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Where's the Beef?

Or at least, the capacity?

The first strategy for adding additional housing outlined in Mayor Bloomberg's 2030 plan is to pursue transit oriented development. In simple terms, dense development around transit stations and hubs. However, the plan also describes capacity issues that our transit system faces today and will face in the future. So, we should build all our new housing clustered around a transit system already reaching capacity? Hrmmm...

Looking at subway ridership in a long term context, it's pretty clear however that while some lines may be quite crowded today, the system as a whole is substantially below the highest usage levels it has supported historically. On the whole, we have recovered from a nadir of 915 million trips in 1977 to 1.5 billion trips in 2006 -- about the same as in 1952.

We all know that commuters from Williamsburg and the Upper East Side are suffering, but the question remains -- are there parts of the city where subway usage is substantially below levels that have been supported in the past? Comparing each station's 2006 annual ridership to levels in 1952 yields the following map, where red indicates a net decrease over the last 54 years (and thus, theoretically, excess capacity):

This analysis of course doesn't account for the fact that bringing the South Bronx back to historical levels would make the problems on the Lexington line even worse than they are today, but it at least gives a sense of what areas could accept housing growth around subway stations if the most pressing line-level capacity issues were resolved.

What if we want to look at each station's or line segment's pattern over time? As they say here in London -- "watch this space" (and think sparklines).

[Technology Shoutout: most of the work for making the above map was done by the ever-more-brilliant open source PostGIS and GeoServer packages.]

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This page contains a single entry from the blog posted on July 30, 2007 12:57 PM.

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