris outside the Ile de la Cite, declined in favor of the more commercial Right Bank as the city grew in the High and Late Middle Ages; Downtown Brooklyn declined in favor of more concentration in Manhattan and more dispersion to other centers (often in Queens) over the course of the 20th century.

Early 20th century New York and Paris were not polycentric cities. There was no everywhere-to-everywhere demand. There was demand specifically for travel within Brooklyn and within the Left Bank. To this day, the connections to the Latin Quarter from Right Bank neighborhoods not on Line 4 are not great, and from Nation specifically the alternatives are a three-seat ride and a long interchange at Chatelet. Ultimately, this situation occurs when you have a region with a strong identity and strong demand for internal travel larger than a neighborhood (which can be served by a few subway stops on a single line) but smaller than an entire city.

In this case, a radial subway network (which neither the New York City Subway nor the Paris Metro is) could justifiably have multiple crossings between two lines, ensuring that lines provide a coherent network for internal travel. South London is a partial example of this principle: not counting the Wimbledon branch of the District line, the South London Underground network is internally connected, and the best route between any two South London stations stays within South London. In particular, the Victoria and Northern lines cross twice, once at Stockwell and once at Euston, in a city that has a generally radial metro system.

Don’t go overboard

The need to serve internal travel within portions of a city is real, and it’s worthwhile to plan metro networks accordingly. But at the same time, it’s easy to go overboard and plan lines that serve only travel within such portions. Most of the examples I give of weak chordal lines – the G train in New York, Line 10 and the RER C in Paris, Line 6 in Shanghai – serve internal demand to the wrong side of a city divided by a river; only Shanghai’s Line 3 is an exception to this pattern, as a weak chordal line that doesn’t come from city segmentation.

In the cases of the G and M10, the problem is partly that the lines have compromises weakening them as radials. The G has too many missed connections to radial lines, including the J/Z and the entire Atlantic-Pacific complex; M10 terminates at Austerlitz instead of extending east to the library, which is the second busiest Left Bank Metro stop (after Montparnasse) and which has a particularly strong connection to the universities in the Latin Quarter.

But Line 6 is constrained because it doesn’t serve Lujiazui, just Century Avenue, and the RER C does serve the library but has exceptionally poor connections to the CBD and other Right Bank destinations. It’s important to ensure the network is coherent enough to serve internal demand to a large segment of the city but also to serve travel demand to the rest of the city well.

Good transfers

Serving the entire city hinges on good transfers. The most important destination remains city center, so lines that aren’t circumferential should still aim to serve the center in nearly all cases. Internal demand should be served with strategic transfers, which may involve two lines crossing multiple times, once in or near city center and once on the wrong side of the river.

The main drawback of multiple crossings is that they are less efficient than a pure radial network with a single city center crossing between each pair of lines, provided the only distinguished part of the city is the center. Once internal travel to a geographic or demographic segment is taken into account, there are good reasons to slightly reduce the efficiency of the CBD-bound network if it drastically raises the efficiency of the secondary center-bound network. While demographic trends may come and go (will Flushing still be an unassimilated Chinese neighborhood in 50 years?), geographic constraints do not, and place identities like “Left Bank” and “Brooklyn” remain stable.

Note the qualifiers: since the CBD remains more important than any secondary center, it’s only acceptable to reduce CBD-bound efficiency if the gain in secondary center-bound efficiency is disproportionate. This is why I propose making sure there are good transfers within the particular portion of the city, even at the cost of making the radial network less perfect: this would still avoid missed connections, a far worse problem than having too many transfer points.

So what?

In New York, London, and Paris, the best that can be done is small tweaks. However, there exist smaller or less developed cities that can reshape their transit networks, and since cities tend to form on rivers and bays, segmentation is common. Boston has at least two distinguished wrong-side segments: East Boston (including Chelsea and Revere) and Greater Cambridge. East Boston can naturally funnel transit through Maverick, but in Greater Cambridge there will soon be two separate subway spines, the Red and Green Lines, and it would be worthwhile to drag a rail connection between them. This is why I support investing in rail on the Grand Junction, turning it into a low-radius circular regional rail line together with the North-South Rail Link: it would efficiently connect the Green Line Extension with Kendall.

