Metro stations attract economic development like flowers attract bees — or so we are told by proponents of transit-oriented development. With this argument, skeptical supervisors in Loudoun County are being urged to commit their constituents to an estimated $713 million in debt over the next 30 years by signing on to Phase 2 of Dulles Rail. The payoff comes when development around the two new Metro stations makes it all worthwhile.

But is this trade worth it? Where is the promised surge of development in Tysons Corner, where four Metro stations are currently under construction? With Phase 1 of the Silver Line scheduled to open next summer, nearly 15 percent of available commercial space there is unoccupied. The vacancy rate in Reston, where another Metro station is going up, is more than 17 percent.