Unused parking spots driving up cost of housing

A WIDESPREAD OVER-SUPPLY of parking in metro Boston residential developments is driving up the cost of housing and may encourage people to own cars who otherwise would not, according to a new study by the Metropolitan Area Planning Council.

Over the course of three years, the council determined that during the peak-demand period – overnight on weeknights in the fall, winter, and spring – only about 70 percent of parking supplied by residential developments was being used.

Looking at the available off-street parking facilities at 189 developments with a total of 19,600 units, the council counted nearly 6,000 empty spaces, totaling more than 41 acres of pavement. The construction cost of those unused spaces totals an estimated $94.5 million, representing about $5,000 per housing unit in the survey.

State policymakers have struggled to find solutions in recent years both to bring down the cost of housing and reduce the traffic congestion around Boston. Boston has some of the highest rents and home prices, and it has the worst traffic in the nation, according to the firm Inrix.

“Cities and towns shape the region’s future through their local land use regulations, and ought to implement parking requirements that align with actual use and demand,” said Marc Draisen, the executive director of the Metropolitan Area Planning Council, in a statement. “During this research, we witnessed oversupply of parking in every surveyed community. Reducing excess parking can encourage more housing units at a lower rent or sales price. Aligning parking supply and demand at buildings near transit can also promote transit use over driving, which in turn alleviates congestion.”

People who don’t own cars may wind up subsidizing the car-storage costs of those who do if they live in a building where parking is provided to residents for free but factored into the cost of housing. The study recommends that the cost of car parking be unbundled from the cost of housing.

The council assigned blame for the over-supply to blanket municipal regulations that don’t comport to the needs on the ground.

“Requirements are often uniform across an entire municipality, and are rarely informed by real-world data about parking demand in existing developments,” the study said. “Almost none of these regulations account for how the need for parking may vary with development type, location, cost, or transit service. And since minimizing competition for existing on-street spaces – which can be a valid concern – is often the principle purpose of parking regulations, municipalities are naturally inclined to over-prescribe parking as a precaution against spillover.”

Finding parking in an area where it is in short supply can be a frustrating exercise, and as the study notes, neighbors often resist efforts to reduce the amount of off-street parking at proposed developments.

Meanwhile, the council found some evidence to suggest that the supply – or over-supply – of parking in residential developments helps drive the demand. The study said the number of parking spaces per residential unit was “the single biggest predictor of demand, suggesting that the availability of parking is attracting car-owning households and influencing their behavior.”

Traffic congestion isn’t merely a frustrating fixture for many Bostonians’ commutes. It also has global ramifications. Gas-powered cars spew emissions that worsen global warming. While gains have been made in reducing greenhouse gas emissions from other sectors – such as the power sector – transportation emissions actually increased between 1990 and 2016.

Draisen said that by adjusting residential parking to more neatly fit the need, urban planners will have an easier time encouraging walkable neighborhoods.

“The more parking that is provided, the more likely it is that residents will use it,” Draisen said. “By reducing parking supply to align with demand and pursuing additional transportation demand management strategies to promote alternatives to driving, we can reduce the barrier that excess parking places on the development of transit-oriented, walkable, and diverse communities.”

The parking-to-unit ratios at the developments observed varied from about four units per parking space to two parking spaces for every residential unit. At one quarter of the developments, less than half of the available parking was being used.

This legislative session lawmakers could take another run at changing local zoning law to encourage more housing production. The study by the Metropolitan Area Planning Council blames the amount of unused residential parking spaces on “excessive parking requirements in the local zoning code.”

The study recommends that new housing in areas with accessible transit connections should have less than one parking space per residential unit, and suggests bike storage, car-sharing, transit subsidies, shuttles, and “human-oriented design” as helpful features for developments near transit. Subsidized housing tends to need fewer parking spaces than market-rate developments and subsidized housing developments generate fewer car trips, according to the study.

“The costs of excess parking are particularly concerning for affordable housing developments, where scarce public subsidies are being used to build parking that goes unused by residents,” the study said. “Estimated construction costs for the 1,100 empty parking spaces we counted at majority-affordable developments totaled nearly $17.6 million, a sum that could have subsidized many dozens of affordable housing units.”