More examples of segmented cities include the Bay Area (where the wrong-side segment is the East Bay), Istanbul (where Europe and Asia have separate metro networks, connected only by Marmaray), Stockholm (where Södermalm and Söderort are separated by a wide channel from the rest of the city, and Kungsholmen is also somewhat distinguished), and Washington (where the wrong side is Virginia). In all of these there are various compromises on metro network planning coming from the city segmentation. Stockholm’s solution – making both the Red and Green Lines serve Slussen – is by far the best, and the Bay Area could almost do the same if BART were connected slightly differently around Downtown Oakland. But in all cases, there are compromises.

1. FDW

By “slightly differently” do you mean undoing the Oakland Wye as I’ve proposed, Or do you have another idea?

2. Untangled

Now that you talk about this, I can’t help but wonder what the centre of Berlin is? Is it around Alexanderplatz? But Friedrichstrasse seems very strong too…

• Milan

The official Nahverkehrsplan (https://www.berlin.de/senuvk/verkehr/politik_planung/oepnv/nahverkehrsplan/de/downloads.shtml) defines the two main centres to be the area around Zoologischer Garten and Kurfürstendamm and the area between Friedrichstraße and Alexanderplatz. Both are connected by the Stadtbahn and U2 (which also passes through the Potsdamer Platz area) and have their own small radial U-Bahn subnet around them (west with U1, 2, 3 and 9 + 4 and 7 nearby, east with U2, 5 and 8); the east also has various MetroTram lines, with frequencies between 4 and 10 minutes, passing through and ending at Alexanderplatz.

3. W.R.

You did not mention southern New Jersey, which is definitely segmented from Philadelphia. This, combined with the inherent bias of New Jersey state government toward the higher population areas of northern New Jersey, has stunted direct, fixed guideway access to the City of Philadelphia.

• Eric

Well, there’s PATCO, which is much better than a SEPTA regional rail line (its Philadelphia counterpart). But the other NJ corridors don’t have much.

And when the state proposes something they either scream that it will cause Queensification of their bucolic suburbs, that no one will use it because Real Americans(tm) drive everywhere or it’s a Communist plot to sap and impurify all of their precious bodily fluids. They can sit in traffic.

4. Matthew

The Union Square branch of the Green Line Extension could, in the future, reach to Porter Square where it would connect with the Red Line and commuter rail. This would also have the advantage of relieving some burden from one of the busiest segments of the Red Line and Park Street station. Porter Square is probably not as ideal a connection point as Harvard or Davis Squares but it’s what’s geographically available.

I haven’t kept up with the latest ideas for Grand Junction but it seems to me that a Lechmere / GJ connection would be relatively awkward and questionable in value when most of Kendall Square is less than a mile’s walk way from Lechmere. A GJ connection with Sullivan Square seems more useful. Of course none of this will happen anyway since GJ isn’t happening, unless some strategic ‘clue’ reserve is unlocked and given to the MBTA, the FRA, the city of Cambridge and the Commonwealth of Massachusetts.

• newtonmarunner

I’m with you on the Grand Junction. My main complaint about using the Grand Junction for regional rail is the taking away service from places like West Station, Newton Corner, etc., where a lot of people from Allston/Brighton/Watertown will transfer. With the Regional Rail Urban Ring, Newton to Salem headways have to be 7.5/15 minutes peak/base whereas with the extra capacity from not doing the urban ring, the headways would be 5/10 minutes peak/base. Many from Allston/Brighton/Watertown/etc. will still have to transfer to regional rail, and 15 minute headways off-peak are an awfully steep transfer penalty.

My maps have a JP to Sullivan Sq. via Centre St./Longwood/Fenway/BU Bridge/Grand Junction tramway/subway circumferential line. This prunes a Green Line Branch while keeping some sort of urban ring.

• F-Line to Dudley

The junction at Brickbottom being built for the GLX project would be able to fling future revenue traffic to/from Lechmere OR to/from Sullivan the way it is being designed. The lead tracks for the storage yard are being built on the proper alignment for Sullivan, and since Union Sq. station is a stub-end with zero storage past the platforms (potential point in favor of completing the Porter extension) there’s a straight connecting flyover for deadheading trains to/from the yard. Ditto for any trains going in/out of service at Lechmere. If the Grand Junction were connected to the Green Line it would be off the Union branch in a flying duck-under junction underneath the McGrath Highway overpass, where there is ample room being left behind after GLX to graft it on.

You can then make the Urban Ring a complete north-half circuit by burying the B Line under the reservation–where tunneling would be cheap–from Blandford to BU Bridge and inserting a flying junction to new portals at St. Paul St. for continuing B service and at the hillside next to BU Bridge and the Mass Pike for accessing the GJ. Should you then construct the proposed Urban Ring spur route to Harvard via Allston, you’d be able to insert a wye track at that hillside portal for reaching the Harvard branch EITHER from the Kenmore or Lechmere/Sullivan directions. On the east end you’d bridge across the Mystic River after Sullivan/Assembly and continue bolted next to the Eastern Route until reaching the current Silver Line busway in Chelsea, where you’d re-use or modify the current Silver Line busway (either co-mingled with buses or changed fully over to LRT ROW) to complete the rest of the circuit.

Tons of service possibilities you can draw up for that reimagined network with the multi-directional junctions at Brickbottom and BU Bridge. While the south half of the Urban Ring has no extant ROW’s and may need to be BRT out of necessity, the north half is almost tailor-made for a souped-up Green Line network given the ease at which those bi-directional junctions can be set up (including the relative ease of the subway dig + 1-2 BU subway stations between Kenmore and BU Bridge). Definitely a lot more robust and elastic than any Regional Rail scheme through Kendall given the extreme traffic impacts mainline rail would have on the GJ’s numerous grade crossings for anything more frequent than a handful of daily Worcester redirects…and potential inability to electrify that line at all for 25 kV AC given the system-worst and physically unmodifiable height restriction at the Memorial Drive overpass.

• Untangled

The thing I don’t understand about the Green Line Extension in Boston is why it isn’t a Blue Line extension instead. Given that GLX will be grade separated with no street sections, surely it is better to build it as a real subway line that won’t mix with traffic at the other end of the line, not to mention the capacity benefits and other benefits that can come from not having to deal with MBTA’s archaic light rail operating practices. And you also get to build the Red-Blue link as part of this extension.

• F-Line to Dudley

GLX is flat-out easiest to construct as a straight-on extension off Lechmere, where doing it Blue would require constructing an additional 1 mile of subway under AFTER the as-designed Red-Blue Connector @ Charles/MGH that the state refuses to build. It also would’ve bound the state to doing the off-ROW tunneling between Union Square and the Medford Branch to get all stops on a single alignment, which proved infeasible on the first-round scoping studies. The branching is an easy solve for Green because they’re just matching the E line to Union and (tentatively D, but could change) to Medford on the very under-capacity north end of the line past Government Center. All platforms on the extension are also long enough to take 3-car trains (or 2 cars of the proposed longer, all- low-floor Type 10 replacement fleet).

Branching wouldn’t be an option at all for Blue, so they’d have to lump the cost of Union tunneling hell or high water along with the unique-to-Blue Charles-Lechmere tunneling. Given the cost control issues that plagued GLX just on the current ROW, that would’ve surely sunk the whole project lock, stock forever. Somerville has been waiting for this extension since literally 1945 (https://commons.wikimedia.org/wiki/File:1945_BERy_extensions_map.jpg), so getting it done at long last is paramount. Blue wouldn’t have been an optimal use of time or resources at all. It’s also a very awkward routing to have the route bend back on itself, as Somerville-Revere is much more a radial than thru-on-thru demand pattern. It would’ve been the system’s oddball on demand turnover aligned that way. However, if you do ever find a future heavy-rail fit you can easily convert the Medford ROW and stations to get absorbed by a future HRT line, keep extending it to Winchester/Woburn next to the Lowell Line, and simply free up Green for Union + the Urban Ring northwest- and northeast- quadrant LRT. Nothing’s precluded at the century-level; there just isn’t a better fit amongst currently available lines to hook it into than going Green.

• Untangled

So they went for the cheapest but most compromised option. This would have been one case where the more expensive option would be better. If it meant the Red-Blue Connector + Green (Blue) Line Extension cost \$3-3.5 billion instead of the current \$2.3 billion, that would have been quite acceptable, by US construction costs at least, considering the extra benefits.

