The state Department of Transportation is considering the possibility of using reversible lanes on a windy stretch of Interstate 17 in hilly north-central Arizona to reduce traffic backups from crashes, congestion and other circumstances.
ADOT said it is spending $3 million for preliminary design work on alternatives for the eight-mile stretch between Black Canyon City and Sunset Point and that an additional $5 million is set aside for final design work several years down the road.
I-17 is the main route between Phoenix and Flagstaff, and traffic often slows dramatically on weekends as Phoenix-area residents head to or return from the high country.
Detours are difficult much of the way because of rugged terrain and lack of alternative routes, and miles-long backups are common due to serious accidents at the start or end of holiday weekends.
ADOT has posted an animation showing a possible arrangement for adding reversible lanes between Black Canyon City and Sunset Point for southbound or northbound traffic to use as needed.
However, spokesman Steve Elliott said Friday whether and how the reversible lanes would be added hasn't yet been determined.
Construction costs for adding reversible lanes are preliminarily estimated at $125 million, ADOT said in a statement.
"While no funding is currently available for a reversible-lane system or widening projects, ADOT is aggressively seeking solutions including the possibility of a public-private partnership that could move a large project along sooner and at a lower cost," the agency said.
ADOT has said it would like to widen I-17 to a total of six lanes from the current four for the approximately 45 miles between Anthem in north Phoenix and Cordes Junction, a stretch that includes the eight miles between Black Canyon City and Sunset Point.
In the short term, ADOT plans this year to add new signage on I-17 north of Phoenix to help promote safety.
The signs will include displays of vehicles' speeds and message boards to display safety messages and information about highway conditions.
Watch video of how the alternating lane setup would work below: