The city has begun adding bike and bus lanes to Boylston Street, kicking off weeks of intermittent road work along with furious debate among residents and commuters.

Boylston’s redesign comes courtesy of the Back Bay Mobility Projects, a sweeping initiative covering almost the entire neighborhood. Workers broke ground for the Boylston section on June 9, with the aim of installing bus and bike lanes, changing parking with new moped loading zones and new signals separating turn lights from crossing periods.

The redesign will be starting on Massachusetts Avenue and working its way east to Arlington Street. Sidewalks will remain open, but planners do anticipate the need for parking restrictions around affected areas.

A city spokesperson said they expect work to continue for about three weeks, probably ending near the start of July. Workers will be installing new markings and flex posts at night, saving daytimes for signal changes and sign installation.

"The changes on Boylston Street will make the roadway safer for all who live, work and visit in the Back Bay, improving speed and reliability for the more than 13,000 people who ride on the bus each day,” said the Boston Transportation Department (BTD).

“We’ve worked with local residents and business owners to gather feedback, which will improve pedestrian safety, update curb regulations, and reduce conflicts between the thousands of pedestrians, drivers, bicyclists, and bus riders who travel Boylston on a typical weekday.”

A recent survey by the Neighborhood Association of the Back Bay indicated the second most concerning issue for residents were safety conflicts stemming from cars, pedestrians and cyclists sharing the road. The new separated lanes from Mass. Ave. to Arlington may help address that but do come with drawbacks.

The new layout’s bus infrastructure will squeeze Boylston down to a single standard lane from Ring Road to Copley Station from 4 to 7pm on weekdays, a decision that prompted frenzied objection from some residents online.

Even two-lane streets in the Back Bay are frequently at risk from double parkers due to lax traffic enforcement, but city planners are apparently unconcerned with that possibility. Spokespersons for the BTD stopped responding to questions when asked about whether the city had concerns, what studies they’d performed and whether a plan was in place to remove the changes if they prove unworkable.

The new layout will also cost roughly 100 parking spaces, dropping the street’s total from 324 to 236.

City Councilor Ed Flynn has been among the most outspoken critics of the changes.

A forum he held on June 5 saw a strong showing from cyclists in support of the project, but he said in a June 14 interview that his position hadn’t changed.

“My goal was to listen to the voices of residents, and the business community. It’s clear to me that the BTD officials did not listen to recommendations made by either. It’s true that there are a lot of people that use Boylston that do not live in the Back Bay, but I believe this plan implemented by the BTD without any real input from the business community will have a negative impact on businesses.”

Despite opposing the project, Flynn declined to say which specific elements he would like to see changed, or to specify what steps he would have liked to see from the BTD during outreach efforts.