{"id":244,"date":"2009-07-24T15:40:36","date_gmt":"2009-07-24T19:40:36","guid":{"rendered":"http:\/\/cityblock.wordpress.com\/?p=244"},"modified":"2009-07-24T15:40:36","modified_gmt":"2009-07-24T19:40:36","slug":"polycentricity","status":"publish","type":"post","link":"https:\/\/www.alexblock.net\/blog\/2009\/07\/24\/polycentricity\/","title":{"rendered":"Polycentricity"},"content":{"rendered":"
\"VRE<\/a>

VRE Train. Image from Ouij on Flickr.<\/p><\/div>\n

Nobody would argue with the idea that DC’s commuter rail system could be better.\u00a0 Metro, however, is largely praised (disaster responses and publicity notwithstanding<\/a>).\u00a0 However, Metro also gets attacked in some quarters for its hybrid nature as both an urban subway and a commuter rail system.<\/p>\n

Richard Layman in particular<\/a> likes to emphasize<\/a> the writings of Steve Belmont<\/a>.\u00a0 When talking of transportation, Belmont contrasts monocentric transit systems (essentially dense hub and spoke networks with all lines serving a dense core) with polycentric ones, where the city has many nodes and thus requires many links between them.\u00a0 Belmont (and Layman) argue that polycentric is bad and monocentric is good – at least at encouraging dense development and urban living within the core.\u00a0 The problem, however, is that the monocentric\/polycentric division isn’t all that useful when only comparing one system to another.<\/p>\n

Belmont’s two main criteria for determining the centricity of rail transit systems are station density and the spatial extent of the system.\u00a0 Metro in DC fails on both accounts, as it has long ‘tail’ lines and stations separated by long distances.\u00a0 However, within the core, the station density is actually quite high – extremely high when you consider the context and time it was built (as opposed to the older systems in New York et al with predominantly cut and cover construction).<\/p>\n

Paris, on the other hand, is the textbook case of monocentric rail transit, Belmont argues.\u00a0 Paris’s Metro has more line miles than DC’s Metro, but all of them are squeezed into an area no more than 7-8 miles in diameter.\u00a0 Likewise, there are far more stations within that smaller area.\u00a0 It’s an incredibly dense system.<\/p>\n

Where the comparison breaks down, however, is the limitation in comparing one system to another.\u00a0 DC’s Metro is a hybrid system and needs to be analyzed as such.\u00a0 To make it as close to an apples-to-apples comparison, you’d need to analyze a combined system of both Paris’s Metro<\/a> and RER<\/a>.<\/p>\n

Jarrett Walker did just that<\/a>.\u00a0 The end result is that Paris’s employment patterns are far more polycentric (and as Walker argues, more akin to Los Angeles rather than New York) than Belmont might imply. Walker’s starting point was Alon Levy’s proposal for through-running commuter rail trains in New York (Part 1<\/a>, Part 2<\/a>), a theme I picked up on with ideas for DC’s commuter rail<\/a> system.\u00a0 Walker writes:<\/p>\n

But when you start looking at the cost\/benefit of all the tunnelling to get the various commuter lines connected to each other, you stumble on an important difference between Paris and New York. \u00a0For all the suburbanization of the last 70-some years, New York still has an world-class concentration of jobs and activities in a very compact core (roughly the southern half of Manhattan plus inner Brooklyn). \u00a0For trips from the outer suburbs to this core, it’s not hard to get where you’re going with the existing commuter rail line and one connection to the subway.<\/p>\n

Paris commutes are widely distributed to major employment centers located mostly on the edges of the city. \u00a0This pattern particularly cries out for RER-style through-running of commuter rail because so many people are commuting to a center on the far side of the city from their origin — for example, from suburbs east of Paris to La D\u00e9fense in the west. \u00a0Greater New York would benefit from such an arrangement, but not nearly as much as Paris does. \u00a0For New York it’s a nice feature, but for Paris it’s foundational to the growth pattern of the city.<\/p><\/blockquote>\n

Polycentricity is the fundamental pattern for the region.\u00a0 This statement could apply just as easily to DC (especially in terms of employment clusters) as it does for Paris, which is why the through-running concept is so attractive.\u00a0 The Overhead Wire has some great images<\/a> talking about how we shape that polycentric reality that most cities deal with.<\/p>\n

Walker’s takeaway message is this:<\/p>\n

Los Angeles and Paris have come to their similar structures by very different paths, and have drastically different cultures of planning. \u00a0But urban structure is destiny<\/strong> because it changes so slowly and incrementally. \u00a0The constellation of major centers in both cities is a tremendous advantage for transit: people are flowing in all directions to centers on various edges of the city, so there is a huge area in which transit demand is two-way. \u00a0By contrast, suburban commuter service into New York will always be a story of trains and buses flowing empty or nearly empty in one direction so that they can run full in the other, because the concentration of jobs in the center is so massive.<\/p><\/blockquote>\n

I can’t think of a better vision for DC’s future – a dense core employment area, surrounded with high density neighborhoods – and other employment centers around that (Rockville, Bethesda, Silver Spring, Alexandria, etc).\u00a0 Enabling, where possible, DC’s commuter rail system to offer through-service to those centers would be a huge improvement in service for DC’s current (and future) economic geography.<\/p>\n","protected":false},"excerpt":{"rendered":"

Nobody would argue with the idea that DC’s commuter rail system could be better.\u00a0 Metro, however, is largely praised (disaster responses and publicity notwithstanding).\u00a0 However, Metro also gets attacked in some quarters for its hybrid nature as both an urban subway and a commuter rail system. Richard Layman in particular likes to emphasize the writings […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"jetpack_post_was_ever_published":false,"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":false,"jetpack_social_options":{"image_generator_settings":{"template":"highway","enabled":false},"version":2}},"categories":[8,46],"tags":[],"class_list":["post-244","post","type-post","status-publish","format-standard","hentry","category-commuter-rail","category-transit-oriented-development"],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"","jetpack_shortlink":"https:\/\/wp.me\/pHcGQ-3W","jetpack_sharing_enabled":true,"jetpack-related-posts":[],"_links":{"self":[{"href":"https:\/\/www.alexblock.net\/blog\/wp-json\/wp\/v2\/posts\/244","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.alexblock.net\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.alexblock.net\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.alexblock.net\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.alexblock.net\/blog\/wp-json\/wp\/v2\/comments?post=244"}],"version-history":[{"count":0,"href":"https:\/\/www.alexblock.net\/blog\/wp-json\/wp\/v2\/posts\/244\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.alexblock.net\/blog\/wp-json\/wp\/v2\/media?parent=244"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.alexblock.net\/blog\/wp-json\/wp\/v2\/categories?post=244"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.alexblock.net\/blog\/wp-json\/wp\/v2\/tags?post=244"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}