Massachusetts took a big step in 2024 when the Legislature legalized so-called “accessory dwelling units” statewide as part of an effort to rein in the state’s housing crisis. More than a year later, it’s clear that the law is working — but that it also needs tweaks before accessory units can meet their full potential.

These small units, nicknamed “granny flats,” can be constructed in someone’s backyard, or they can simply be renovated third floors, garages, or basements. They’re a popular option for seniors seeking to downsize and families looking for some rental income.

Prior to the state law, some communities allowed accessory units, but many did not. Even among those cities and towns that did tolerate accessory dwelling units, zoning often varied from one municipality to the next, making it difficult for builders who needed to decode each municipality’s rules. Some towns also included unreasonable restrictions, like requiring that only a homeowner’s family members could live in the accessory units.

Housing advocates viewed allowing accessory dwelling units statewide as a “low-hanging fruit” policy — a way to add housing that was relatively cheap and avoided some of the cost and political obstacles that housing measures often encounter. The state legislation also overrode some zoning restrictions, including those that limited accessory units to family, while leaving some other local rules intact.

One year after the law went into effect, this approach has proved fruitful: Towns across the state have approved 1,200 ADU permits and seen even more applications, in some cases up to a threefold increase from previous years.

A study published last week by Boston Indicators (the research branch of the Boston Foundation) and Abundant Housing Massachusetts found that forcing the hand of municipalities on accessory dwelling units accomplished more in one year than 50 years of zoning reform efforts at the local level.

The problem, though, is that municipalities retained too much power. As the study recommends, there should be clear, uniform state regulatory standards for ADUs, with minimal opportunities for municipal-level variation.

“A comprehensive agenda is needed to address regulatory barriers to housing production, spanning building, fire, energy, septic system, wetlands, and stormwater rules,” the study’s authors wrote. “The barriers include the fragmented complexity of the regulatory system itself.”

Making standards more uniform doesn’t have to mean lowering them — it just means moving away from patchwork rules that make it harder for companies to build accessory units at scale.

Chris Lee at Backyard ADUs, a company that designs and builds modular dwelling units in New England, says the report’s findings make sense. The inconsistent interpretations across 350 towns and cities cause builders and engineers to “struggle to design work for the town that will be accepted,” he said. (The state’s 351st municipality, Boston, isn’t covered by the law.)

The potential is significant. The report calculates that if just 2 percent of single-family homes in Massachusetts added an accessory unit, the state would see more than 30,000 new homes that advocates say are generally more affordable. Building an accessory dwelling unit inside a pre-existing house can cost between $75,000 and $100,000; and a detached unit usually runs between $250,000 to $350,000, making them much more affordable than purchasing a single-family home in most regions of the country.

“For developers of missing middle housing to benefit from an economy of scale, they have to undertake many projects, across jurisdictional lines,” according to the study. “The ADU case study has shown just how challenging this is.”

Lee estimated that he could reduce up to $30,000 of preconstruction costs such as surveying and architecture if his company could work with consistent regulations across towns, which he said could enable them to double their production.

Streamlining permitting for accessory dwelling units isn’t a panacea. Landlords still must be willing to actually build them and rent them to long-term residents. Retirees must believe it’s worth downsizing to one. But the fact that so many have been permitted over the last year point to the clear demand and makes the case for policy makers to keep refining the law.

There is precedent. California, for example, had an equally ambitious goal but has blown past it, going from only 1,300 permits approved its first year to more than 30,000 nine years later. “It is important to understand that California did not accomplish its ADU outcomes with one legislative reform,” the study’s authors wrote. “California’s success required sustained legislative attention.”

Massachusetts should be able to realize those kinds of results too. Conversely, if even the “low-hanging fruit” of zoning reform falters in the Commonwealth because of local red tape, then the state has bigger problems ahead to solve its housing crisis.

Editorials represent the views of the Boston Globe Editorial Board. Follow us @GlobeOpinion.

Reports of an explosion from people across New England Saturday afternoon sent police agencies and others scrambling to understand what caused a double boom that shook buildings in Massachusetts and Rhode Island.

The American Meteor Society said that the booms heard about 2:30 p.m. were actually caused by a meteor about 3 feet (nearly 1 meter) wide entering the atmosphere around the New Hampshire border with Massachusetts, north of Boston.

Fire program monitor Robert Lunsford said the society received dozens of reports from Delaware to Montreal with people either hearing the double boom, feeling the ground shake or seeing the fireball — which he said looked like a shooting star in the daytime sky.

“It was definitely bigger than a normal fireball, about a yard wide,” he said.

But Lunsford said it’s unlikely the meteor struck the ground.

“We would need more information about the trajectory the speed and other aspects to know for sure if it hit the ground, but if it didn’t burn up, then it would have landed in the ocean,” he said. “Most of them do burn up before they hit the ground.”

People in a handful of states posted on social media about feeling the buildings they were in shaking. Several videos on the X platform captured what sounded like two quick booms, with no fire, smoke or other visual causes.

Several people filed reports with the U.S. Geological Survey, registering the shaking they felt with the National Earthquake Information Center, agency spokesman Steve Sobie confirmed.

The agency opened an event page, based on the number of “Did you feel it?” reports it received on its website. But Sobie said there was no event registered on the agency’s seismographs. meaning the shaking was not due to an earthquake.

A Greenfield, Massachusetts family of four were among the five killed when a bus plowed into vehicles on a Virginia highway early Friday morning. A 25-year-old woman from Worcester was also killed in the crash. 

It comes as investigators are trying to piece together what happened in the collision that injured dozens more. 

There is profound sorrow in the Greenfield community. Heartbroken family members say Dmitri Doncev, 45, his wife Ecterina, 44, their 13-year-old daughter Emily and 7-year-old son Mark all died after a charter bus slammed into their car and others on I-95. The Worcester woman who was killed was in another SUV struck by the bus. 

They Doncev family were devoted members of a Russian Baptist Church who were heading to a wedding in South Carolina. 

The heartbroken family sent WBZ a statement saying, “Today, words cannot adequately express the pain and sorrow felt by their family, friends, church community, coworkers, classmates, and all who had the privilege of knowing them. Their absence leaves a void that can never be filled, but their memories, their love, and the countless lives they touched will remain forever in our hearts.” 

“Though their time with us was far too short, the legacy of kindness, faith, perseverance, and love that they leave behind will continue to inspire all who knew them,” the statement said. 

Providence Christian Academy said the children attended the school saying in a statement, “The Doncev family was a cherished part of our school community, and their loss is being felt deeply by our students, families, faculty, and staff.”

Greenfield Mayor Greenfield Mayor Virginia DeSorgher also said in a statement: 

“To the families, friends, and neighbors of those we lost: there are no words that can fully ease the weight of this sudden and unimaginable grief. Please know that you are not walking through this dark time alone. The Greenfield community stands with you, mourning alongside you, and we extend our absolute deepest condolences and prayers.” 

Investigators say the bus did not slow down in a work zone, hitting several cars in front of it. Passengers on the bus woke up to chaos. 

“It was horrible,” said bus passenger Wayne Tobin. “It was just like blood everywhere; it was people holding their head. Their heads were bleeding.” 

In all, about 44 people were rushed to area hospitals. 

State police identified the bus driver as 48-year-old Jing Dong. He could be facing charges in the crash. 

Transportation Secretary Sean Duffy said on X that Dong was an American citizen originally from China who got his commercial driver’s license two years ago in New York.