These days, real estate is no longer primarily about your house, how much you value it and how much others value it. Why? Because transportation, its cost increasing as oil supplies tighten, demand for fuel grows and gas prices spike, looms ever larger in the real-estate equation.

Put simply: The shorter your commute, the more value your house has; conversely, the longer your commute, the less value your house has.

Sound crazy? Consider this recent report by National Public Radio. The upshot is that house prices are plummeting in metro areas that are sprawled out and where homeowners must drive farther to work or to accomplish daily tasks. Conversely, house prices are either rising some or decreasing far less in metro areas that are not as sprawled out and where homeowners enjoy shorter commutes.

Jonathan Hill, vice president of Metropolitan Regional Information Systems, which tracks home sales, told NPR that he found a lot of negative numbers in ZIP codes farther away from central cities but not in places that are close in or near public transit. On the contrary, in those places the average sales price was up.

David Stiff, chief economist for the company that produces the Case-Shiller Home Price Index, saw the trend in other cities, too, including Los Angeles, San Francisco, New York, San Diego, Miami and Boston. According to NPR, Stiff matched home resale values against commute times and found that in most of these major metro areas, the trend is the same: The longer the commute, the steeper the drop in prices.

Stiff said homebuyers' attitudes are changing. The old rule was, "Drive 'til you qualify," he said, meaning they should trek out from the city until they find a house they can afford. Now, buyers are asking, "What is the cost of gasoline? What is the cost of my time?"

I searched high and low to find any similar analyses of the Puget Sound region but came up empty. Nevertheless, it's reasonable to conclude that one reason why our region's real estate market isn't hurting as much from a battered economy is because our houses (condos and apartments, too), generally speaking, are located near public transportation and other important services, and mostly reside within urban growth boundaries that cut down on sprawl and, therefore, long commutes. According to the Puget Sound Regional Council, data show our use of transit is high and that our region's anti-sprawl growth policies are working.

Of course, it helps that our economy is doing well, mostly because we still make and grow things that people want, including airplanes, software and apples. But our land-use policies and a decent helping of alternatives to driving long distances help tremendously, too. I would hazard to guess it's one of the reasons PMI Group thinks the likelihood of lower house prices in our region in two years is unlikely. According to its report, that likelihood was 3.8 percent in the fourth quarter of 2007, down from 7.1 percent in the prior quarter.

So, we're OK, right? Not necessarily. Doug McDonald, former transportation secretary for Washington state, wrote an intriguing opinion piece for Crosscut that makes the case for retooling our growth policies and population projections to better govern land-use and transportation in our region.

Also, even though transit ridership is up and many of us live near essential services, our traffic congestion continues to grow and become a drag on our economy, our quality of life and our ability to get to and from our valuable houses. Toll roads would help in a big way, as this story by the Seattle Times points out, although there are some pretty big fairness issues to work through. Last year, I wrote about congestion pricing and the region's fractured management of land-use and transportation policies. Check it out here.

To be sure, the new real estate equation ? that the value of your house increasingly is tied to how much time you spend in traffic ? may be temporary. Markets change. So do attitudes. Oil prices fluctuate. But I doubt we're going back to $1.25-$2.25 for a gallon of gas. The market is perhaps as ready as it ever will be to support additional building in cities and in close-in neighborhoods. (Question is, will city schools improve and will some middle-class families, which cities need to be successful, stay in or move back into urban centers or close-in neighborhoods?)

In any case, livable cities where you own a house with added value and walk or ride a bike to accomplish tasks (or to just get some air), or where you take your car for a short spin, are no longer the dreamy wishes of urban planners. Not that there's anything wrong with dreaming.