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What is the Continuous Flow Intersection?

The first Continuous Flow Intersection is coming to Florida, to be built in the Fort Myers area.  Like many growing metro areas, Fort Myers is in need of many intersection improvements.

What is the continuous flow intersection?

Unlike the Diverging Diamond Interchange, the Continuous Flow Intersection is an at-grade junction of two roads.  In some areas, the intersection is also known as a Crossover Displaced Left Turn.

The most notable feature of the intersection is the left-hand turn lanes. A good candidate for a conversion of this interchange is a road with lots of left-turn traffic combined with thru (straight) traffic, simultaneously in both directions.

Continuous Flow Intersection
GIF showing the light cycle of green, yellow, and red lights.

The YouTube video above shows a proposed Continuous Flow Intersection at State Road 82 and Daniels Parkway in Fort Myers, Florida.  When it opens, it will be Florida’s first such interchange.

The first intersection of this type was built in Haddon Township, New Jersey over 20 years ago.  It eliminates long turn cycles, combined with allowing thru-traffic to flow more smoothly.  This intersection is a hybrid of a standard Continuous Flow Intersection, though the flow of traffic is improved.  Notice the right-hand turn previous to the left-hand turn going from north to west.

A more traditional type of this intersection was built in 2006 in Baton Rouge, LA

Another such variation of exists in Sarasota, Florida at the intersection of Fruitville Road and Sarasota Center Boulevard.  Known as a jughandle intersection, it starts out as a right hand turn before making a 180-degree turn north.  Sort of a trumpet interchange without an overpass.

Since 2000, over 40 such intersections have been built in the United States.  They currently exist in 13 states, the northernmost intersection being on New York’s Long Island.  Continuous Flow Intersections exist in Mexico, Australia, United Kingdom, and Germany.

What are the Advantages?

  • Plenty of room for cars making a left hand turn, by expanding the left turn lanes and segmenting them into two portions.
  • Fewer conflict points in the intersection mean green light cycles can be longer.  A conflict point is any point where cars can make initial impact in a collision.
  • Right-turning cars avoid traffic altogether until they merge 100 or more feet down the road, again, eliminating conflict points.
  • With bike lanes provided, there is easier navigation for bicyclists than an intersection such as a Diverging Diamond.  Longer light cycles give more time for bicyclists to clear an intersection.

What are the Disadvantages?

  • Left turners would have to go through two lights.  The first light a few hundred feet before the intersection, and the second light at the intersection.
  • Businesses on the right side of the road after the intersection are impossible to reach to thru traffic.  Such as in Baton Rouge, a secondary access road would have to be provided.  A lone point of access would have to be several hundred feet beyond the intersection, cutting across right-turning traffic.
  • Difficult to build unless the intersection has plenty of right of way width.
  • Walkability can be difficult, requiring stops at as many as four points in one direction.  A traditional intersection rarely has more than one stop required.

Adjustments to Existing Intersections

  • A significant right-of-way acquisition on the primary road.
  • Re-striping of lanes and crosswalks.
  • Re-timing and re-positioning of lights in the intersection
  • Addition of lights away from the intersection.
  • New signage both away from the intersection and at the intersection.
  • Additional signs prohibiting right-hand turns on a case-by-case basis.

Is it Worth It?

In short, no.

Simply adding a left turn lane as an option lane to the inside thru lane would be a more simple aternative.  Additionally, lights would need to be re-timed to where northbound traffic can never go at the same time as southbound traffic.

This would allow longer single-direction light cycles and more left hand turns in a single light cycle.

Below is an intersection that allows one direction of travel at a time, but unlimited turns.  Red lines represent stopped traffic.

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