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Can we reduce crashes and avoid gridlock with geometry?

The intersection at Airline Highway and Siegen Lane-Sherwood Forest Boulevard in Baton Rouge, Louisiana, was notorious for long wait times and major crashes. Our client needed a solution, and fast. So, we traveled 1,800 miles (2,897 kilometers) to another country, and returned with an idea—the continuous flow intersection (CFI). This idea would solve everything.

Fewer accidents

The number of crashes at Airline Highway has been cut in half since the CFI was constructed.

Seconds in the queue

It used to take commuters about 4 minutes to turn left. Our design has reduced the wait time in the queue down to 30–40 seconds.

Two-legged CFI

Our Baton Rouge design is the first continuous flow intersection project ever constructed in the U.S.

Seeing is believing

Seeing is believing

The CFI design had rarely been used before in the U.S. So why this idea, and why now? Our project team thought it could work, but we had to see it first to believe it.

Our team jetted off to Tijuana and Juarez, Mexico, to see the continuous flow intersection “in action.” Our analysis of the CFI revealed that it was a better option than a traditional intersection on multiple levels—safety, operation, and cost. For instance, the CFI would only cost $5 million (US) versus the $50 million price tag for a typical grade separated intersection.

We were eager to bring this idea back home. When we returned, we visited the troubled intersection in Baton Rouge again and found a way to customize the CFI. Now we just needed to prove to the community that this foreign concept would work in our city, and show how millions of dollars could be saved in the process.

Transcript of the video follows
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<p>Our CFI design solves the problem between left-turning vehicles and oncoming traffic with a left-turn lane on the left side of the road. What the heck are we talking about, you ask?</p> <p>&nbsp;</p> <p>Let’s take a closer look. On a red light, left-turning traffic stops at the same time as traffic at the main intersection. When the light turns green for the left-turn lane, vehicles make their way to the intersection—and keep going. While they’re turning left, cross traffic is stopped at a red light and oncoming traffic starts to flow.</p> <p>Vehicles are still turning left. They’re just doing it well in advance of the intersection. By moving the left-turn action away from the main traffic flow and timing it with the signal cycle of the intersecting road, we’re reducing wait times and the risk of crashes. It may seem confusing at first, but turning left in a CFI isn’t so complicated—if you design it right.</p>
A traditional traffic signal controller is not meant to work at a CFI with 14 traffic signals. But we tricked it into working. Through coding and system design, we configured the signal controller to work with a CFI and maximize efficiency down to the second.

We’re better together

Our work begins at the intersection of community, creativity, and client relationships. With a long-term commitment to the people and places we serve, we have the unique ability to connect to projects on a personal level and advance the quality of life in communities across the globe.

Michael Bruce
Senior Principal
Michael Bruce
Senior Principal

With limited resources, innovative solutions in transportation has become a critical tool in improving quality of life.… Read More

Cindy Hall
Senior Associate
Cindy Hall
Senior Associate

I enjoy my job because I see the results of our solutions around the community; improving traffic flow and roadway safety improves lives.… Read More

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