Roundabouts are still fairly new for Americans. They have caused some confusion like these poor drivers in Kentucky. Although, to be fair, the roundabout seems to be missing signs or road markings. In this article, we will be talking about some of the benefits of roundabouts followed by a bit about mixing roundabouts and automated cars.

What Are the Benefits of Roundabouts?

As more and more roundabouts pop up around the nation, some drivers are left wondering: are there benefits to going around in circles? Turns out the answer is yes – many. Here are the two biggest: increased safety and reduced pollution.

The Insurance Institute for Highway Safety reports that roundabouts have a:

• 90 percent reduction in fatal crashes
• 76 percent reduction in injury crashes
• 30 to 40 percent reduction in pedestrian crashes
• 10 percent reduction in bicycle crashes

This is mainly thanks to the reduction in conflict points. A typical intersection with a stop sign will have 32 conflict points with other cars and 24 conflict points with pedestrians. Meaning, 32 or 24 points where they could cross paths with a car or a person.

A roundabout reduces the conflict points by 70 percent to eight conflict points with other cars and eight with pedestrians. The vehicles are all traveling the same way and at lower speeds. This helps to increase the safety of the intersection too.

When a vehicle enters a roundabout, they aren’t required to stop if the way is clear. If there are cars in the roundabout already, all the waiting car has to do is yield for the passing car. No complete stops are needed.

Stop and go traffic increases the amount of pollution cars produce. Any time a car is idling, even for a minute, the pollution increases.

Roundabouts and Automation

Many people think automation is the future – especially for our cars. But, until every vehicle is converted over to an autonomous one, there will be a time when human-operated cars will be mixed in with autonomous ones.

The challenge is merging these two on the roads for maximum safety for all. If all the cars where automated, they could easily communicate and predict what the other cars will do. Its not so easy with a mix of vehicle types.

Several researchers are studying how to optimize this situation. There have been studies on optimizing the trajectory of automated vehicles around roundabouts. But those studies always assumed a 100% automated traffic stream.

Since we know cars won’t be 100% automated for a while, researchers at North Carolina State University wanted to develop a methodology for controlling the trajectory around a roundabout with a mixed traffic stream.

The solution relies on “convexification, alternating direction method of multipliers, and cutting plane decomposition components to tackle the complexities of the problem.”

Their methodology was found to reduce the travel time of the automated cars between 2.8% and 35.8%, increase the average speed by 4.7% to 96.3%and reduce the average delay by 9.4% and 98%. The researchers also found that their methodology increased the safety for the cars in the roundabout.