CAMBRIDGE — The unusual design of a separated bike lane, recently installed in a busy section of Kendall Square, has thrown some cyclists for a loop.

The striped lane appears as cyclists merge from Main Street and turn toward Third Street before crossing Broadway. The track, which is raised above street level, has what cyclists call a “pinch point,’’ a section that abruptly narrows. In this case, the lane is obstructed by a portion of a concrete block that juts into the right-of-way.

“It’s a little bit weird that they would cut a bike lane in half for a cement barrier,’’ said Gene Dolgin, who bikes through the area regularly on his commute.

But city officials said engineers had their hands tied when it came to the design. The structure impeding the lane contains a venting system for an underground pump room that’s connected to a nearby fountain and art display, and it couldn’t feasibly be moved.

“It has a complex set of controls underground. There are round holes facing toward the bike lane, and that’s a vent that lets air in, which needs to get moved through to cool the pumps and the machinery down there,’’ said Joe Barr, director of the city’s traffic, parking, and transportation department. “It would be a much more massive undertaking to get rid of it.’’

Barr said construction is still going on in the area, which presents opportunities to make safety adjustments, such as adding a reflector to the structure or shaving it down a bit if necessary.

“It’s not a perfect situation, but we know it’s safe and we know it meets the standards,’’ he said. “We hope everyone will be flexible.’’

The narrowed lane was brought to the forefront this week by Steve Bercu, president of the Boston Cyclists Union, an advocacy group.

Bercu tweeted a picture of the bike lane and concrete block, its unexpected edge forcing the white-painted line to curve, using the hashtag ­#ShinguardsRecommended.

In an interview, Bercu said the design is symbolic of Cambridge’s attitude toward the needs of cyclists.

“What it says to people on bicycles is that it’s OK if we give you a very compromised piece of infrastructure,’’ he said. “It says, ‘We can have a bike lane that’s suddenly constricted by a stone slab, and paint some lines around it, it’ll be OK, you’ll figure it out.’ ’’

Bercu said the city would never treat infrastructure for cars the same way.

“It would just never be acceptable,’’ he said.

On Friday, cyclists had mixed reactions to the jagged corner.

“I really like that I have a separate lane for this part,’’ said Sytze Harkema, who has been biking through the area for four years. “It’s not a problem to me. Bicycles don’t ride two parallel here. I wasn’t surprised by it.’’

Harkema’s greater concern was the overall Main Street reconstruction project, specifically where the busy road connects to Third Street and Broadway.

Cyclists coming from Main Street have to ride up onto an island amid throngs of pedestrians flowing from the nearby Kendall Square T station, and then quickly shift over to the curvy stretch of path where the concrete block stands.

Many avoided the small lane altogether, opting to ride in the street against oncoming traffic.

“I was questioning how bicycles would get on this lane,’’ Harkema said.

Karola Klarl, a German exchange student who bikes everywhere, agreed with Harkema, and said the merge from Main Street, over the island, is confusing and difficult to maneuver.

“It’s strange,’’ she said.

As for the concrete block in the bike lane? There’s nothing like that in her home country, she said.

“It’s not perfect. It shouldn’t be there, no,’’ she said, letting out a slight laugh before zipping down Third Street.

Steve Annear can be reached at steve.annear@globe.com. Follow him on Twitter @steveannear.