In last week's Globe, reporter Kimberly Blanton and I wrote about the potential for gas prices to spur more Americans to abandon long suburban commutes, by choosing homes closer to Boston and other big cities or seeking towns with access to public transit.
The magnitude of these changes is debatable, and will depend a lot on how high gas prices get and how long they stay that way.
But as painfully high as gas prices are, and as frustrating as it can be to let them dictate how we live, many environmentalists and other antisprawl types are cheering. The cost of gas could diminish the appeal of distant suburbs in ways that gridlock and the aesthetics of big box stores have so far failed to do.
Urban planners blame the expansion of suburbs for a host of societal woes, and many trace their growth to the availability of cheap gas. Is this a rare moment to alter one of the most powerful trends in American history?
"There's a huge opportunity, I think, to develop in a different pattern that makes us less dependent on long automatic trips for all our daily needs," said Joe Cartright, an economist who just published a paper called Driven to the Brink, on behalf of CEOs for Cities, a research organization supported by government and business.
Housing patterns, and how far Americans drive as a result, play a big role in global warming. It sounds basic, but the issue has gotten far less attention than debates over the gas mileage our cars get and the need to develop cleaner alternative fuels.
To reduce enough greenhouse emissions in the next 40 years to tackle global warming, Americans need to focus on all three issues - fuel economy, alternative energy, and miles driven, said Deron Lovaas, a transportation specialist with the Natural Resources Defense Council.
Lovaas is hopeful that the trillions of miles Americans drive every year are finally getting some notice.
"I think it's coming to the public consciousness," Lovaas said. "Four dollars a gallon makes me conscious of that."
Since the postwar suburban boom and the rise of interstate highways, Americans have driven increasingly farther. In 1970, the average driver logged 9,949 miles per year, according to the Federal Highway Administration. That surged to 14,862 by 2006, the last year the statistics are available.
Massachusetts, a compact state with a large transit network, has a much lower average: 11,702 miles per driver in 2006.
The far-out suburbs have given many more Americans the opportunity to own a comfortable home. People who live in older, denser cities with better public transit leave a smaller carbon footprint, according to a recent study by the Brookings Institution. The study ranked the Boston area's carbon footprint per person the 20th smallest, out of 100.
The last few months have seen record declines in the combined number of miles driven by Americans, most likely the result of fewer trips to the grocery store, shorter vacations, and other lifestyle changes.
Are we really on a long-term path toward fewer miles? A decline in driving during the late 1970s gas crisis did not last.
"People are still moving around," said Doug Hecox, spokesman for the Federal Highway Administration. "They still have to go to the bar on Friday. They still have to pick up the kids from school."
(Hopefully, not in that order.)
But the point is well taken. More permanent changes in lifestyle will probably require more permanently high gas prices. And even then, not all economists believe they will hold much sway in where people decide to live.
"I'm a big supporter of cities and I would love to see this happen," said Ed Glaeser, a Harvard economist. But "it's hard to imagine that this is going to have a huge push into the city."
Glaeser contends that only commuters who drive 50 miles or more to and from work could see a significant savings in gas compared with other factors that influence the housing market. School systems and tax systems are set up to favor the suburbs over the city, he said. Americans are far more likely to trade in gas-guzzling vehicles than homes, he said.
Still, gas prices are beginning to climb into uncharted territory, and there may be surprising effects.
The price of gas was never a factor in buying a home in the past. Now, counselors who help first-time home buyers are telling their clients to consider fuel costs when they add up the price of a new home, said Marc Draisen, who leads the Boston Metropolitan Area Planning Council.
"A lot of people are suffering with high gas prices, and I don't mean to make light of that," he said. "On the other hand, the pattern of increasing land consumption and increasingly long commutes to work is not sustainable in the long run."
The ramp at I-90 east Exit 24B and Exit C to I-93 north and south will close 11:30 p.m. to 5 a.m. today and Wednesday.
Noah Bierman can be reached at firstname.lastname@example.org.