Over the last couple of years, Kasia Hart has spent a lot of time sitting in parking lots in the middle of the night.
Hart’s not a cop running a speed trap. She doesn’t drive a taxi or an ambulance. She’s a researcher at a local planning agency, trying to figure out whether cities and towns in Greater Boston are requiring new apartment buildings to have more parking spaces than they need.
The answer, Hart says, is usually yes.
She is lead author of a study being released Wednesday by the Metropolitan Area Planning Council, which surveyed nearly 200 apartment buildings inside Route 128 and found that about 30 percent of their parking spaces go unused, even in the wee hours of the morning, when most residents are likely home.
It’s a finding with major implications for the region’s housing crunch.
Building parking garages is expensive, and unused space devoted to cars can’t easily be repurposed for parks, plazas or larger housing units. Yet officials in many cities and towns, pressured by residents worried about losing on-street parking to newcomers, require new buildings to include a parking space for every unit, and sometimes more.
Such policies ought to be revisited, said Hart, who argues that more on-site parking encourages car ownership and is often not needed, especially in places well-served by the MBTA.
“These towns have a lot of opportunity to really shape development patterns in the future,” she said. “If you’re looking to build a community that has a lot of traffic and emissions and all that, build a lot of parking. If you want a community that’s more walkable and sustainable, build less.”
Hart led a team of MAPC researchers on the study, which simply counted how many cars were parked at 189 apartment and condo buildings in 14 cities and towns, between 11 p.m. and 4 a.m. In all, nearly 20,000 parking spaces were counted.
The researchers found empty spaces just about everywhere, with the average building’s parking lot about 30 percent vacant. Buildings with easy MBTA access to job centers, or with more affordable housing, tended to have more empty spaces. Buildings in higher-income neighborhoods, and — perhaps ironically — those that provided more parking per unit, tended to have fewer.
It’s an indication that parking requirements are often too high, said Tim Reardon, MAPC’s director of data services. The report estimates an average parking space costs $15,000 to build — far more in underground garages — a cost that’s then baked into rents, regardless of whether the space is used.
Reardon said there’s at least some evidence that the presence of on-site parking attracts higher-income tenants. That, in turn, causes everyone’s rent to rise.
“It creates an amenity that developers then charge for,” Reardon said. “Essentially, by creating lots of parking in transit-oriented areas, we’re driving up the cost of housing.”
There are places that are trying to go in the other direction.
The City of Boston, for instance, generally requires less parking at buildings in its denser neighborhoods, and close to MBTA stations. In recent years, it has permitted a few buildings with no parking at all — sometimes coupled with rules barring their future residents from even receiving on-street parking permits.
But the restrictions can face fierce pushback in places like Brighton and South Boston, where new development has surged and vying for a parking space on the street can feel like a blood sport.
Just this week, amid criticism from neighbors and local elected officials, the developers who want to turn the shuttered Edison power plant in South Boston into a 1.8 million-square-foot campus featuring housing and office space promised to incorporate more than 1,200 parking spaces into the project, including 120 set aside for neighborhood residents on nights and weekends — a deal specifically requested by US Representative Stephen Lynch, a Democrat.
Some inner-suburban towns are trying new approaches of their own. Arlington allows developers to build less parking than normally required if they subsidize T passes or pay a stipend to residents who don’t have cars. New buildings in Watertown can choose to rent out parking spaces, at market rates, separately from apartments. It’s an option that has proven popular with developers, said Laura Wiener, senior transportation planner in Watertown, and persuasive to neighbors worried about increased traffic on their street.
“The best argument for this is that it reduces traffic,” she said. “If there’s 10 cars for 10 units, instead of 20 cars for 10 units, there’s going to be fewer cars on the roads.”
The more flexible approaches to parking are an improvement over rigid space-per-unit rules, Hart said. And the region will need more communities to embrace such rules as the region grows more crowded, making every acre of asphalt that much more valuable.
“We counted 6,000 empty spaces in the middle of the night,” she said. “Imagine how many are vacant in the middle of the day.”
Tim Logan can be reached at email@example.com. Follow him on Twitter at @bytimlogan.