Missouri Route 13, U.S. Route 160, and Missouri Route 248 Roundabout Construction in Stone

How will the new intersection be different from the existing intersection?

A roundabout will be installed at this intersection and will include a truck apron to help trucks and trailers navigate the roundabout and will allow for longer vehicles to easily navigate the intersection.

What is the purpose of this intersection improvement?

This location has experienced an unusually high rate of severe crashes. The purpose of this project is to improve the safety of this intersection and minimize or eliminate high speed crashes.  As the agency responsible for the safe operation of these roadways, it is our responsibility to provide a solution that addresses the problem and provides lasting benefits to the system. 

Will the US Route 160, Missouri Route 13, Missouri Route 248, and Dogwood Tree Road intersection be closed during construction?

The U.S. Route 160, Missouri Route 13, Missouri Route 248, and Dogwood Tree Road intersection will NOT be closed during construction of the roundabout.  However, there may be times, of up to 15 minutes, that the roadway will be closed to allow for the contractor to move materials and equipment.

Why was a roundabout chosen for this intersection?

This location has experienced an unusually high rate of severe crashes.  The purpose of this project is to improve the safety of this intersection and minimize or eliminate high speed crashes.  A roundabout is the best solution for this location.  The configuration of a roundabout forces traffic to slow down and eliminates right angle crashes by directing all traffic in the same direction.  At the same time, roundabouts allow for a smooth flow of traffic and eliminate the unnecessary delays experienced at signals.

We have roundabouts throughout our 21-county district that are functioning well and providing the safety and traffic flow benefits we anticipated.  Other high-speed (55 mph or greater) locations include U.S. 60 and Route 43 near Seneca, Route 96 and Route 171 north of Carl Junction, Route 96 and Route 43 near Webb City, U.S. 166 at Downstream Casino, three locations along U.S. 160 in Willard and Route M at Repmo Drive (Republic High School).  We also have numerous locations on roadways with posted speeds below 55 mph, including urban areas and interstate interchanges.  These roundabouts are designed specific to each location, with some locations serving more truck traffic than others, but they all provide improved safety and traffic flow.

All the national studies and data show roundabouts to be the safer improvement.  Before and after studies based on multiple locations throughout the U.S. show that converting two-way stop-controlled intersections to a roundabout lead to an 82% reduction in fatal and injury crashes. Our experience with roundabouts in our own district has also shown that to be true. 

Why not install a traffic signal at this intersection?

This location has experienced an unusually high rate of severe crashes. MoDOT is working to eliminate signals along our high-speed routes, as the potential for severe crashes still exist at a signalized intersection and there is a history of severe crashes at many of these locations.  The potential for crashes at an intersection can be measured in the number of conflict points.  Conflict points are locations within the intersection where vehicles could crash due to conflicting movements. There are more than 30 conflict points at a typical signalized intersection.  All of these represent potential crashes and many being the crossing type that can result in severe crashes.  Motorists need to only be distracted for a short time or make a poor decision for a severe crash to occur.  

In contrast, roundabouts with 4 legs have only 8 conflict points.  Typical crash types at a roundabout would be rear end or side swipe.  This type of crash is not typically severe, especially at the slower speeds created by the roundabout configuration.  The potential for severe crashes is almost completely eliminated, as crossing conflicts are no longer possible. 

Signals increase the delay of the travelling public due to a signal's cycle time. Roundabouts allow for a smooth flow of traffic as the approaching vehicle does not have to come to a complete stop unless there is already a conflicting vehicle inside the roundabout’s circle.

Isn’t the speed of Route 160 and Route 13 too fast for a roundabout?

We have roundabouts throughout our 21-county district that are functioning well and providing the safety and traffic flow benefits we anticipated.  Roundabouts at high-speed (55 mph or greater) locations include U.S. 60 and Route 43 near Seneca, Route 96 and Route 171 north of Carl Junction, Route 96 and Route 43 near Webb City, U.S. 166 at Downstream Casino, three locations along U.S. 160 in Willard and Route M at Repmo Drive (Republic High School). These roundabouts are designed specific to each location, with some locations serving more truck traffic than others, but they all provide improved safety and traffic flow.

How will a roundabout help relieve the traffic backups that occur during certain months of the year? 

Signals increase the delay of the travelling public due to a signal's cycle time. Roundabouts allow for a smooth flow of traffic as the approaching vehicle does not have to come to a complete stop unless there is already a conflicting vehicle inside the roundabout’s circle.

Can 5th Wheelers, RV’s and boats use a roundabout?

Each roundabout is designed specific to each location, with some locations serving more specific types of traffic than others, but roundabouts provide improved safety and traffic flow for all types of vehicles, including recreational vehicles. Special design considerations are used when we know that we’ll have larger vehicles and truck with trailer combinations utilizing these intersections. One example is transversable truck aprons around the center island to allow the larger vehicles to off-track, if needed, while maintaining slower speeds for typical passenger vehicles as they travel through the roundabout. 

What is the cost of a signal compared to a roundabout?

The cost to build a roundabout is approximately $1.5 million. The cost to install a signal is approximately $1 million, however, we must also consider the cost to maintain a signal. In an average year, it is estimated that we spend around $9,200 per signal to operate and maintain it. The life of a signal is about 30 years before it needs to be completely replaced. Due to inflation, that $9,200 cost per year will increase. Using a conservative inflation rate of 3% per year over the 30-year period, we will spend over $400,000 just on maintenance of the signal. This cost does not include the pavement, pavement marking, or intersection lighting that we would also have to maintain but would be similar to the maintenance of a roundabout.

The purpose of this project is to improve the safety of this intersection and minimize or eliminate high speed crashes.  As the agency responsible for the safe operation of these roadways, it is our responsibility to provide a solution that addresses the problem and provides lasting benefits to the system. Thus, short-term costs are justified by the long-term safety goals of this project.