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ADOT I-17 Improvement Project

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Flex Lanes

The first flex lanes on Arizona’s state highway system are coming to Interstate 17 in 2025 as part of the I-17 Improvement Project. The flex lane system is a proven technology to safely address traffic congestion during peak travel times, or if an unplanned incident creates delays.

The flex lanes, which will run adjacent to the existing southbound lanes for approximately eight miles between Black Canyon City and Sunset Point, will be an additional two-lane roadway that carries one direction of traffic at a time and can alternate between north- and southbound directions during peak travel times, or if there is a crash or another emergency situation that causes traffic delays.

Typically, the flex lanes will be open to northbound traffic Monday through Saturday, and open to southbound traffic on Sunday. However, the flex lanes will open, as needed, to whichever direction has the heaviest traffic. The flex lanes will be operational seven days a week.

Flex Lanes Safety Measures

Swing gate system
Swing gate system

To maintain safety for all drivers, the flex lanes will be separated from the existing southbound lanes by a concrete barrier. Vehicles will use new crossover lanes to access the flex lanes. The two flex lanes will allow traffic to move either northbound or southbound, depending on the greatest need. Dynamic overhead guide signs will alert drivers to the open direction of the flex lanes.

A specialized, automated net barrier and swing gate system at both ends of the flex lanes will be used to prevent vehicles from entering the flex lanes when traffic is flowing in the opposite direction.

When the flex lanes are closed, the swing gates will be extended and the net barrier will be in the down position, preventing vehicles from entering the flex lanes from the wrong direction.

Flex Lane Closed sign

The ADOT Traffic Operations Center will control the gates and net barriers remotely and will monitor the flex lanes with cameras placed throughout the eight-mile flex lane corridor. In addition, dynamic overhead guide signs will alert drivers whether the flex lanes are open or closed in the direction they are traveling.

Steel Gates in the Concrete Barrier

Emergency Lane swing gate
Emergency Lane swing gate

Steel gates will be installed in the concrete barrier at four locations throughout the eight miles of flex lanes to allow emergency responders to clear traffic out of the flex lanes and into the general purpose lanes in the event of an incident. The gates are approximately 30 feet long and can be opened in either direction.

Other U.S. Cities That Use Similar Flex (Reversible) Lane Systems:

  • I-5 Express Lanes (Seattle, WA)
  • I-90 (Seattle, WA)
  • I-25 Central Express Lanes (Denver, CO)
  • I-394 (Minneapolis, MN)
  • Reversible Express Lanes (Tampa, FL)
  • State Route 75 San Diego-Coronado Bridge (San Diego, CA)
  • I-35E and US 67 (Dallas, TX)

Other Flex Lanes Info

  • The speed limit in the flex lanes will be 65 mph once they are completed and open to the driving public.
  • Flex lanes will not be limited to High Occupancy Vehicles, and there will be no vehicle restrictions in the flex lanes. State laws prohibit ADOT from restricting commercial trucks from using the flex lanes. However, signage will recommend that slower-moving vehicles stay in the general purpose I-17 lanes.
  • There will be no tolls for the flex lanes.

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