Modern roundabouts boost traffic safety and efficiency | Civil Engineering Source

In the 1985 comedy film National Lampoon’s European Vacation, the character played by actor Chevy Chase drives his car into a circular intersection in London and then gets stuck there for the rest of the day, driving around and around the circle’s raised central island because he cannot figure out how to navigate the lanes and exit. Although exaggerated for humorous effect, the movie’s scenario is familiar to some traffic engineers. They understand that a driver who is not experienced with circular intersections can indeed be confused by a poorly designed system and can essentially feel trapped when confronted by other vehicles in the circle. The results can range from travel delays and backed-up traffic to collisions, injuries, and even fatalities.

Seriously, having been a transportation engineer for most of my life I am not a fan of roundabouts. While the picture in this article looks impressive a DOT very seldom has the room to design and construct a perfect one as shown here. I was also taught that roundabouts work best for lower ADT (average daily traffic) roads, a lower percentage of daily truck traffic, and that traffic volume should be relatively equal between the roads entering the roundabout or we will get some dangerous weaving patterns starting to take place along with an increase in speed. Well like them or not they are here to stay for at least the next 50 years or so; FHWA has been pushing the concept for the last 20 years or so. They didn’t catch on quick because us older engineers laughed and resisted designing them because we saw the damage caused by turning circles in our youth. As we retired, they are getting their way. Don’t get me wrong, in their place, with the correct criteria I mentioned being evaluated for the site, they can work quite well… in their place, not everywhere.