There is a thought process in land use planning that says moving jobs to the suburbs is a good idea, because a lot of people live in the suburbs and if they work there as well then they don’t have to drive as far to get to work. It’s a fairly intuitive idea, and one that many planners and community activists subscribe to.

Except it doesn’t work that way at all.

Not even close.

In actuality, people tend to live 15-45 minutes away from their job, regardless of where their job happens to be. The result is that people who work downtown tend to look for housing close to the core, while those who work far out in the suburbs look for housing far out in the suburbs. Of course there are some outliers. There will always be people who want to live in the city no matter what, or who commute in from Pennsylvania, but for the vast majority of people, this is how it works.

Take a look at these two maps, produced by MWCOG and initially published in the blogosphere at Greater Greater Washington:

Origin of commuting trips to downtown Washington (federal jobs only, but the private-sector map looks the same). The vast majority of commuters live inside the Beltway, and very few come from beyond Fairfax County.

Origin of commuting trips to Tysons Corner. Thousands come from Reston, Herndon and points west.

Think those downtown workers are the ones clogging I-66 and I-95? Not likely. The situation could not be more clear: If you want to foster Smart Growth and multi-modalism, put your jobs in the city. If you want to foster sprawl and congestion, put them far away. End of story.

PS: GGW has more maps for other job centers. The map for commuters to Ornjington (yeah, I’m sticking with it) is somewhere in-between, while the map for Reston/Herndon trends even more to the far-away western suburbs than does the Tysons map.