(Photo by Stina Sieg - KJZZ)

Vehicles backed up on the Happy Valley exit of I-17.

Heavy traffic on I-17 that runs past Prescott becomes inevitable on the holiday weekends, and Arizona Department of Transportation is working on a way to speed traffic flow by adding lanes.

The idea is to add two reversible lanes down the middle of I-17. Not the kind you would see in downtown Phoenix where both sides can access it.

Instead, the lanes could open for northbound traffic on a Friday, then switch to accommodate southbound traffic on Sunday.

ADOT spokesman Tom Herrmann says it will still take around six or seven years to be fully implemented

“We’re still a ways out from this happening, this isn’t going to help us on Fourth of July weekend or Labor Day, but for the long term it’s something that can help us quite a bit,” he said.

The lanes would also be used to help clear major crashes.

While still in the design phase, the lanes would stretch about eight miles, from Black Canyon City to Sunset Point rest area.