• F-Line to Dudley

No, they did not go for the most compromised option by choosing icky-poo LRT over totes-awesomer HRT. The Green Line north end is far under-capacity, has ample capability to branch, and has ability whenever needed to escalate service levels independent of any west-end congestion by putting Government Center’s Brattle Loop into service for rush-hour short-turns (as they do today to dump Boston Garden crowds during game nights). The ridership projections consistently track with GL train capacity and headways, and trip destinations for those parts of Somerville and Medford have always most-closely matched Green because of the buses (and former subway-feeding streetcars) going into Lechmere.

Blue, to the degree it was even included in the 1970’s, 1990’s, and 2000’s studies, was always a non-preferred ‘placebo’ that never made it out of the first-tier study Alternatives screening. The tunneling cost chew of getting from Charles to Lechmere was always fatal to its chances, with the duplicated stops at Science Park and Lechmere adding too little net value to overcome the additional cost and the entire boomerang-shaped route being a rough fit for Somerville-originating transit trips. There was, until Blue had its platforms extended in the mid-2000’s for 6-car trains, also only an 8-seat cumulative difference between the capacity of a 4-car Blue consist and a 3-car Green consist…not nearly enough to overpower the cost difference or make HRT better on-spec. And had Blue even survived long enough–in its current 6-car incarnation–in the most recent late-2000’s study to matter…the cost blowout of uniting Union Square–a must-have for any build–with Medford as one contiguous line would’ve sunk it. Branching is not a do-no-harm option for Blue and would wreck headway management on it, so when branching was proved to be the only cost-feasible way to include Union then Green became the only feasible source line (though it was already leaning far, far in Green’s favor before the Union tunnel buzzkill made it the “official” last man standing).

There’s plenty of other useful places you can extend Blue off Charles that are a lot less awkward than trying to force-fit it to GLX on the boomerang route. The extant design of the Charles extension permits full choose-your-adventure capability afterwards. There’s also plenty of practical things you can do to the Green Line writ-large to make it work less FAIL as a system and make the congested west end mesh better with the uncongested north end. Though as noted throughout this thread the whole north end with its own storage yards and fully available service escalator at GC/Brattle Loop is a very different and far higher-upside proposition that can also integrate the multi-directional Urban Ring routes…so its utility doesn’t begin or end with GLX and is inclusive of a much larger universe of practical possibilities.

• Untangled

Given MBTA’s archaic light rail operating practices, I would call it “icky-poo”, I mean for starters there’s front door only boarding on LRT, wtf… Of course, the Green Line has capacity past Lechmere, it’s only a stone’s throw away from the CBD but there would be more capacity/seats if it was built as a Blue Line although capacity isn’t the benefit from building it as a subway.

Since you mentioned Science Park, I was actually thinking of skipping Science Park and going to Lechmere straight from Charles, which will help with the cost and avoid duplication. And you could build a relatively cheap and simple immersed tunnel under the river, again helping with the cost. It will create a route that looks like a Boomerang but so will the Green Line anyway so it’s not any more awkward. Also, I don’t know why the cost of building a Union Sq-Medford junction (a junction to “unite” the two branches) would be much more expensive with the subway option as you’re suggesting, they’ll both be at the same location near mainline tracks and on the surface, you’ll need to have a really over-engineered design for that to happen. As for headway management being wrecked by branching, I don’t know what frequencies you’re thinking of but frequencies of up to 24 trains per hour are quite easy for branched lines to handle on fairly normal non-state-of-the-art equipment. All these things really sound more like excuses (possibly politically influenced) than real barriers.

The Focus40 MBTA plan is not very ambitious with its plan for the Blue Line, so with that in mind, there’s really no lost opportunity with letting the Blue Line do the job of the extension. You could even get the Union Square branch to turn south after that station to get to the Hospital cluster with connections to other lines instead of another pure radial line to the cluster like Focus40. And who knows, maybe the extension could even go down to Mission Hill and the Orange Line slashing cross-regional travel time and reducing CBD congestion. There will be other possibilities for extending the Union Square branch as well, a Blue Line extension won’t close off other extensions and ideas.

