Traffic is going in circles. Armed with mounting data showing that roundabouts are safer, cheaper to maintain and friendlier to the environment, transportation experts around the country are persuading communities to replace traditional intersections with them.

There’s just one problem: Americans don’t know how to navigate them.

“There’s a lot of what I call irrational opposition,” said Eugene R. Russell Sr., a civil engineering professor at Kansas State University and chairman of a national task force on roundabouts, sounding mildly exasperated in a telephone interview. “People don’t understand. They just don’t understand roundabouts.”

But many are being forced to learn, 25 years after Clark Griswold captured the public’s unease with roundabouts in “European Vacation,” spending a full day circumnavigating London’s famous Lambeth Bridge roundabout  “There’s Big Ben, kids! Parliament!”  unable to escape its inner lane.

The Department of Transportation does not keep statistics on roundabouts, but experts agree that they are proliferating rapidly. They point to Wisconsin, which has built about 100 roundabouts since 2004, and plans to build 52 more in the 2011 construction season alone. Maryland is closing in on 200. Kansas has nearly 100.