Monthly Archives: September 2010

A matter of language – defining congestion and sprawl

LA the405

CC - by Atwater Village Newbie

Ahh, the power of creeping bias in language (hat tip to Jarrett Walker):

Everyone at the City should strive to make the transportation systems operate as efficiently as possible. However, we must be careful how we use efficient because that word is frequently confused with the word faster. Typically, efficiency issues are raised when dealing with motor vehicles operating at slow speeds. The assumption is that if changes were made that increase the speeds of the motor vehicles, then efficiency rises. However, this assumption is highly debatable. For example, high motor vehicle speeds lead to urban sprawl, motor vehicle dependence, and high resource use (land, metal, rubber, etc) which reduces efficiency. Motor vehicles burn the least fuel at about 30 miles per hour; speeds above this result in inefficiencies. In urban areas, accelerating and decelerating from stopped conditions to high speeds results in inefficiencies when compared to slow and steady speeds. The there also are efficiency debates about people’s travel time and other issues as well. Therefore, be careful how you use the word efficient at the City. If you really mean faster then say faster. Do not assume that faster is necessarily more efficient. Similarly, if you mean slower, then say slower.

Of course, biased language can be very useful when advocating for a certain point of view.  The real challenge is in sifting through biased language that poses as an objective statement.

Along those lines, Streetsblog notes how various congestion metrics, posing as an unbiased measure of the inadequacy of our transportation infrastructure, are actually misleading in terms of the impacts on our commutes and our land use choices.  They look at a recent report from CEOs for Cities:

The key flaw is a measurement called the Travel Time Index. That’s the ratio of average travel times at peak hours to the average time if roads were freely flowing. In other words, the TTI measures how fast a given trip goes; it doesn’t measure whether that trip is long or short to begin with.

Relying on the TTI suggests that more sprawl and more highways solve congestion, when in fact it just makes commutes longer. Instead, suggests CEOs for Cities, more compact development is often the more effective — and more affordable — solution.

Take the Chicago and Charlotte metro areas. Chicagoland has the second worst TTI in the country, after Los Angeles. Charlotte is about average. But in fact, Chicago-area drivers spend more than 15 minutes less traveling each day, because the average trip is 5.5 miles shorter than in Charlotte. Charlotte only looks better because on average, its drivers travel closer to the hypothetical free-flowing speed.

The Streetsblog Network chimes in, as well:

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.