• F-Line to Dudley

There is no front-door only boarding in the subway as those are all prepayment stations, and if you have been following the rollout of the AFC 2.0 farecard launch at all (https://www.mbta.com/projects/automated-fare-collection-20-afc-20) you would know that all-door boarding and payment is officially coming at all B, C, D, E surface stops and buses within 24 months. The “icky-poo” comment is irrelevant, as the new fare system will be a couple years in-service before GLX makes its inaugural run.

Second, I already explained that when all the scoping studies were done the Blue Line had not yet had its platforms expanded from 4 to 6 cars, so there was a fewer-than 10 seat difference in capacity between a 4-car Blue train and a 3-car Green train. Blue did not start running 6-car trains until 2005 when its expanded fleet arrived, and the decision to extend the platforms was made AFTER Blue had already been eliminated from any consideration as a GLX mode in 2000. You can’t rearrange history’s sequence of events to make that criticism valid.

Third, I already explained that Somerville has been oriented to the Green Line for the subway’s entire 119-year history because the buses and former streetcar lines that GLX augments/subsumes have always run to Lechmere and/or North Station. It does not matter what physical shape on a map the Green Line resembles because its service patterns are where Somerville/Medford are going and always have been going. Blue’s boomerang DOES matter because Eastie and Revere are NOT where they’re going or ever have majority-gone. The scoping studies showed this clearly, so yes it is empirically a more awkward fit for demand.

Fourth, please read the actual plans before claiming ignorance on the “united” Union-Medford option (http://greenlineextension.eot.state.ma.us/documents/beyondLechmere/MIS8-05-Chapter4.pdf#page=5). Union is not remotely close to Gilman Square; tall, tall Prospect Hill (https://goo.gl/maps/71CvAaK8wTx) stands right in-between them. It would’ve required 3000 ft. of tunneling straight through the base of the hill to get back on-alignment. The Brickbottom station at Washington St. would’ve had to be omitted at ridership loss for the extension since that whole area between Washington and Union is expected to blow up big once McGrath Highway is torn down for an urban boulevard. The Prospect Hill tunnel studied out as wretched bang-for-buck.

Fifth, I’m not going to explain the dynamics of HRT branching from ground zero because reading this very blog will give you more than enough education…but how exactly do you expect to load-balance the Blue Line through downtown with a 1-stop stub at Union that’s 3 miles and 5 stations shorter than the Medford Branch? If per the ridership projections every Medford train is carrying more than twice as many passengers than every Union train by the time it hits the downtown transfers, dwell times through the CBD transfer stations are going to be divergent enough that Blue cannot keep the same headway for every train on the schedule at rush. You will never be able to sustain a max mainline TPH because one branch will forever have to carry additional dwell padding through the CBD than the other; the difference in characteristics between branches (even if assuming Union is extended to Porter) is much too divergent to pound back to par with ops hacks. Keep in mind as well that Blue’s extreme geographical skew to the other side of the Harbor means “CBD” for Blue extends to Maverick for the Eastie bus transfers, as that stop has nearly identical ridership to Government Center and State. Blue is NOT a Red Line analogue at all for branching capability. Cumulative Red Line ridership from JFK-south (i.e. 2.5 miles from the CBD) is a near-match for Red mainline ridership in Cambridge 2.5 miles on the other side of the CBD (presently an insignificant +2000 boardings in favor of JFK-south, with historical growth generally keeping the ends see-sawing around par). Red has zero programmed difference in schedule times between Ashmont and Braintree for dwells, functionally zero difference in crowding between Ashmont and Braintree trains at the CBD stops, and no trending for the foreseeable decades likely to upset that balance. Blue will never be anywhere close to balance if it took up the GLX branches (even with Union extended to Porter). Keep in mind that this is not an issue with the Green Line where there are 4 existing branch schedules of differing properties to mix/match for dwell balance through the CBD, and the car supply + throttle-up at Government Ctr.’s Brattle Loop to even out all remaining kinks between north end at west end during peak load or service disruptions.

While I’m sure none of these facts will dissuade your intensity of belief in “icky poo” hottakes dictating that Blue must…be…so, you can’t argue that this extension wasn’t studied to death for more than half a century. It’s been scored, re-scored, re-re-scored…poked and prodded by umpteen official studies and god knows how many engineers…the studies digested, debated, and dismembered by every member of the public Transpo intelligensia pre- and post-Internet. And for all that’s still controversial about what they’re doing and what it’s costing them to do it, the consensus over what color line the extension should practically carry was settled decades ago by a whole lot of crunched math. You’re going to have to rely on much much deeper analysis than crayon drawings and hand-waving away documented-to-the-nines construction and ops demerits to disprove that whole analytical body of work in favor of one “Blue…because my reasons” take.

