Apparently I’m not the only one thinking about urban mismeasurement, because the planning blogosphere is lighting up with examples. In addition to my critique of per passenger-mile measurements and the aforelinked critique of average density (and the great follow-up post here), I’ve noticed two other discussions about mismeasurement in urban planning:
1. A report funded by the Rockefeller Foundation criticizes the standard measures of congestion used by the Texas Transportation Institute’s “industry standard” Urban Mobility Report. It cites the Travel Time Index in particular, or the ratio of average peak travel times to non-peak travel times (it’s unclear but I believe they’re only talking about cars), as being particular pro-sprawl, in that it rewards cities where it’s hard to get around to begin with. While measuring total time spent in peak hour traffic, apparently dense metro areas like Chicago, Portland, and Sacramento have the lowest peak travel times, with Nashville holding up the rear with the longest average time spent in rush-hour traffic.
This summer I worked in the air quality division of the metropolitan planning agency in Northeast Ohio — known as NOACA. NOACA is the local agency responsible for disbursing federal highway dollars. To a certain extent, its actions are governed by a series of federal directives.
While I was at NOACA, we hired an “air quality planner” whose main responsibility was to perform an analysis mandated by the feds to measure the air quality impacts of every proposed road project.
The problem was, the analysis inevitably concluded — without fail! — that expanding a road would reduce air pollution.
That’s because the formula only accounted for short-term air quality impacts. Any given road project was likely to reduce congestion in the short-term and provide an immediate reduction in vehicle emissions. But the formula ignored long-term impacts of highway expansion — sprawl, longer commutes — which run directly counter to the cause of air quality. The formula simply wasn’t sophisticated or far-sighted enough to account for this type of effect.
Unfortunately it looks like these short-sighted air quality studies are to some extent the result of lawsuits by environmental groups.