By Jeff Kuhn, PE, VP - Civil Engineer November 17, 2021
The new roundabout intersection of Douglas County Highways 8 and 40 provides drivers improved safety and efficiency at a lower initial and ongoing cost to the county.
Three things you probably don’t want to bring up in mixed company: politics, religion, and roundabouts. Even by another name—traffic circles, rotaries—reactions range from love ‘em to hate ‘em, with seemingly few points between. In actuality, they’re probably just misunderstood.
Roundabouts have grown in popularity among transportation agencies and road designers for their improved safety and traffic flow. And since vehicles can pass more quickly and efficiently through a roundabout, there is less queuing and idling, resulting in fewer emissions and better fuel consumption.
According to the Minnesota Department of Transportation (MnDOT), roundabouts are credited with an 86% decrease in fatal crashes, an 83% decrease in major injury crashes, and a 42% decrease in overall injury crashes at intersections. The North Dakota Department of Transportation (NDDOT) indicates an 82% reduction in severe crashes when comparing roundabouts with two-way stop-controlled intersections, and a 78% reduction in severe crashes when comparing roundabouts to a signalized intersection.
Clearly, in specific applications, roundabouts are a safer alternative to the types of intersections most of us grew up with.
To illustrate, when Douglas County, Minnesota, wanted to improve the junction of County Highways 8 and 40, they took several issues into consideration: initial cost, ongoing maintenance, and safety.
The existing intersection was skewed—that is, the highways did not meet at right angles. This creates sightline issues for drivers; the vehicle’s frame, or door post, may block the driver’s view of approaching cross-traffic. The County’s Intersection Control Evaluation (ICE) Report compared replacing the junction with a squared-up, signalized intersection versus a roundabout. The roundabout solution offered increased safety at a lower cost. The County worked with Widseth (project engineer) and MSA Engineering Consultants (technical consultant) to ensure the intersection met design standards while retaining flexibility for future developments and possibilities.
Roundabouts are sometimes wrongly accused of being significantly more expensive to develop. True, they often require a good deal of reconstruction to get the approaches right—forming the circle; creating the curved approaches; correcting skewed roadways, adjacent hills, or other geometric issues—but the additional cost is minor compared to constructing a signalized intersection. Currently, signals are approximately $250,000 per leg (i.e., each roadway that radiates out from the intersection), and they tend to be more costly to maintain.
Those who express an aversion to navigating roundabouts also frequently vow to avoid them at all costs. As more roundabouts are implemented, however, avoiding them is becoming difficult. MnDOT and NDDOT offer ample educational materials, videos, and websites to help drivers learn how to use roundabouts. Here are a couple of resources to check out:
And with greater knowledge, perhaps, will come increased comfort—and, might we suggest, a little love for roundabouts?
Contact Jeff Kuhn, PE, to look at options to improve roadways in your community or under your agency’s jurisdiction.