Walking in Portland this week, I was struck by how much vacant land there is under the I-405 freeway immediately adjacent to the Pearl District, one of the country’s poshest redevelopment areas. There’s at least ten blocks of land there where buildings of four to ten stories could be built, and almost every major large metropolitan area has large tracts of this “fly-over” country. Given the difficulty of shoe-horning low-income housing elsewhere in the city, why aren’t we thinking about these sites?

Two reasons. The first is we’ve become accustomed to freeways and don’t think about how much land they use. The second is bureaucracy: no one wants to take on state departments of transportation, which have turned passive-aggressiveness into a science. But if we want to create more centrally-located housing, we need to scrounge for sites the way kids looked for metal in WWII. Whether it’s under or alongside the freeways, there is much land there to be had.