Insights

Combat Long or Dangerous Drives with Innovative Intersections

You embark on your evening commute after a long day of work – and it seems the rest of the world is on the road too. Waiting to turn left, you watch cycle after cycle of left-turn arrows appear and vanish as you slowly inch closer to the intersection. Eager to see your family, eat dinner and relax, you feel frustrated that an act as simple as your drive home can take so much time and energy. “There must be a better solution,” you think. After what feels like a lifetime, you finally take your turn through the intersection and make your way home.

Operational inefficiencies at traditional intersections, like this one, become more common as traffic volume increases. Non-traditional, or innovative, intersections can help communities combat these issues and improve safety. These intersections may look unusual compared to the cross-shaped ones we see daily, but they can have significant benefits. 

Two of B&N’s experts share their perspectives on innovative intersection design.

Q: What makes an intersection “innovative”?

Molly:

In this context, innovation means putting a spin on your roadway geometry and signalization to create a design for a space where a traditional intersection typically wouldn’t fit or operate well. 

Innovative intersections may also chain multiple types into one or restrict certain movements. For example, a roundabout eliminates the left-turn movement that causes most of the injury crashes at a traditional intersection. Since the left-turn movement doesn’t exist in a roundabout, injury crashes are a rarity.

Other types of intersections are innovative because they incorporate grade separation. These intersections, such as the diverging diamond interchange (DDI), echelon intersection and single-point urban interchange (SPUI), increase efficiency and safety by isolating movements.

Jason:

Depending on where you are in the country, some intersections may seem more innovative or nontraditional than others. Here in Arizona, we see many SPUIs, so those may not seem “innovative” to a resident. Similarly, Missouri led the implementation of the DDI, Michigan is known for the indirect left-turn corridors.

However, innovative intersections include any intersection beyond a traditional signalized intersection with throughs, left- and right-turns in the same location. Often, left-turns affect the efficiency of an intersection, so many of the innovative intersection designs displace left-turns to increase efficiency and safety.

Q: How does an innovative intersection benefit a community?

Molly:

The goal is always to get you to your destination safely and efficiently. Innovative intersection designs can decrease the number of conflict points in an intersection for vehicles and pedestrians, resulting in less potential for crashes and injury.

They also benefit a community by increasing operational efficiency. Alternative signal configurations, or designs with continuous flow for certain movements, can prevent delays in an intersection and get you to your destination more quickly. As communities grow, these intersections allow them to address the increased traffic volume in a new way while either remaining within the existing footprint or limiting right-of-way acquisition.  

Jason:

Innovative intersections are developed to be more efficient: you can push more traffic volume though by altering the left-turn movement. They also present an opportunity to address and balance multiple safety concerns, such as bicycle, pedestrian or transit.

Often, the area surrounding an intersection is already developed, so there isn’t land available for additional lanes. Innovative intersections can be a solution to process greater traffic volumes safely while maintaining a smaller intersection footprint.

In Arizona, we have very large intersections where a pedestrian crossing can take a long time. Innovative intersections can help reconfigure pedestrian crossings and signalization so that can cross time is shorter and safer. These designs can also reduce potential conflict points with pedestrian and bike facilities, increasing safety for all users.

Q: What do you consider before implementing an innovative intersection?

Molly:

We take a holistic approach when considering an innovative intersection, including site history and traffic data, safety and cost-benefit analysis. Our team remains abreast of the designs and trends, so we can keep a “toolkit” of innovative options when analyzing an area and find the optimal solution for the client. 

We also consider stakeholder buy-in before choosing to implement an innovative intersection. Client education is crucial to gain their support and obtain leadership buy-in. Then, we consider public perception and education. New or unique configurations can be confusing or intimidating to the public, so it is important to have an intentional and effective public involvement and education program. Community support helps ease the implementation of the project.

Jason:

We always consider the constraints in the surrounding areas before determining what intersection is ideal. These constraints could be physical or environmental, such as a railroad or existing businesses, and prevent expanding the right-of-way. When you are constrained to remain within a certain footprint, but still need to get more traffic through a corridor quickly, you must get creative with the design and that is when we would consider an innovative intersection. Budgetary constraint is another factor, so we always aim to do “more with less” through our designs.

Stakeholder input is a necessity. Before implementation, you need to consider if you have agency buy-in and support from leadership. To help, we have conducted focus groups to gauge public perception and test design feasibility. Once a design is selected, we continue public outreach with in-person workshops or social media campaigns to help introduce an innovative intersection to the community.

Q: What are the current trends for innovative intersections?

Molly:

In the past decade, there has been a big increase in roundabouts in the United States. The public is becoming more comfortable driving through them, and some communities are even taking a roundabout-first approach over a traditional intersection. Roundabouts keep traffic moving, improve safety and are aesthetically appealing – all benefits that have encouraged wide-spread acceptance.

DDIs are another type that is popping up across the country. B&N helped Ohio and Indiana implement the first DDI in each state. Similarly, the Idaho Transportation Department (ITD) is exploring innovative intersections, such as continuous flow intersections (CFIs), for some of their high-capacity intersections with right-of-way constraints. As the state’s population continues to grow, I expect ITD and other local jurisdictions will look to more unique solutions like this one to alleviate congestion. 

Looking farther into the future, I think we will continue to see more innovative intersections implemented as communities become more comfortable with the various configurations. I anticipate that communities will standardize their specifications and put their unique local spin on their design and operation. 

Jason:

One trend is communities customizing intersections based on local values. In Tucson, for example, the local preference is to maximize the capabilities of major streets through innovative intersections, instead of building new major roadways like a freeway. They implement innovative intersections along corridors to increase efficiencies.

Different regions are advancing in different ways based on local values and needs. What may be “run-of-the-mill” in one geography could be unfamiliar or an emerging trend in another. For example, the median U-turn is well-established in Michigan but has been introduced in Arizona as the “Arizona Parkway.” Contrarily, the first DDI in Arizona is going to open soon, even though they are growing in numbers in other states. I anticipate that DDIs will become more common in Arizona because of their efficiencies, safety improvements, and cost-saving potential.

Watch the video below for a visualization of intersections discussed. Learn more about B&N innovative intersection and roadway experience here.

Molly Loucks, PE, Transportation Engineer
Molly Loucks, PE
Transportation Engineer
Jason Pagnard, PE, Senior Project Manager
Jason Pagnard, PE
Senior Project Manager