Somerville’s getting a brand new bike path with the Green Line extension. Is it wide enough?

The Green Line extenion under construction will have a bike path alongside.Lane Turner/Globe Staff/Globe Staff

Is 10 feet enough space for hundreds of cyclists to squeeze through Somerville?

Cycling and pedestrian activists in the city are worried that the long-awaited community bike path being built alongside the Green Line extension will not be wide enough to handle what they expect to be significant traffic once it opens alongside the expanded trolley service.

The path already extends past Davis Square, where it connects with the popular Minuteman Bikeway north of Boston, to about halfway through Somerville. For most of the route, the path is at least 12 feet wide.

The rest of the path will be built as part of the Green Line extension, which is scheduled to be completed in late 2021. It will run alongside the tracks all the way to Lechmere station and its nearby path network, creating a huge east-west throughway for cyclists north of Boston — but according to the MBTA’s latest designs, it is expected to be just 10 feet wide.

The Friends of the Somerville Community Path, an advocacy group that has long pushed for its completion, said that will not be enough space for a heavy volume of cyclists connecting between various path networks.

The group has cited federal guidelines that recommend bike paths be wider than 10 feet if they are anticipating more than 300 users during peak hours, or a high volume of pedestrians; paths should be at least 11 feet to allow cyclists to safely pass other users going in the same direction, the guidelines say.

The Friends expect far more riders than that to use the path. And Lynn Weissman, the group’s co-president, said that officials should hew toward the federal recommendations because the project is largely funded by federal grants.

The push for additional space comes as the project manager overseeing the Green Line extension, John Dalton, has cited “scope creep” as one of the major threats facing the project — that officials will be tempted to add new amenities.

The fate of the Somerville bike path has swung dramatically in recent years, and at one point was nearly wiped out. In 2016, when the MBTA rebooted the Green Line extension to address ballooning cost overruns, officials originally planned to cut a major portion of the path, sending cyclists onto the streets for the final leg.

But contractors who took over design and construction in 2017 said they could afford to complete the bike path in some form under the T’s newly tightened budget. In a statement, MBTA spokesman Michael Verseckes cited that tight money as one reason the T must keep the path 10 feet.

“In most areas, a wider path would mean constructing taller [and] stronger retaining walls and thus lead to greater costs,” Verseckes said. “Other portions of the path are carried on an elevated viaduct structure where a wider path would lead directly to a more robust structural design for the viaduct, columns, steel structures, and subsurface foundation elements — all of which would also lead to a more expensive path design.”

He added that in some areas of the planned path, the area is too narrow to widen it.

Karl Alexander, a volunteer with the Friends group, said it may make sense to pinch the path’s width in those select areas. But the T shouldn’t skimp on the broader design, he said, because a narrow route could create dangerous conditions for users. Spacing concerns have grown more acute since a 71-year-old man died in a head-on collision with another cyclist on the 12-foot Minuteman path in March, he added.

“We know there are very tight timeline and budgetary restrictions on this project. We understand that,” Alexander said. But, “it’s a safety issue and accessibility issue. We’re calling for an effort to adhere to design standards and best practices.”