City leaders in Des Moines, Iowa, are among leaders in several cities across the nation that are rethinking the future of parking downtown. “They’re saying, ‘Don’t build parking lots, don’t build garages, you aren’t going to need them,’” said Councilman Skip Moore, citing city planners at national conferences across the country. And Altamonte Springs, Fla., solves its “last mile” problem, connecting popular destinations with public transit, by subsidizing Uber rides. It’s cheaper than building more parking garages.

The costs are even higher in the Bay Area, where we could be housing people instead of housing cars. As urban planner Donald Shoup writes in his now-classic book, “The High Cost of Free Parking,” parking spaces in San Francisco cost more than $34,000 each to build (in 2011), and take up 330 square feet of space. That is about the space needed for an apartment micro-unit. In the housing-starved Bay Area, that trade-off should be made explicit.

Parking standards are also under review in the planning bible that determines what will be built by real-estate developers in our state, the California Environmental Quality Act. CEQA assumes a predictable increase in car use when buildings go up, but the debate rages on around how much parking is adequate.

Those assumptions need to be completely re-thought in state and local discussions.

Three significant pressures are aligning that should give pause to investors in automobile parking garages. Garages are typically financed on a 30-year payback, either by cities or private investors. But they could find themselves holding the un-payable backend of a 30-year note, when folks stop driving within the next 15 years.

The first pressure, already evident, is from Millennials, who are simply not interested in driving. In part, this is based in the embracing of social media connectivity that makes connectivity via car unnecessary or burdensome. With fewer driver’s licenses and auto purchases among young adults comes decreased need for that parking garage space.

The second pressure is the technological advancement toward autonomous vehicles. As these vehicles are converted into “robot taxis,” which can be hailed with a tap on a cell phone app, the need for ownership of personal cars will decline, taking with it the need for parking.

Automated mobility services could capture two-thirds of the entire U.S. mobility market by 2030. And given that currently private cars may need as many as four spaces, for the combined destinations involving home, work and shopping, the entire market for parking garages will take a drastic hit. The Smart Cities Council argues that current thinking by cities on the impact of autonomous cars does not take parking into account.

The third pressure has to do with what must happen, as the first pressure has to do with what people want, and the second with what is emerging. Every expert on climate change agrees that to avoid global meltdown we have to drastically reduce the use of fossil fuels. That is, we have to stop using gasoline-powered cars.

So, within the next 15 years, there will be more reliance on transport by foot, bicycle and public transit. There will be more on-demand autonomous electric vehicles, which will circulate among users and spend relatively little time parked. Consequently, the demand for public parking garages will plummet.

The least that cities and real estate developers should do if they feel they need to build parking garages would be to design structures that can be easily converted into commercial, residential or other uses.

But the better advice is: Don’t build them, because they won’t be needed. And adopt local regulations that require justifying new parking, especially in cities served by transit. Otherwise, we all will be stuck with the bill.

Edward Church is the executive director of the nonprofit Institute for Environmental Entrepreneurship in Berkeley. church@enviroinstitute.org A version of this commentary was published in GreenBiz.com. To comment, submit your letter to the editor at http://bit.ly/SFChronicleletters.