As I Bike TO readers plumb the minds of suburbanites to find out why they continue to buy houses in the suburbs, they may be interested in this study by the Brookings Institute which has created an index map of housing + transportation affordability and correlated it to an index of local median wages to show locations of affordability. As it turns out, living in the suburbs doesn't look quite as appealing when we take into account the transportation costs.
In this example map of Chicago you can see the "affordable" yellow areas where housing + transportation are within 0 to 45 % of median income and the blue are above. The results rub our assumptions the wrong way: living in the suburbs is often not that cheap. It just so happens that it's a lot easier to calculate our total housing costs than total transportation costs.
The site says:
"The Housing + Transportation Affordability Index, developed by CNT and its collaborative partners, the Center for Transit Oriented Development (CTOD), is an innovative tool that measures the true affordability of housing. Planners, lenders, and most consumers traditionally measure housing affordability as 30 percent or less of income. The Housing + Transportation Affordability Index, in contrast, takes into account not just the cost of housing, but also the intrinsic value of place, as quantified through transportation costs."