MASON CITY — Could roundabouts be in Mason City’s future?

The City Council in Mason City last night held a workshop session prior to their regular meeting to hear a preliminary report on potential reconstruction plans for State Highway 122 between Winnebago Way and the western city limits. WHKS was hired by the city to do a feasibility study on potential options for improving the highway, with three options presented during the workshop. One option is doing nothing, another is improving the traffic signals in that stretch, while the other looks at establishing roundabouts at the intersections where traffic signals currently are placed between Eisenhower Avenue and Winnebago Way. 

WKHS project manager Scott Sweet says the potential for accidents decreases with roundabouts compared to the current highway makeup. “You can see there’s 42 conflict points, basically a conflict point is where two vehicles cross paths. The more conflict points, the more decisions you have to make, and more accidents you have. With a roundabout, you’re down to 24 conflicts. Probably the important one I look at are the crossing maneuvers, where your broadside and probably some of your more severe accidents happen. You’re looking at 24 for a signalized intersection with only eight for a roundabout.”

Sweet says the average speed getting through that stretch of highway would be increased with roundabouts.  “The average speed if you are going from Eisenhower to Winnebago Way with the traffic signals if you just drive it, it would be like driving at 25 miles per hour. With the roundabout, you’d be in the 38 MPH range. It’s a lot more free-flow, you don’t have platooning of vehicles. Platooning is what you get when you stop at a stop light and all the cars back up, and then they all go at once, and then they go to the next stop light and you stop again.”

Sweet says when using the 25-year projected traffic counts, the average amount of time getting from the western city limits to Winnebago Way would be cut by more than half with establishing roundabouts.  “Basically the delay as you go all the way through to Winnebago Way is about 200 seconds on that trip. That’s for the ‘do nothing’ alternative. When you look at the traffic signal alternative, that delay is basically cut in half. You are down to 108 seconds, which is a little over a minute extra that you possibly on average are sitting there. As you look at the roundabout, it’s maybe three-quarters of what it is for the signalized, you are down to 78 seconds.”

The estimated cost of either of the reconstruction projects is $50 million, with the hopes that federal funding would help with those costs. Construction would likely last between three and four construction seasons.

Last night’s workshop presentation was the first in a series of events leading to an eventual decision on what to do with the stretch of highway. The Department of Transportation will hold a public input meeting about the project on July 13th. WHKS would have a final plan drafted in September for council review, with the hopes of then taking it to the Iowa Transportation Commission in October.