I'm not sure if I can really see the merit of this. Wouldn't the lanes just get backed up at either end due to the fact that they are merging down from four lanes to two? I don't know if there's steep grades or what, but it seems like adding a climbing lane would be a better solution here.
Yes, this is on a very steep and curvy section of I-17. There are a variety of issues on this section of roadway.
First, in either direction, whenever there's an accident it's an absolute clusterf*** of a situation. The only other alternative routes between the mountain plateau of Arizona and the Phoenix valley are SR 87 or SR 89/US 60. Both detours are probably hundreds of miles in length and add hours to the trip. It absolutely cripples travel to Northern Arizona whenever there are serious accidents involving fatalities or large clean ups.
Second, especially on the weekends (Friday NB, Sunday SB), the volume of traffic is absolutely massive. It's packed, bumper to bumper. Then you throw in the semi-truck traffic, and it just ends up being a complete mess. You have trucks barely getting up the hill at 20 mph, drivers who are too timid to pass anyone, and others trying to Mario Andretti their way up the hill. Going down is the same thing, four wheelers (to use trucker lingo) cutting off semi's and just causing traffic chaos.
I'm torn on the reversible lanes idea. On one hand, I think adding a climbing lane to the NB side would make a massive difference simply because of the grade and the semi truck traffic. But it doesn't solve the accident problem. But if you go with the reversible lanes, then you get the bottleneck problem at the re-entry end of four lanes going down to two. Perhaps they could look into adding a third lane from Black Canyon City down to Anthem (which I personally think is needed today) to cut down on the SB re-entry problem, but NB you would have the bottleneck.
So honestly, I'm not sure what I think of this. And also, what is the cost and timeline for this? ADOT did a briefing a couple weeks ago on some highly-needed projects on AZ 89 between Chino Valley and Paulden, and they said 25 years and $60 million dollars. I can definitely say the terrain would require very little altering. But these reversible lanes would require an astonishing amount of blasting. Just take a look at this video and look at the terrain. The proposed reversible lanes would be to the left of the existing lanes in this video.