5. Harpo Jaeger

“I do not know of…any case of anyone crossing a bridge in New York on foot (or bike) except for recreational purposes”
Really? I used to bike from Brooklyn to Manhattan every day for work, and I’ll soon be doing it again. I would guess that many thousands of people use the Manhattan Bridge to commute to work every day, to say nothing of the Williamsburg Bridge.

• crazytrainmatt

While Alon’s point about NYC being divided by its rivers is taken, weekday bike traffic across the city east river bridges has been above 20,000/day for the last few years. I expect most of these are commuters and such rather than recreational cyclists. The Harlem River bridges are shorter spans but have had far worse pedestrian and cyclist environments, although DOT is making a push to improve things; regardless the 10 bridges get ~4,000 riders each per summer weekday. The MTA does its best to make cycling tough on its two bridges: the Triboro isn’t included in the east river counts and they enforce the ban on cycling every so often; the Henry Hudson path is closed for year and obnoxiously narrow next to an excess of travel lanes. Even the GWB gets 1,000 bikes per weekday in the summer despite the lousiness of the path.

This ridership is the fruit of several decades of advocacy to have dedicated paths and safe access routes, and is pretty high given the (still) hostile cycling environment compared to Paris or other European cities.

The G has too many missed connections to radial lines, including the J/Z

Some of the iterations of the IND “Second System”, I haven’t seen them all…. has a 6 track recreation of Hoyt-Schemerhorn perpendicular to the G at the Broadway station. If there going to be six tracks of subway under Broadway, connecting to the El isn’t a high priority. Assuming they weren’t plotting to tear down the El and turn the ROW over to more automobiles. Squint at the iterations the right way, they were planning on tearing down the El. Like they did on Fulton. They were plotting to tear down the Myrtle Ave. El too.

and the entire Atlantic-Pacific complex

It doesn’t go anywhere near it. It doesn’t have to, there’s other ways to get to the LIRR. You could and can change to the 4th Avenue lines at 4th Ave/9th Street and if the full blown extravaganza of six tracks of 2nd Ave and six tracks of 8th Ave had been built change to the Brighton line and the Nostrand Ave line at Bedford-Nostrand. On one hand you are arguing that mass transit should be spread out but want everything to go one place. Make up your mind.

I’m sorry you having trouble conceiving of things with more than three lines. Full blown Second System it would have connected to the Brighton, Nostrand and Utica lines at Broadway. Everything can’t go everywhere. Some people are going to have three seat rides. They can have three seat rides in systems with more than a few lines. The G train could go to Jamaica but never has, as I can tell. Or Coney Island. It doesn’t go to Wall Street, it doesn’t go to Times Square, it doesn’t go to Grand Central. Or the Rockaways or the Bronx. Or Staten Island or Boston or Chicago or Los Angeles either. …there is transportation that will take you from where you are to where you are going. It’s called an automobile.

7. Michael James

and the RER C does serve the library but has exceptionally poor connections to the CBD and other Right Bank destinations.

I’ve resisted nitpicking so far, but heck what is a blog for …?
“exceptionally poor”, really? I wouldn’t even say “poor”. Given the impossibility of the line being simultaneously on both sides of the river, RER-C does a rather good job of serving an awful lot of Paris, because it intersects with 9 Metro or RER lines (not counting the arm of RER-C1-C3 that does cross to rive-droite–if not in a very useful part–which intersects with 4 more Metro lines). Four of those rive-gauche connections provide 2-ride links to the CBD (5 if one counts RER-B to les-Halles). Possibly the best (for those coming from S+E suburbs) is M14 (Bibliotheque Nat.) because it is the first station inside Paris, and M14 is a fast line and goes thru the heart of rive-droite and several stops in the CBD. If coming from the W+S suburbs you’d have to wait to the 6th station inside Paris (Invalides) to transfer to M13 or M8 which gives you a wide choice of destination stations within the CBD and rive-droite.
Let me also point out that, while one always prefers to avoid 3-ride journeys, in Paris they are tolerable because of the density of the Metro and the very high frequency especially at peak times. I’d say this is not true for NYC or London (and in London your destination station may actually be quite a distance from your final destination).

