Flickr/satguru

Researchers find a short-term approach and a long-term approach.

To cut down on some of the negative impacts of driving – greenhouse gas production, localized air pollution, congestion – people would need to drive a lot less. Bringing the average number of vehicle miles traveled, or VMT, per person down is widely seen as a practical step toward the goal of reducing the negative environmental and economic impacts of automobiles. New research suggests that average VMT could be cut by up to 20 percent with one of two relatively simple options.

The first option is to raise the price of gas. In a paper recently published in the B.E. Journal of Economic Analysis and Policy, researchers out of San Francisco State University find that raising the cost of driving one mile by 10 percent can result in an 18 percent decrease in annual VMT per household. That's like taking the bus to work every Wednesday instead of driving.

The second option is to increase a city's smart growth features by 10 percent. By increasing housing density, improving access to jobs and building more public transportation infrastructure, a city's average VMT per household could drop as much as 20 percent.

The difference between these two options is, of course, the time frame of implementation. Raising the price of gas can happen overnight, while building smart growth elements into communities can take years or decades.

But the time frames of their potential impacts are also very different. After a few weeks of gas being 10 percent more expensive than it used to be – $3.30 instead of $3.00 – the new higher price becomes the new reality and isn't really perceived as having as much sticker shock as it may have been at first. And because gas prices have been fluid for as long as gas has been sold, this sort of uptick in price is less likely to create much of a long-term change in any one driver.

The smart growth measures, on the other hand, are far more permanent than gas price hikes. The sort of community design, infrastructure and neighborhood layouts suggested by smart growth advocates would have a much longer lifespan and therefore have a much longer-term impact on driving habits.

So while both measures can reduce VMT by about one-fifth, only one can really do it effectively.

Top image courtesy Flickr user satguru

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