Diverging Diamond Interchanges: A Safer Alternative to Left Turns

It is widely known that making left turns on the road is a particularly hazardous maneuver, particularly in areas with heavy traffic flow. We, as personal injury lawyers who specialize in truck and auto crash cases, understand the severe injuries that may be caused by accidents that involve left turns. However, there is a potential solution that could help reduce these risks: the diverging diamond interchange. Today, we’ll delve into the idea of diverging diamond interchanges and their potential to mitigate the risks involved with making left turns in conventional traffic.

The Dangers of Making a Left Turn in the Traditional Manner.:

Before discussing diverging diamond interchanges, let’s first consider the potential hazards of making a left turn. When making a left turn, drivers often must cross several lanes of oncoming traffic, which leaves little room for error. This type of turn comes with several hazards, such as:

Increased Risk of Collisions: When making a left turn, drivers may be at risk of colliding with oncoming vehicles, particularly if they miscalculate the speed or distance of the approaching traffic.
Visibility Limitations: Making a left turn can be challenging for drivers as they need to estimate the speed and distance of oncoming vehicles using their peripheral vision. Unfortunately, visibility can be compromised due to obstructed views, blind spots, or unfavorable weather conditions, potentially leading to accidents.
Time Constraints: When making a left turn, drivers often have a limited time window due to traffic signals or oncoming traffic. This can cause some drivers to feel rushed and take unnecessary risks.

Introducing the Diverging Diamond Interchange:

The concept of Diverging Diamond Interchanges (DDIs) is a recent development in transportation engineering, aimed at improving intersection efficiency and safety. DDIs are different from traditional interchanges in that they temporarily move traffic to the opposite side of the road. This creates a “crisscross” pattern that makes left turns easier and safer than traditional methods. Some key features of DDIs include:

Crossover Points: Designated crossover points are used to shift traffic to the opposite side of the road, effectively eliminating the need for left turns across oncoming traffic.
Dedicated Turn Lanes: DDIs have designated lanes for left turns at crossover points, providing a clear separation between vehicles turning left and those going straight.
Traffic Signal Optimization: Traffic flow is made smoother, congestion is reduced, and the risk of conflicts between vehicles is minimized by DDIs through the use of well-coordinated traffic signals.

Advantages of Diverging Diamond Interchanges:

Enhanced Safety: One of the main benefits of DDIs is their capacity to increase safety, especially when making left turns. By avoiding the need to turn left across oncoming traffic, DDIs effectively diminish the chances of accidents and lessen possible clashes between vehicles.
Improved Traffic Flow: By reducing the number of signal phases and allowing left-turn movements simultaneously, DDIs optimize traffic flow. This efficient design enhances overall intersection capacity and reduces congestion, resulting in shorter travel times for motorists.
Pedestrian-Friendly Design: Dedicated pedestrian paths and crosswalks are often included in DDIs to provide safety and convenience for pedestrians. The decreased vehicle conflict points and simplified traffic flow create a more effortless pedestrian experience while navigating through the interchange.

Case Studies and Success Stories:

Let’s talk about some real-life examples to illustrate the possible advantages of DDIs:

Springfield, Missouri: The first DDI in the United States was implemented in Springfield, Missouri. It has been extremely successful in reducing accidents, improving traffic flow, and increasing driver satisfaction. Additionally, there has been a significant decrease in left-turn-related incidents since its introduction.
Salt Lake City, Utah: The introduction of a DDI at the I-15/7200 South intersection in Salt Lake City has led to a significant decrease in traffic congestion, enhanced intersection capacity, and improved safety. The triumph of this initiative has encouraged further examination and implementation of DDIs in the surrounding area.

Considerations and Challenges:

Although diverging diamond interchanges can provide significant advantages, it is crucial to recognize the difficulties and factors involved in their execution. Here are some of them:

Costs of Construction: In order to build a DDI, it is usually necessary to make major changes to the infrastructure, such as realigning bridges and roadways. The construction process can be quite intricate and expensive, which means that it requires thorough planning and budgeting.
Driver Familiarity: The implementation of DDIs requires a deviation from the conventional intersection designs, and it might require some time for drivers to adjust to the new traffic patterns. It is essential to have adequate signage, conduct public awareness campaigns, and provide driver education to ensure a seamless transition and make the most of the advantages that DDIs offer.

What is the difference between a DDI and a Displaced Left Turn?

In a previous blog post, we discussed another departure from traditional left turns: the displaced left turn (DLT). The diverging diamond interchange may sound like the displaced left turn, but there are some key differences.

A DDI is a unique intersection design where traffic lanes temporarily shift to the opposite side of the road at the interchange. This innovative design enhances traffic flow and minimizes potential collision areas in comparison to conventional diamond interchanges. The DDI enables vehicles on the crossroad (usually an overpass or underpass) to briefly switch to the opposite side of the road, enabling unobstructed left turns onto the ramps without having to cross oncoming traffic.

On the other hand, a displaced left turn is a traffic design that moves the left-turn movement away from the main intersection. Drivers are directed to a separate lane or signalized intersection before or after the main intersection, instead of making a left turn directly at the intersection. This helps to improve safety by reducing conflicts with through traffic and simplifying the left turn.

While both DDI and DLT designs aim to enhance traffic flow and safety, they employ different approaches and are suited for different types of intersections. DDIs are typically used at freeway interchanges, while DLTs are often implemented at conventional intersections to improve left-turn movements.

One possible solution to the dangers of crossing oncoming traffic is by using diverging diamond interchanges, which offer a viable alternative to traditional left turns. DDIs can improve safety, traffic flow, and create a pedestrian-friendly environment by temporarily redirecting traffic to the opposite side of the road. While their implementation may pose challenges, the success stories from existing DDIs demonstrate their potential to improve intersection design and hopefully make our roadways safer for all users. However, it is extremely important that proper signage and road markings are implemented to reduce driver confusion which could ultimately lead to more collisions.