First off here's a little piece on US 191X. I'm pretty sure there's a lot of people that already know about this. I want to put this post out there for those who aren't familiar with it and I want to discuss this anomaly and technicality as I think it's interesting. The topic is US 191 around Morenci being discontinuous. ADOT defines US 191 in both maintained mileage and the state-recognized designation as being discontinuous from just northwest of Morenci at milepost 173.00 to the intersection of US 191 and Zorilla Street in Morenci proper. The route in between, while recognized as US 191 by AASHTO, is not recognized as mainline US 191 by ADOT. Instead, ADOT places a bannered route in its location. Internally referred to as US 191X and by Arizona Transportation Information System (ATIS) code as UX191, this section of the old highway, cutting through the open-pit mine in Morenci is signed and referenced in the field as US 191 Temporary (US 191T). Anyway, back to US 191 through Morenci. The plan, as I understand, is to eventually build a new more modern alignment that bypasses the pit altogether, which has been on the backburner for several years. Though I would not be surprised if this project stayed on the back burner for the next decade. ADOT has trouble widening US 93 to four lanes without delays, let alone actually getting around to rebuilding US 191 in a very remote area of the state. So, that said, what's everyone's thoughts on the unusual anomaly that is US 191T/US 191X?
And now onto the main topic, the "X" suffixed routes. ADOT and several other government agencies use the Arizona Transportation Information System (ATIS) coding and terminology when discussing or listing highways in Arizona within planning and technical documents. Or at least that's the case with some agencies around Pima County and ADOT in regards to GIS data and State Highway Logs. The "X" suffix at the end of highway designations using ATIS or ADOT terminology actually means "Temporary", whereas the general road enthusiast public likes to use the suffix "T". US 191X (US 191T) is a prime example of an expected use of a temporary route, being temporary in the case of acting as the main corridor until the dedicated corridor is completed. US 89X (US 89T) is another example. The "X" routes in Arizona also have a second use, which is basically the same as the "U" routes in California: remnants of older state highways or highway routings that have never been abandoned/handed over to other jurisdictions. There's actually quite a few of these in Arizona.
The most well-known example is US 60X in Phoenix and Apache Junction, sections of the Pre-Superstition Freeway route of US 60 never turned over to local jurisdictions and still maintained by ADOT to this day.
US 93X in Wickenburg is another "X" route believe it or not. That route is Tegner Street between US 60 and current US 93. US 93X is, of course, the older route of US 93 prior to the interim Wickenburg bypass that US 93 now takes along the Hassayampa River around downtown.
US 93 has a second "X" route at the Nevada State Line. SR 93X. What's odd about this route is despite it being a spawn of US 93, it has a State Route designation, which means it's technically a section of SR 93. ADOT Highway Logs and GIS data confirm this. SR 93X is Kingman Wash Access Road, the original path of US 93 over the Hoover Dam, replaced when the Pat Tillman-Mike O'Callaghan Memorial Bridge was completed. So yes, ADOT still maintains the old section of US 93 going up to the Hoover Dam and over it and it has not been abandoned to the Federal Government or Mojave County.
A historic example of an "X" route is SR 85X, now known as MC 85, Buckeye Road, 17th Avenue and Van Buren Street. I'm sure everyone here is familiar with the SR 85/Papago Freeway story. Following the completion of the Papago Freeway and re-routing of SR 85 onto the former spur route, the path of SR 85X that had previously acted as US 80 to Grand Avenue, was redesignated SR 85X. This route actually shows up in the 1998 State Highway Log. SR 85X was gradually abandoned and handed over to local jurisdictions until the last section was given to the City of Phoenix in 2002.
And lastly, the infamous US 89T/N20 route, put into place following the landslide at Page, was internally designated US 89X.