the economist and the “redundancy” fallacy

Today's unsigned piece in the Economist "Democracy in America" blog picks up on Tom Vanderbilt's Slate item reviewing my book.  I'm certainly grateful for the publicity, though for the record, I do believe in pleasure!

But the Economist's writer ends his piece with a commonplace of old-inner-city thinking that can do real harm when taken outside those bounds:

Ultimately, what makes public transit work is massive redundancy: lots of different systems layered on top of each other, all running at high frequencies, providing you clear information on when the next one arrives. The world's best cities, New York, Paris, London, Hong Kong, Berlin, all do this pretty well. For cities that aspire to greatness, the road map doesn't seem so hard to follow.

"Lots of different systems layered on top of each other" begs the question of whether these systems are working together — for example by encouraging connections from one to the other — or simply duplicating each other.  That is the distinction that matters.  

Yes, if you're in "New York, Paris, London, Hong Kong and Berlin" you may perceive a layering of "redundant" services, but one of two very different things is happening:

  1. The services are truly redundant in the sense of duplicating (or even competing) but the demand is so intense that they're all full, so the duplication isn't much of a waste.  This is the case with many big-city commute markets, but often not with all-day patterns.
  2. The services are actually fitting together into an integrated network, through some mix of planned connectivity and complementarity.  An example of complementarity is the simultaneous presence of services in one corridor that differ in the speed/access tradeoff.  A major Manhattan avenue, for example, may have an "express" train stopping only every mile or less, a "local" train stopping less than every half-mile, and a bus on the surface stopping even more frequently.  That isn't redundancy unless the market isn't strong enough to support all three.

Praising these super-dense cities for "massive redundancy" sends exactly the wrong message to less-dense and smaller cities.  Tell them to plan for redundancy, when their markets are insufficiently developed, and they'll spread their resources out in tangles of overlapping services none of which are frequent or attractive enough to be worth waiting for.  This is the lesson of inner Sydney, discussed in Chapter 12 of my book.

You need massive agglomeration for true redundancy to work.  Without that, you dissipate service quality too much.  This was a key failing of the privatization of the British bus industry, which gave private companies control over transit planning and prohibited them from working together to create rational connective networks, by declaring that to be collusion.  The result was a generation of frustrated riders who had to let Jim's bus go by because they had a ticket for Joe's bus, even though the two bus lines together might add up to enough frequency to actually be useful.  The last Labour government finally removed this prohibition on "collusion," allowing simple, obvious, and mutually beneficial plans to go forward, like this one in Oxford.

"Massive redundancy" may be fine if you're a megacity, though even there, its effectiveness may be a feature of the peak that doesn't translate to the rest of the day.  Anywhere else, services need to work together as a network.  Even in London, New York, Paris, Hong Kong and Berlin, that's really what's happening. 

8 Responses to the economist and the “redundancy” fallacy

  1. Alex B. January 24, 2012 at 6:55 am #

    This would also seem to speak to the integration of land use planning into the mix. If a city is rapidly growing and adding density as it builds, that’s an entirely different scenario than assuming the city is mostly static and the transportation planning should solve for that problem as if it were a simple equation.

  2. Erik G. January 24, 2012 at 1:34 pm #

    I’d leave Berlin out of these comparisons. Its transportation network is still distorted by the post-war division of the city until 20 years ago. Tons of cash thrown at it since then; Trams still really only in the former Soviet sector; S-bahn operated by three different entities in the West (DR, then BVG then S-Bahn Gmbh) in the past 30 years has altered things a bit.

  3. Tobias January 25, 2012 at 4:19 am #

    Berlin fits perfectly well in this list.
    Post-unification investments just bridged the gaps in the network and refurbished a couple of stations. The trams in the east complement the Underground which runs mainly in the west part of the city. And the S-Bahn just got its pre-war network restored. A network which was set up by a single entity, the DR.
    Berlin is nothing special anymore. Just another city with a decent public transport system.

  4. Stevevance January 25, 2012 at 11:01 am #

    The only signed pieces in The Economist are the columns and the blogs. Every standard news items is without an author.

  5. Erik G. January 25, 2012 at 11:27 am #

    Tobias, the post-1961 boycott and decline of the East German run S-Bahn in the western sectors influenced where the BVG U-bahn was extended in the 1970’s and 1980’s. (See U7 extension to Rathaus Spandau). And no city, apart from possibly Dubai, has ever seen so much money put into infrastructure in so short a time as Berlin did from 1990 until 2010. As it was, West Berlin as a shrinking city, was not needing any expansion of its rail transit network, except that monies were freely flowing from Bonn in order to present West Berlin as a showpiece to the DDR

  6. Miles Bader January 25, 2012 at 3:14 pm #

    BTW, another time when “massive redundancy” proves extremely useful is when something goes wrong—an accident that shuts down a line, inclement weather that’s harsh enough to cause problems, disaster, etc.
    Having multiple viable routes to get home is very comforting when a massive snowstorm has shut down half the city…

  7. TransitPlannerMunich January 30, 2012 at 1:32 pm #

    As someone living in Bavaria I do not love to defend Berlin, but I have to do it here… (as if a person from Texas would have to defend NYC)
    Berlin is definitely not a shrinking city. With currently 3.490 million inhabitants it has a bigger population than ever since 1944. Even more, the area around Berlin grew significantly.
    Berlin has a really good network – funny enough including the S-Bahn. And you need only one ticket for an area with 6 million people reaching until the border to Poland – with 1.2 billion public transit passengers annually.

  8. Philip September 27, 2012 at 7:05 am #

    A late comment, but the Berlin network is definitely not “redundant”. Over much of the city, there are deliberately no bus services running over the same routes as U-Bahn lines. Which can pose difficulties for people with poor mobility travelling to destinations on streets like Skalitzer Strasse or Karl-Marx-Allee, where there is no transport along the street with shorter stop spacing than the U-Bahn.