Interstate 17 is the main north-south freeway in Arizona, connecting Phoenix with Flagstaff. It is a heavily traveled, regional corridor that connects Interstate 10 with Interstate 40.
Within Phoenix, I-17 travels the Black Canyon Freeway, one of the older freeways in the city completed in the early 1960s1. It leaves the urban area and enters the central Arizona desert, with a former business loop (decommissioned in 2011) serving Rock Springs and Black Canyon City.
Interstate 17 turns northeast and begins its ascent onto the Mogollon Plateau after the split of Arizona 69 toward Prescott at Cordes Junction. This requires a significant elevation increase between the desert floor and the top of the plateau, and the views are rewarding. I-17 traverses Coconino National Forest for its remaining distance to Flagstaff, with a forest landscape that is significantly different from the desert below.
The freeway has two major connections to the famous Sedona area, via Arizona 260 near Camp Verde and Arizona 179 near Rimrock. I-17 continues through national forest land until meeting I-40, and the freeway ends at an early 2000s-rebuilt cloverstack interchange. Arizona 89A (Milton Road) stems north from the freeway end as a surface street into the city center of Flagstaff.
Parallel U.S. Routes
The northernmost reaches of Interstate 17 replaced U.S. 89 Alternate. The remainder of the route replaced Arizona 69, to U.S. 89, which ran in tandem through Downtown Phoenix along side U.S. 60-70-80.
The Black Canyon Freeway, originally constructed in Phoenix between Jefferson Street and Northern Avenue with four lanes, was designed for 20,000 vehicles per day (vpd). As of 2003, the same highway carried up to 220,000 vpd amid six through lanes and two HOV lanes. The freeway is home to routine traffic back-ups.
Expansion options to mitigate traffic congestion along I-17 were included in the Maricopa Association of Government 20-year Regional Transportation Plan. Funds earmarked for Interstate 17 in the plan included one study to build an upper deck to the freeway. Inspiration for the I-17 plan was derived from the construction of a second deck for the Leroy Selmon Expressway (SR 618) in Tampa, Florida, in addition to the population density adjacent to the Black Canyon Freeway. This east-west tollway was expanded as part of a $350 million in construction between April 2004 and July 2006. Six miles of roadway were added for the use of reversiable traffic flow. These were supported with single pier-supports placed within the tollway median. Within Phoenix, the second deck of the Black Canyon Freeway was considered for the stretch between Interstate 10 (Exit 199) north and Dunlap Avenue (Exit 207), a distance of eight miles.
Similar to the Tampa roadway, the I-17 roadway would have carried Express lanes with only a few entry and exit points. Some early public comments on the project were positive. A west Phoenix community group, Community Leaders Organizing for Urban Transformation (CLOUT), however were not supporters. They contested that the highway would help divide west Phoenix from the rest of the city and advocated a relocation of funds toward mass transit-based projects. As of 2003, construction of the upper deck for Interstate 17 was unlikely until 2016 and 2020.1
No progress was made since and by 2011 a new I-17 Corridor Improvement Study was underway. This ADOT study was rescinded in 2012, along with the concurrent ADOT I-10 Corridor Improvement Study. Planning, engineering and environmental information derived from those studies were folded into a new I-10/I-17 Corridor Master Plan. Referred to as the “Spine”, because of its role as the backbone of transportation mobility in the Phoenix area, the study pertains to 35 miles of I-10 and I-17 from Loop 202 to the south and Loop 101 to the north. The first round of public meetings on the Spine Study were conducted by the Maricopa Association of Governments in partnership with ADOT and the FHWA in March 2015.
North End – Flagstaff, AZ
South End – Phoenix, AZ
Branch Routes – 0
Mileage – 145.76
Cities – Phoenix, Flagstaff
- Junctions –
Source: December 31, 2018 Interstate Route Log and Finders List
I-17 Annual Average Daily Traffic (AADT)
|Location||Vehicles per day|
|North Phoenix, AZ||14,099|
Source: 2001 Arizona Interstate Annual Average Daily Traffic (AZDOT)
Portions of Interstate 17 were open to traffic by 1964, including the Black Canyon Freeway in Phoenix and upgraded sections of Arizona 69 around Black Canyon and Cordes Junction. A super-two section of Arizona 79 bypassed Sedona. It was four-laned by 1976.
The Black Canyon Freeway opened first in 1958 at Grand Avenue (U.S. 60) and Thomas Road. Subsequent sections opened in 1960 north to Glendale Avenue (Exit 205) and 1961 from Exit 205 to Dunlap Avenue (Exit 207).
Interstate 17 between Phoenix and Cordes Junction (Exit 262), replaced the southern extent of Arizona 69. This is significant because the exit numbering scheme still follows the original mileage of Arizona 69. According to the Misc.Transport.Road FAQ (Marc Fannin) and based on comments from Richard C. Moeur, a unique milepost system was utilized in Arizona until the mid-1980s. The system specified that any route that did not enter Arizona from another state used the mileage of the intersecting route’s mileage at its south or west end as its starting value. The former route of Arizona 69 originated from U.S. 89 at milepost 201. Since I-17 & AZ 69 were overlapped originally, the exit numbers along the freeway used the mileposts of AZ 69. The exit numbers on Interstate 17 are not related to those of Interstate 19. 174 miles separates the respective south ends.
The Black Canyon Freeway was the first section of I-17 to be built, with construction opening segments from I-10 northward to Little Deer Valley between 1958 and 1965. The freeway was completed in 1978 when the road north from Exit 268 (Dugas Road) through Spring Gulch to Arizona 169 (Exit 269) opened to traffic. See the I-17 Arizona guide for the rest of the time line.
According to the journal Roads and Bridges in 2000, Interstate 17 could be considered for an extension described as follows:
Interstate 17 — Phoenix to Salt Lake City: Like Phoenix, Salt Lake City is one of the nation’s fastest growing metropolitan areas with a population of 1.2 million. There is no direct Interstate connection between Phoenix and Salt Lake City. Completion of this corridor would require building or upgrading approximately 300 miles of roadway from Flagstaff, Arizona, to Sevier, Utah.
I-70 and I-15 would complete the connection to Salt Lake City. The costs to construct a new terrain route between Flagstaff and southern Utah, both economic and environmental, would be significant.
North End – Flagstaff, Arizona
South End – Phoenix, Arizona
- “Double deck urged for I-17 in Phoenix.” The Arizona Republic, September 16, 2003.
- “$15.7 billion transit plan endorsed.” The Arizona Republic, September 18, 2003.
Page updated July 6, 2015.