But on your overall theme–as far as I understand it–wouldn’t it be more informative to compare city systems that were more or less designed in whole, ie. Paris (excepting the RER), Moscow maybe Madrid, not London or NYC. And I suppose Shanghai & Beijing. That is, systems that have been built and added to over long periods will have been subject to all kinds of forces outside the control of planners (political, budgetary, nimbyism etc).

• Alon Levy

Sure it can serve two sides of the river – the RER B does. All it would’ve taken was enough foresight to tunnel from Gare d’Orsay to Saint-Lazare rather than to Invalides.

The RER C indeed interchanges with many Metro lines, but the transfer corridors are long. Transferring from M8 at Invalides was possibly even worse than transferring between M1 and the RER at Chatelet. The Saint-Michel transfer looks even worse. M12 is a missed connection. So de facto the state of the connection to the CBD is very poor. Maybe M14 is better, but my trip is entirely intra muros then it’s not really relevant to me.

The Metro here was designed as a whole network, but this is only true of its first few lines (M1-6, and portions of M7 and M8). M10 was not designed together with the other lines, and it shows. And then the RER A and B were designed together, but the RER C was designed separately, and again it shows.

• Michael James

So you always say, but I think it is arguable. I look at it from the perspective of suburban commuters and RER-C serves them from east+south and west+south; this is its main raison d’etre. Thus it made perfect sense to complete the “missing link” along the river to create RER-C, and it was relatively cheap (compared to a deep tunnel Invalides to Saint-Lazare). Hence I also don’t think your perspective of exclusively intramuros Paris is valid. Of all the RER lines I would say your average Parisian would have least recourse to using RER-C as part of any intramuros journey. (Tourists on the other hand: St-Michel-Notre-Dame, Musée d’Orsay, Tour Eiffel and Versailles). Having said that, with its 9 intramuros stations along the banks of rive-gauche, it does fill in some gaps and interconnections left by the Metro network. Besides which, M14 is going to do a lot of what you want for a whole lot of southern banlieusians when it gets extended.

Also, I think you make too much of those correspondences. They work, and much better to have them than not to have them (especially in winter). Anyway it is as I said in my final para (previous post): the RER was not designed at the time of the Metro so it was not feasible (while technically possible, I suppose) to make all its connections perfect. And what I tried to ask, is whether those big-city systems that were designed and built as a whole, come any closer to your ideal?

8. AlternativeTransport

Doesn’t a radial and circumferential network for a city, with one existing downtown, damn the city to continuing being such a city? It robs the opportunity for the city to develop into polycentric city. It drains the outer boroughs and concentrates city infrastructure, jobs, wealth, culture in the centre. It forces residents to commute longer and makes the city as a whole less agile.

• Alon Levy

No, the fact that downtown is more desirable is what keeps cities strongly-centered. Paris has a Metro grid with parallel lines and several centers and somehow the job center remains in the same CBD, just slowly creeping west due to commercialization of rich areas.

• Alon Levy

Paris is plenty polycentric, it just has one center that’s far stronger than all the others. The same is true of Tokyo, London (with two centers), etc.

Take even Los Angeles, which has a bunch of sub-centers and not just Downtown. Downtown has 250,000 workers out of a total of 4 million in the county. But this is not because LA has 16 different job centers of which Downtown is one. Century City has 34,000 workers, UCLA and the VA Hospital together 28,000, LAX 50,000, El Segundo 52,000, Downtown Burbank 49,000. The vast majority of LA workers just work outside a big job center and drive because there is no way in hell transit is serving small job clusters unless they happen to be on the way between any two major ones, which few are. The situation in Paris is the opposite: there are multiple centers, but nearly everyone works in a high-job density area, while the CBD has a distinguished place even though the transit network serves Les Halles a lot better.

9. Shengxi Deng

Just so you know, this looks almost identical to Chengdu`s current + future metro lines before 2020.

10. Pingback: Little Things That Matter: Interchange Siting | Pedestrian Observations

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