Traffic jams, lane closures and closed overpasses have become familiar to anyone commuting through northeastern Wisconsin as a result of the extensive Highway 41 construction project taking place from Oshkosh to Green Bay. The project, which is expected to be completed in 2017, is one of the most complex roadway construction projects ever undertaken in Wisconsin, and it will greatly improve the safety and efficiency of the most heavily traveled highway in the region. One of the improvements is the implementation of 40 roundabouts.
The roundabouts in the Highway 41 project will be constructed at the ramp terminals where vehicles enter and exit the highway, taking the place of traditional four-way t-intersections often regulated by traffic lights. Instead of approaching an intersection in which there is cross traffic, a roundabout is a circular intersection with flared entryways and a centerpiece that deflects traffic, causing drivers to slow down. All of the roundabouts on the Highway 41 project will be two lanes wide.
Andrea Bill, a transportation engineer working in the Traffic Operations and Safety Laboratory (TOPS Lab) at UW-Madison, studies traffic safety engineering and conducts several statewide safety tests and analyses for the Wisconsin Department of Transportation (DOT). Currently, Bill and her TOPS Lab colleagues are working on a research project analyzing roundabouts at ramp terminals.
At first, roundabouts seem foreign to drivers and can often cause confusion; Bill herself admitted to uneasiness the first time she encountered this new type of intersection as a driver. The Wisconsin DOT reports that only 22-44 percent of drivers are in favor of roundabouts before they are built, but one year after construction the percentage of drivers in favor of roundabouts increases dramatically to 57-87 percent. Why? A primary factor is safety. The circular intersection causes each vehicle to change its trajectory and, in the process, slow down. The intersection also forces all vehicles to move in a counterclockwise direction, reducing the feasibility of head on collisions.
A study conducted by the Insurance Institute of Highway Safety found that roundabouts result in a 90 percent reduction of fatal crashes compared to traditional t-intersections and that 76 percent of crashes in a roundabout result in less serious sustained injuries. With fewer conflict points and slower vehicle speeds, drivers and pedestrians are given more time to react. Although the TOPS Lab research project is still in its beginning phases, Bill is an advocate for the implementation of the roundabouts and the safety they provide, saying, “There may be crashes, but they’ll be a lot less severe. Although there may be people that have confusion [using the roundabouts], the confusion won’t be costing anyone their lives.” Current research also suggests that roundabouts are more efficient in facilitating traffic flow.
When approaching a roundabout, the driver must yield to all traffic coming from the left, as traffic flowing inside the roundabout has the right away. When there is a gap in the traffic flow from the left, the driver enters the roundabout by merging, just like the process of merging onto a highway from an on-ramp. According to TOPS Lab research, it typically takes a mid-size vehicle 3 to 5 seconds to merge, while a large truck, such as a semi, typically takes 5 to 7 seconds. Because there is no required stopping when using a roundabout, traffic can achieve a continuous flow. Problems emerge however, when drivers are unwilling to merge or there is a build-up of large trucks that need more time to enter the roundabout, but don’t have enough gap time. These problems are the primary focus of the TOPS Lab research.
“It’s about trying to find the balance between function and safety,” says Bill, “The goal is to get as many people as possible through while also making it safer. If you keep increasing the traffic you will see breakdowns; we’re looking at what kind of counter measures you can put in place so you don’t get backups on the freeways.” Bill is currently analyzing a roundabout in Jacksonville, FL, that also utilizes traffic light signals to help create sufficient gap times.
After the completion of the Highway 41 project, Wisconsin will lead the nation with the in number of roundabouts. “Other states are taking a slower approach, and the DOT realizes there’s a learning curve and is putting out several initiatives to educate drivers that will be using these roundabouts,” says Bill, “In an ideal world there would be a little bit more of an active outreach, but with budget constraints, that can’t always be done. Overall, what’s being done is great.”
The Highway 41 project and the construction of 40 new roundabouts is one of the most innovative transportation technologies being employed in the country. The studies of these new methods of traffic control are in their beginning stages, and the solutions to the problems are not yet discovered. Northeastern Wisconsin will be challenged with the implementation of these roundabouts in the future, but it will lead to safer intersections.