We know D.C. Get our free newsletter to stay in the know.

Yesterday, TBD bemoaned the fact that parking downtown will get more expensive under D.C.’s new performance parking regime, illustrating the high occupancy rate of on-street spaces with samples taken by the Downtown D.C. Business Improvement District. The thing is, those samples by no means represent the totality of parking available downtown, because they don’t take into account a huge chunk of the supply: Parking garages.

Most office buildings have a large number of spaces set aside for their office tenants, and some have even more available for retail and general public use. According to the BID, the Washington Parking Association counted 45,721 spaces downtown and in the Golden Triangle in 2006—-compared to an estimated 17,000 public metered spaces across the city—-and the numbers can only have increased since then. Here’s the problem: Parking management companies are very secretive about how much parking they’ve got—-as Colonial told me when I asked about a garage in Georgetown, it’s “strategy.” The Downtown BID has so far been unable to collect enough information on private parking garages to put together any sort of market pricing system, and unlike San Francisco, D.C. doesn’t have many of its own.

So what’s to prevent performance parking on city-owned spaces from turning into a windfall for garage owners? Higher prices for curbside spots may cause drivers to keep their cars at home, or it may just send them into the nearest private parking lot. Unless the city’s willing and able to mandate disclosure of parking capacity, which would lead to a far more efficient system—-imagine an iPhone app that told you how many spaces were available where, and what they cost—-then its attempt to create a parking market will just get at a small part of the problem.

UPDATE, May 9 – Commenter TM points out, rightly, that it’s not a bad thing to force cars into parking garages—-much better than having them circle endlessly around downtown blocks. And though I’d be very happy about performance parking if I were a private garage owner, the city also takes a cut of that revenue with an 18 percent parking tax. Overall, though, it’s silly to say there’s no parking downtown. There’s plenty, and a perfect system would take it into account.