How much parking is too much parking in Greater Boston?

Suzanne Kreiter/Globe Staff/Globe staff

Do we have too much parking?

The very idea might make Boston and Cambridge residents scoff. But the Metropolitan Area Planning Council has compiled some numbers that suggest some Greater Boston communities have a good bit more parking than they need.

Eric Bourassa, director of MAPC’s transportation division, says such data can help cities find what he calls the “Goldilocks” principle of parking: not too many spaces, not too few, but just the right amount.

This matters because the unused spaces could be used for badly needed housing, open space, or other developments. As more car-sharing options — from Uber to ZipCar — proliferate, the number of area residents who don’t need a car could increase.

MAPC, a regional planning agency, collected data on whether residents in Arlington, Chelsea, Everett, Malden, and Melrose were using all the parking that’s available to them. Researchers found that about 25 percent of parking spaces for multifamily residential buildings went unused between midnight and 4 a.m.

The group conducted surveys at 80 buildings with nine or more units to determine how much parking residents used. Researchers visited in the middle of the night to count how many cars were in each lot.

In all, almost 1,200 parking spaces were not being used, researchers observed. For every 10 housing units in the buildings they surveyed, an average of three parking spaces sat empty.

The findings confirmed the agency’s theory that developers were forced to build too much parking because of arbitrary rules written years ago, Bourassa said.

“These parking ratios are usually completely made up,” he said. “It’s often based on tradition, or what was established in zoning years ago and has never been touched.”

The researchers said there are several ways to deal with an oversupply of parking: reduce or eliminate minimum parking requirements, adopt parking limits, or mandate more shared parking.

This spring, the group hopes to expand the survey to include Boston, Cambridge, and Somerville.

As Boston booms with development, Bourassa said that giving city officials data on parking use could help them craft better policies on growth.

“Clearly, the city is grappling with this issue,” Bourassa said.

Transit Police: ICE isn’t on the MBTA

With President Trump’s administration promising a crackdown on immigrants who are in the country illegally, rumors have been flying about an increased presence by Immigration and Customs Enforcement officers in Massachusetts.

The rumors have even come to the Massachusetts Bay Transportation Authority. When police officers were seen conducting a security check at State Street Station this past week, some observers believed the searches were related to immigration enforcement. Photos of the checkpoint made their way to Twitter, where at least one person described it as an “ID check.”

But Richard Sullivan, superintendent of the MBTA Transit Police, says officers were merely checking bags, not asking for identification.

“We would not ever set up checkpoints on the MBTA system to verify anyone’s citizenship status,” he said. “It is not happening.”

The MBTA has been conducting random bag checks since 2006, Sullivan said. Officers run a swab over the bag, then place the swab through equipment designed to track explosives.

After receiving questions about the checkpoint, Transit Police felt the need to post a message on Twitter on Thursday night.

“Transit Police officers do NOT enforce Federal Immigration laws. We are here to serve EVERYONE,” the post read. “Security Inspection Program has nothing to do w/immigration laws/enforcement. Counterterrorism layer only.”