Interchanges are inherently difficult areas for creating safe and efficient road systems. They often feature high traffic speeds and increased traffic volume moving through multiple intersecting lanes.
Conditions can become especially dangerous when one direction of traffic has to cross over the path of oncoming traffic flow. Left turn lanes, which are regularly found in more traditional interchange systems, put drivers at a much higher risk of high-speed accidents. Reducing the number of these vehicle-to-vehicle conflict points is the primary feature of a diverging diamond interchange (DDI); DDIs reduce these conflict points by nearly 50%.
While DDIs have been a highly successful innovation in traffic safety, the nature of right-lane traffic temporarily crossing over to the left lane can be confusing for drivers. In-road warning lights used to line the lanes at crossover points are an excellent way to improve driver confidence when moving through the intersection.
DDIs feature a number of benefits, from safety to cost of construction to efficiency and capacity. In a retrofit, when compared to a more traditional interchange system, construction time is reduced and additional right-of-way sections are rarely needed. A new interchange requires fewer lanes, less bridge structure and is overall far less costly, with savings of up to 75% versus a traditional system.
Wrapping your head around the functionality of a DDI system can feel a bit confusing at first glance. The following video showcases how crossover points and the elimination of vehicle-to-vehicle conflict turns set the DDI apart from traditional systems.
Diverging diamond interchanges have been the focus of a number of studies since the first DDI in the USA was constructed in Springfield, Missouri in 2009. There are currently over 100 functioning DDIs in the USA, with 100 more in the planning stage.
In the case of this first DDI in Springfield, Missouri, the project was called a “huge success” in a follow-up document. Two years later, a study on this DDI was published that highlighted three distinct improvements: traffic operation, safety, and public perception.
Transferring to the left side of the road, even for a brief period, can make drivers feel like they may be putting themselves in a position for a potential wrong-way accident. To reduce this confusion, in-road warning lights can be used as a lane guidance system. In-road warning lights delineate the lanes and are connected to the overhead regulatory lights through a LaneLight system controller. When the light turns green, the in-road warning lights are automatically activated, prompting motorists to move through the intersection.
In-road warning lights feature:
As cities grow and population levels increase, adjusting the traffic systems we implement to focus on both safety and efficiency has become a vital consideration. DDIs have been shown to make large improvements over traditional interchange systems by employing an innovative lane crossover system.
While this system is clearly beneficial, it can prove hazardous when drivers do not understand how to safely move through it. In-road warning lights are an excellent addition to any DDI, especially when visibility is low or when there is a history of wrong-way driving.
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