When construction on the Massachusetts Department of Transportation’s (MassDOT)  $255 million rehabilitation of the Longfellow Bridge gets underway in July, impacts will include extensive traffic diversions and interruptions to MBTA Red Line service.

At a public meeting last week, representatives from White-Skanska-Consigli – the joint venture firm awarded the design/build contract for the project – said northbound traffic on the bridge traveling from Boston to Cambridge will be eliminated and detoured to alternate routes during construction, which is slated for substantial completion on Sept. 30, 2016. The bridge will accommodate one traffic lane from Cambridge to Boston, as well as bicyclists and emergency vehicles. MBTA Red Line service across the bridge will be suspended for 25 weekends between this summer and the completion of track reconstruction in October of 2015, at which times inbound and outbound shuttles-buses replace trains.

Brimmer Street resident Alice Richmond was among those in attendance who objected to the proposed three-year suspension of outbound traffic on the bridge.

“For those of us living on Beacon Hill, it’s incomprehensible,” Richmond said. “I can’t imagine what’s going to happen on Cambridge Street if people can’t go north, especially with the hospitals [in the area].”

Bill Shea, a project executive, responded, “We hope our outreach program will get people to avoid the area.”

Thomas Tinlin, commissioner of the Boston Transportation Department, suggested testing the alternate travel routes to better gauge the project’s traffic impacts prior to the commencement of construction.

“What happens when the Bruins or Celtics are in town, or on the Fourth of July?” Tinlin said. “A lot of Rubik’s Cube pieces need to fall into place…and traffic diversion is the key to [the project’s] success.”

The next public meeting on the matter is scheduled for early summer, and MassDOT will establish a dedicated hotline and e-mail for the project before construction begins, according to White-Skanska-Consigli representatives.

The project’s scope includes a reduction in outbound vehicular traffic lanes from two to one to better accommodate bicyclists and pedestrians, the replacement of a pedestrian crossing between Charles Circle and the Charles River Esplanade, and improvements to MBTA Red Line tracks, among other modifications to bring the nearly 107-year-old structure up to modern code.