Rotary or roundabout . . . which is it?

Is there a difference between a rotary and a roundabout? Transportation experts at the University of Massachusetts Amherst have the answer.

In the first video of the University of Massachusetts Transportation Center’s series, “Transportation Take-Away,” center director Michael Knodler compares and contrasts the two circular traffic patterns.

Roundabouts are the more modern version of a rotary, Knodler explained in the video. They’re smaller, slower, and safer, he said. Massachusetts has even been phasing out rotaries in favor of roundabouts, the Globe reported last year.

The easiest way to tell one from the other is its size. Modern roundabouts are much smaller than rotaries.

While rotaries can have speed limits as high as 40 miles per hour, roundabouts permit speeds of just 15 miles per hour.

Roundabouts also have fewer “conflict points” for potential collisions, Knodler said. A typical traffic signal intersection has 32 such points; a roundabout has only eight.

Read the entire story at BostonGlobe.com