The city of Boston said Wednesday that it will extend a test of higher parking meter rates that resulted in more available metered spaces and less illegal parking in the Back Bay and parts of the Seaport district.

The city expects to decide by summer whether to make the pilot program rates permanent in the two neighborhoods, according to Transportation Commissioner Gina Fiandaca. It could also test the system in other areas with metered parking. Any changes to parking rates require the blessing of Mayor Martin J. Walsh.

“The results were successful in both the Back Bay and the Seaport District,’’ Fiandaca said. “Our goal is to create streets that work for everyone whether you walk, you bike, you take public transportation, or you drive.’’

In the Back Bay, where the hourly fee went from $1.25 to $3.75, there was an 11 percent increase in available metered spaces, and a 14 percent decrease in double parking, the city said. Instances of motorists parking illegally in spots reserved for residents declined by 12 percent, the city said.

City Councilor Josh Zakim, whose district includes Back Bay, said there’s anecdotal evidence that the pilot freed up parking in areas frequented by shoppers. But on the streets between Commonwealth Avenue and the Charles River, the price hike may have kept motorists away, he said.

“It certainly was an inconvenience to residents as well as visitors,’’ said Zakim.

In the Seaport, the city priced each block independently — between $1 and $4 hourly — and changed rates every two months based on the number of available spaces, officials said.

Weymouth resident Mike Clark, who visited the Seaport on Wednesday afternoon with his wife and two granddaughters, said the varying parking prices are confusing and unfair.

“It’s nothing but a tax,’’ said Clark, who paid $4.50 to park for 90 minutes on Seaport Boulevard. “The people haven’t had a say in it.’’

During the pilot, the number of available metered spaces rose by 1 percent in the Seaport, the city said. Cases of cars parked illegally in spots set aside for residents dropped by 35 percent.

The experiment’s impact on illegal parking was measured, the city said, by comparing parking tickets and other violations issued during the pilot to those handed out during previous years.

During the pilot, parking meter revenues increased by $5.7 million from 2016 in the Back Bay and $350,000 in the Seaport, the city said. The money will pay for street, sidewalk, and transportation infrastructure projects.

Martyn Roetter, chairman of the Neighborhood Association of the Back Bay, said the experiment has produced mixed reviews. Some people have complained that the $3.75 hourly rate is too high, and others are concerned about the neighborhood being singled out for a rate hike, he said.

He urged city officials to consider how other factors are affecting parking in the Back Bay, like utility companies digging up roads and the redesign of Beacon Street, which began in December.

“I think a return to the status quo is unlikely, but I would hope that there are some modifications and additions to the pilot program,’’ Roetter said.

Travis Andersen can be reached at tandersen@globe.com. Follow him on Twitter @TAGlobe. Laura Crimaldi can be reached at laura.crimaldi@globe.com.