North Carolina is among a growing number of states that have added their first continuous flow intersection.
The N.C. Department of Transportation recently announced the opening of the state’s first such intersection – also known as a displaced left turn intersection or crossover displaced left turn intersection – at N.C. 16 and Mount Holly-Huntersville Road in west Charlotte.
All main through traffic approaching the continuous flow intersection (CFI) stays the same, but left turning traffic heads into separate lanes several hundred feet before the intersection. The left lanes cross lanes of incoming traffic at a traffic signal and are then sent wider to the left of the incoming traffic to make left turns at the intersection. To watch an NCDOT video of the CFI, see below:
A growing alternative
NCDOT says the design will move more traffic through the intersection to reduce congestion.
Other states have been using the design, created in Mexico, including such early adopters as New York (1995), Maryland (2001), Louisiana (2006) and Utah (2007).
The Florida DOT opened the state’s first CFI in July in Lee County. And the Georgia DOT opened its second one this summer in Snellville. Its first was in Dawson County in 2017.
The engineer for the most recent Georgia CFI, Gresham Smith, said the design shaved $10 million off the cost of deploying a full-grade separated solution. The construction schedule was set for two years instead of three to five with a full-grade solution.
The Federal Highway Administration cites the following advantages of a CFI in its “Alternative Interchanges/Interchange Information Report”; April 2010:
- Lower cost and faster construction than a grade-separated interchange.
- Fewer conflict points than a conventional interchange, which improves safety.
- Potential to considerably reduce average intersection delays.
The FHWA also lists some potential disadvantages:
- CFIs require more space than conventional intersections, which could be a problem in areas where right of way is limited and costly.
- They can restrict access to parcels within their quadrants.
- U-turns may have to be eliminated.
- CFIs can be confusing for pedestrians. FHWA recommends use of pedestrian signals.
- An internal conflict point is created at left-turn crossover points.