Navigating the Diverging Diamond Interchange

Navigating the Diverging Diamond Interchange


[♫ Upbeat Music ♫] At the Iowa DOT, we think outside the box and use interchange designs that may be unfamiliar here, but have been tested in other places to help solve transportation challenges. These solutions might feel a bit unusual to the user at first – that’s expected. However, with a little bit of knowledge, some patience and practice, navigating these “new to Iowa” solutions will bring a variety of benefits. In Iowa, we are beginning to utilize Diverging Diamond Interchanges, sometimes referred to as DDIs, and you may have some questions. This video will help explain how Diverging Diamonds work, how to drive them, and how the design benefits the traveling public. A Diverging Diamond is a design solution that in certain locations, will improve safety and mobility when compared to a traditional interchange. On average, the Diverging Diamond features fewer opportunities for crashes. And when crashes do occur, they are typically less severe. So how does a Diverging Diamond function? Drivers still make right turns as they would in a traditional interchange. The biggest difference in this interchange design is how the left turn is handled. Traffic transitions from the right side of the road to the left side of the road and then back again. Because traffic is on the left hand side of the road, left turns occur without having to cross oncoming traffic. Signs and pavement markings work together to make this simple and intuitive for the driver. The key to driver ease is focusing on the directions provided. Let’s get on the road and try a Diverging Diamond out where traffic crosses over to the left side of the roadway between interchange ramps. [♫ Upbeat Music ♫] Once you’re on the left side, you can turn left onto the ramp without stopping and without crossing in front of oncoming traffic. See, it’s that simple! Diverging Diamond benefits include improved safety, increased mobility and enhanced operations, as well as has the potential to require less property. First, Diverging Diamonds eliminate conflicts where traffic crosses, resulting in the potential for incidents. Eliminating these conflicts works to reduce the number and severity of crashes. The second major benefit of a Diverging Diamond is how they improve mobility by operating more efficiently. Diverging Diamonds work well in comparison to traditional interchanges where there is heavy traffic. They accommodate more vehicles because all turning movements can be free-flowing. Stops may only be necessary for those traveling through the interchange. Finally, Diverging Diamonds may require a
smaller footprint than other interchange types, which could result in fewer impacts to surrounding properties. You might also be wondering about the impact a Diverging Diamond may have on pedestrians and bicyclists in the area. Good news! Safe and convenient pedestrian walkways and crossings are important components of any well-designed interchange. At a Diverging Diamond, pedestrian walkways are commonly located either through the median or along the sides of the crossroad, while dedicated bicycle lanes may be placed to the right of traffic. However, every situation is unique and we work to meet the needs of the community for each project. The Iowa DOT continues to bring innovative solutions to the state. Transportation improvements are built using a variety of tools. We’ll choose the most appropriate tool from our toolbox to meet the transportation challenge at hand. [♫ Upbeat Music ♫]

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