With three official working days left on their legislative calendars, the Massachusetts House and Senate may soon vote forward amendments that would allow Boston or other municipalities to lower speed limits in thickly settled or business districts.

After the Boston City Council voted unanimously in April on a proposal by City Councillor Frank Baker to lower speed limits in thickly settled or business districts to 20 miles per hour, state Rep. Dan Hunt filed a home rule petition on the matter with the Legislature’s Joint Committee on Transportation.

Amendments took shape in both legislative chambers as the proposal left the joint transportation committee. As the language stood going into a joint conference committee, which reconciles differences between the House and Senate bills, a municipality’s local legislative body would be allowed to “establish a speed limit of 25 miles per hour on a roadway inside a thickly settled or business district in the city or town which is not a state highway.”

Special “safety zones” could be designated by the same local bodies – including city councils, boards of selectmen, traffic commissioners – which would establish speed limits at 20 miles per hour. The safety zones could include school crossings, libraries, parks, elder centers, or other areas heavily trafficked by vulnerable populations, Hunt said.

Baker said he is “thrilled with how it worked out.” Although they asked for 20 miles per hour across the board initially, the safety zones offer some flexibility. “We’ll have that latitude to be able to scale that speed,” he said.

As the conference committee reviewed the broader municipal bill, both Hunt and state Sen. Linda Dorcena Forry remained confident the amendments would pass. “It’s about safety,” said Forry, who supported the adoption of the Senate amendment, “and how do we make sure that our residents in high-density population communities are safe.”

That municipalities are given the option of not adopting the speed limits offers flexibility towns and cities of varying sizes and needs, she said. “This may not work for every place, and we didn’t want to box people in.”

From a pragmatic angle, said Hunt, “the state didn’t want Boston to be 30, then you go into Quincy and it’s 20, and go into Braintree and it’s 15, all on the same road,” Hunt said. “Riders and drivers should have a reasonable expectation.”

Some legislators raised traffic concerns during the initial transportation committee hearing, which bill proponents said must be weighed with care against the safety improvements granted by moderate reductions in speed and heavier enforcement along those stretches.

“Just reducing it by five miles per hour will save lives,” Hunt said. Baker later concurred, adding, “I think in the city the differences are so small. If it adds one minute or two minutes to those commutes, I think it’s worth it.”