iStock photo

In an update to its landmark 2019 study, researchers at the Metropolitan Area Planning Council say excessive local parking requirements are continuing to drive up housing costs.

The latest iteration of MAPC’s “Perfect Fit” study examined 36 multifamily properties across Brookline, Concord, Needham, Newton, Sudbury, and Watertown in 2022.

Even at moments of highest demand, the study found, 4 in every 10 parking spaces in these developments were empty on average, a rate even higher than in earlier versions of the study. That pattern was observed despite a second trend the researchers said they found, that parking construction was the single largest factor in causing demand for parking to rise. That finding echoes previous versions of the study, which looked at new construction elsewhere in the Boston metro.

“In every municipality and at every development, parking was oversupplied,” Adi Nochur, senior transportation planner at MAPC, said in a statement. “Municipalities with the most parking per unit had the lowest utilization, meaning developers had to build hundreds of parking spaces that are not needed. This drives up housing and development costs, lowers housing production, and contributes to increased automobile usage and greenhouse gas emissions right when we are in the middle of housing and climate crises.”

The study found on average 1.58 parking spaces were offered per unit, while only 1 car per unit needed to be parked on average. Typically, parking construction is driven by municipal zoning requirements which sometimes stipulate as many as one parking spot per bedroom in an apartment or condominium development.

“Multifamily housing sites in suburban locations may have higher parking demand than sites in more transit-accessible locations, like MAPC’s Inner Core,” said Nochur. “However, the parking utilization research, now including this Phase 4 study, has consistently found that parking is oversupplied at sites throughout Greater Boston – whether urban or suburban.”

The latest research comes as towns and cities are debating how to implement their obligations under the MBTA Communities transit-oriented zoning law.

Newton officials, for example, cut parking requirements in some proposed zoning districts to make sure the development rules were more likely economically viable. Between the first and second iterations of the city’s proposed zoning reforms, vehicle parking minimums for both residential and commercial developments close to the city’s MBTA stations were removed, but bicycle parking requirements were retained.

Newton, Milton and other communities served by the MBTA’s subway lines must have new, transit-oriented zoning districts in place by the end of this year, while communities served by commuter rail trains and those near to MBTA rail service have until the end of 2024, while distant small towns have until the end of 2025.

“Watertown is excited to get hard data on utilization to inform public conversation about the amount of parking we require for multifamily housing,” Steven Magoon, assistant Watertown city manager, said in a statement provided by the MAPC. “This is perfect timing for such a conversation, as our draft comprehensive plan released three weeks ago recommends that we review the city’s parking requirements, and this helps us make sure that projects don’t have too much or too little parking.”