Traffic Engineering Wizardry from 1972
The roundabout pictured above is referred to as the “Magic Roundabout.” It is located in Swindon, England (from Oxford, just drive southwest on the wrong side of the road for approximately 50 km).
This magic roundabout actually consists of seven roundabouts and has worked great since 1972 (nevermind it was voted the fourth-scariest junction in Britain in 2009). In a traditional roundabout, cars move in one direction. In the magic roundabout, cars move in both directions (please stop attempting this in Indiana).
Roundabouts have noteworthy advantages. From a safety perspective, roundabouts reduce traffic injury accidents by over 70% as compared to traditional intersections. And fatal accidents all but disappear. Granted, some roundabouts could be more intuitive — some roundabouts, well, let’s just say it, could use serious tweaking — added pavement markings, different signage, or maybe even a detour sign…
And as magical as they may be, roundabouts are not the answer for every intersection. For example, they need more land at the intersection itself. That’s offset somewhat since they do not require extra roadway width for turn lanes on the approaching roadways. Overall however, land requirements for roundabouts are less than that required for traditional intersections.
One of the most noteworthy features of a roundabout (aside from being magical) is they do not need to be warranted — they do not need a particular traffic volume to justify construction. A traffic signal on the other hand, does require specific traffic volumes — it must be warranted — whereas a roundabout can be constructed anywhere. If it makes sense, do it! Just be certain it also makes sense after you do it — that’s the magical part…
Chet Skwarcan (traffic engineer, author, unique insights) with over 25 years of traffic engineering experience — online ideas available at TrafficEngineering.com/Services.