How Flawed Formulas Lead Down the Road to Sprawl

The new CEOs for Cities report on the misguided metrics that fuel sprawl is getting a lot of attention today on the Network and in local media.

Bike Portland and The Infrastructurist are both featuring the study, which found major flaws in a metric that’s widely used to justify road expansion. Several local press outlets ran stories about it under headlines like, “Sacramento traffic not so bad, really.”

As Noah reported yesterday, “Driven Apart” author Joe Cortright takes aim at the use of the Travel Time Index, a measurement that emphasizes traffic congestion while ignoring total travel time. The outcome is easy to predict: Calls to relieve congestion by widening roads, which leads to spread out development and longer car trips. But if we instead emphasized total travel time, Cortright shows, the way to achieve better commutes is to build more compactly.

In many places, expanding roads is the government's current answer to air pollution, as a result of perverse, antiquated air-quality formulas. Photo: ##http://www.pblaminations.com/##PB Laminations##

I’ve seen the same logic that underpins the Travel Time Index guide transportation policy decisions, and I wanted to share an example of how this undermines cities and sustainability at the local level.

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.

Yet transportation and planning agencies use this federal formula to guide highway construction decisions across the country. Looking at development patterns over the last several decades, I guess that shouldn’t be surprising.

So thank goodness for the CEOs for Cities report, pointing out the absurdity of an entrenched way of looking at how transportation works. Hopefully, this report reaches willing ears in Washington and in local governments. Just imagine all the ways those federal dollars might be put to better use actually reducing air pollution.

Elsewhere on the Network today: Rights of Way outlines a campaign to pressure the Maine Turnpike Authority to divert some of its revenues toward a successful commuter bus service rather than spend ten times that amount on a road widening. Publicola asks why Portland seems to edge out Seattle in the “cool” cities matchup (the answer has to do with sustainable infrastructure). And Grist chats with Congressman Earl Blumenauer about the Obama administration’s Sustainable Communities Initiative.

  • True Freedom

    We have to be careful not to replace one bad metric with another. Total travel time is equally flawed and will also lead to bad planning decisions. Why? Minutes spent traveling are not created equal. Traveling 30 minutes in stop and go congestion is worse than 30 minutes of free-flowing travel.

    We need to step back and think about what we are really trying to achieve, and create metrics that measure success towards that goal.

    Is the goal lower regional emissions? What about local emissions? These may conflict. We may be able to cut emissions in half by crunching people into one tenth the physical space. Regional emissions down by 50%, local emissions up by 250%. Is that the right tradeoff?

    VMT, especially per capita VMT, has similar problems. Not all miles are created equal. Additionally, I have seen planners use data that shows a doubling of density reduces VMT by 30%. Well, depending on the situation, you may now have twice as many people traveling 70%, which is still an increase of 40% local VMT over not increasing density at all.

    Is reducing emissions the only goal? Are we trying to limit sprawl for some other reason? Are we trying to improve travel efficiency, so that our society’s productivity increases?

    What we really need to do is enumerate the goals and their relative performance, and then develop metrics that really measure how we are delivering on these goals. So far, all the metrics I’ve seen will lead us to poor decisions.. at least with respect to limiting emissions.. especially local high concentrated emissions.

  • Joseph E

    “Traveling 30 minutes in stop and go congestion is worse than 30 minutes of free-flowing travel.”

    Traveling 30 minutes on a comfortable train or express bus, listening to music, reading a book, is even better. But how do you account for that?

    I would argue that riding a bike for 30 minutes, even with traffic and lights to deal with, is even more fun and healthy than riding the bus or train (and much better than driving), because you get exercise and get outdoors. But that’s my opinion.

    Total travel time per person seems the best statistic, but perhaps we should also survey people and find out how happy they are with their transportation options, in addition to measuring the length of time they spend traveling. I imagine the transit riders, bikers and pedestrians would be much more satisfied.

  • Al

    “Traveling 30 minutes in stop and go congestion is worse than 30 minutes of free-flowing travel.”

    Er, why? I mean, I get that it’s more irritating to the driver, but it doesn’t require any more time, it’s safer, it uses less fuel, and there’s lots of room for improvement with carpool lanes, rapid transit, etc. If you have free-flowing traffic, it can’t ever get any better, but it can get a lot worse (30 minutes of free traffic can turn into 90 minutes of stop and go over a few years, and then what can you do?)

    “you may now have twice as many people traveling 70%, which is still an increase of 40% local VMT over not increasing density at all.”

    Sure, if you measure VMT-per-block-of-land instead of VMT-per-person. But why in the world would you do that?

  • Mike

    Al – I don’t get your logic that “traveling 30 minutes in stop and go congestion is worse than 30 minutes of free-flowing travel” uses less fuel – since it’s more efficient to move at a steady pace (granted, 50 mph is more efficient than 70 mph) rather than repeatedly accelerate and brake.

    However, there is another reason that “traveling 30 minutes in stop and go congestion is worse than 30 minutes of free-flowing travel” may not necessarily be true – the former situation implies that you are traveling a much greater distance, utilizing more infrastructure (which is costly to build and maintain). If you’re going twice as fast in the same amount of time, you’re going twice as far. The infrastructure needed to support such dispersed travel patterns is much more expensive (and less efficient on a per-capita basis) than something that’s more densely used.

  • Thomas Le Ngo

    Mike, I think in your first paragraph, you meant that you *do* get Al’s logic, correct? I had to reread your post a couple times..

  • True Freedom

    Al – the reason you might want to have some local measure of VMT is because the effects on your lungs of air pollution are due to the local air immediately around you.. so making the trade-off to drastically increase local air pollution in order to gain fewer global emissions *may* not be the best decision. Personally, I would not want to drastically increase emissions in Pasadena, where I live, in order to reduce emissions elsewhere. Call me selfish, but I’m not a big fan of breathing yucky air.

    Really, I think we should look at “emissions” with goals for reducing maximum local concentration and total regional emissions. If design decisions result in increasing local emissions above a certain amount, then we may need to break down and open up new land for development, create new infrastructure, etc.

    Mike – I agree with you completely with the infrastructure argument. Infrastructure could be a *term* in our optimization problem. Here, you may get a positive measure for reducing infrastructure requirements, but that may come at a negative price to local emissions, or even overall emissions. So there is a trade-off, and we need metrics that will allow us to measure what’s a good balance.

  • Auto “Freedom” Is Bondage

    True Freedom, having multiple modes can prevent a localized increase of emissions. For example, New York City has very high density, but because a large portion of the population walks, bikes, or takes transit, localized air quality is superior to many other cities with lower density. If a community only has the “freedom” of the automobile, it is really in bondage to just one form of transportation.

  • Try TrafficLogistics, which gives both freedom and low emission. Look for future solutions, be bold, don’t think as people did yesterday. See http://trafikklogistikk.com
    regards
    Knut

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