Via Walking in Seattle: A nifty new tool called Abogo, from the Center for Neighborhood Technology, shows you how much people in your area spend on transportation costs in a typical month. As we've written previously, the typical definition of "affordable" housing---which tends to be in far-flung suburbs that require long drives along sprawling freeways to get to work---includes only the cost of a rent or mortgage and ignores the cost of transportation---which, in the suburbs, can amount to more than half of household income.

Abogo gives a graphic demonstration of where people pay more and less for transportation. Here, for example, is the central part of North Seattle. Dark-green areas are neighborhoods where average household transportation costs are less than $730 (in this case, I searched for the 98102 ZIP code, where the average monthly cost is $694)

Here, for comparison, is Black Diamond, a former farming community-turned bedroom community for people who commute to Seattle and elsewhere (red areas are those where monthly transportation costs exceed $930; in Black Diamond's case, the average is $1142):

In other words, you'll save nearly $500 a month if you live in, say, the University District instead of a suburb like Black Diamond! (Maple Valley, a slightly closer-in suburb, clocks in at a monthly average of $1,040).

Incidentally, I also checked out some other cities to see how they compare. In San Francisco, the monthly average is $576. Washington, D.C., the monthly average is $557. In Los Angeles, it's $472. In Brooklyn, it's $436.

So the next time you hear someone justify moving to the suburbs because "it's cheaper," you might remind them that driving everywhere isn't free---and gas prices aren't getting any lower.