Hybrid Cars + Smart Growth = Carbon Knockdown

A car built in 2009 belches out 90 percent less tailpipe pollution as one built in the 1960s, according to Georgia Tech's Brian Stone. But the net benefits to the atmosphere have not materialized, because the average "vehicle miles" driven per person has tripled. So transforming what cars burn and how they burn it isn't enough: To amplify the impact that more efficient, cleaner cars may have on curbing air pollution and human-propelled carbon dioxide emissions, we also need to get smarter about how we plan our cities and other communities.

Creating more densely-populated cities and towns, providing them with good public transportation, and designing them to be bicycle- and pedestrian-friendly, would lower the number of vehicle miles we travel, and magnify the positive impacts of greener cars.

Stone is co-author of a new study that looks at the long-term benefits of combining smart-growth measures and hybrid electric cars. Considering several metropolitan areas across six states in the midwestern U.S., Stone and his colleagues projected auto vehicle emissions levels for a hybrid electric fleet between 2000 and 2050, and then looked at three scenarios of development:

• Business as usual (using census tract data on population, socioeconomic, and land-use changes from 1970 to 2000);
• A smart-growth scenario along the lines of the existing plan being used in Portland, Oregon;
• A hypothetical, more aggressive smart-growth scenario with an even larger population concentrated into urban and suburban areas.

Stone and his team found that if the only change between 2000 and 2050 was conversion to an all-hybrid  fleet, average emissions of CO₂ could be scaled back to 2000 levels.

Emissions could drop another 4 percent if we combine the all-hybrid fleet with the first smart-growth scenario.  Combined with the second smart-growth scenario of denser urban and suburban populations, emissions could drop another 6 percent -- adding up to 25 percent fewer emissions by 2050 than under the "business as usual" scenario.

“We show that it’s critical to have both technology and land-use policies to deal with CO₂because we won’t be able to reach Kyoto [Protocol]-like targets without [both],” Stone told Environmental Science and Technology News.  (Under Kyoto, industrialized countries are supposed to have reduced their greenhouse gas emissions to 1990 levels by 2000, and lower them about 5 percent more by 2012.)

The study is not trying to tell the future, but it offers some guideposts for policy makers and community planners to follow towards effective action on curbing global warming. “We’re not predicting this is going to happen" Stone said." But if it did happen, then how much would vehicle travel and CO₂ [emissions] change?”

In a way, this loops back to the Smart Growth Manifesto by Umar Haque that I posted a couple days ago, which looks at economic systems and behaviors, and argues for prioritizing outcomes over income, connections over transactions.  Stone's study considers community planning and design, but it's also assessing possible outcomes, and how taking a collective, multi-dimensional approach could create a positive, transformative outcome for the atmosphere -- which is to say, for us.

Image: New Columbia, a redevelopment in the Portsmouth neighborhood of Portland, Ore. Winner of the EPA's 2007 National Award for Overall Excellence in Smart Growth