Interstate 19 connects Nogales and Mexico with I-10 and Tuscon in southern Arizona. The freeway curves west around Crawford Hill from Grand Avenue (old U.S. 89) and the international border to bypass Downtown Nogales north to Arizona State Route 189. North from Rio Rico, I-19 parallels the Santa Cruz River to Tubac, Green Valley and the south suburbs of Tucson. The lone six lane section joins SR 86 with I-10 at South Tucson.
Costing $54.2 million, the Ajo Way Traffic Interchange project got underway in March 2016. Completed in Spring 2018, Phase I rebuilt the six-ramp parclo exchange with SR 86 and Ajo Way into a single point urban interchange (SPUI). Additional work added sound walls along I-19 from Ajo Way south to the Michigan Avenue pedestrian bridge. Started in July 2018, Phase II of the project expands southbound I-19 and constructs a braided ramp system between the Irvington Road off-ramp (Exit 98) and Ajo Way entrance ramp. Work on I-19 northbound adds an auxiliary lane from Irvington Road to SR 86 (Exit 99), sound walls, and a new pedestrian bridge at Michigan Avenue. Project II will take 18 months to complete and costs $29 million.4
High Priority Corridor
Interstate 19 from Nogales to Tucson is part of High Priority Corridor 26: CANAMEX Corridor.
Parallel U.S. Routes
Interstate 19 ultimately replaced the original route of U.S. 89. Some old segments of U.S. 89 at Tucson and Nogales were incorporated into Business Loops for I-19. The Tuscon business route was eventually decommissioned.
Interstate 19 opened initially from Rico Rico Drive (Exit 17) to Palo Parado Road (Exit 25) in 1966. The freeway was completed in 1979 when the section from Tubac (Exit 34) to Chavez Road (Exit 40) opened to traffic. See the I-19 Arizona guide for the rest of the time line.
One of the unique features of Interstate 19 is that the exit numbers and distance signs are based on the metric system, a first for the U.S. Interstate system. The use of metric units along I-19 was the result of a President Carter administration pilot project aimed to have the United States adopt the system. The metric units also served as a hospitality measure for Mexican tourists headed north to Tuscon and Phoenix.
Some of these metric signs were replaced between SR 86 / Ajo Way (Exit 99) and Interstate 10 (Exit 101) as part of the Interstate 10/19 Crossing interchange project. Signs installed during the project in 2004 used English units, while other replacements made since and further south retained the metric system. Vocal opposition from area business owners countered efforts from the Arizona Department of Transportation to switch all of I-19 over to English units.2
A $54.3-million in construction upgraded the substandard trumpet interchange joining I-19 with Interstate 10. Commencing in June 2002, “The Crossing” rebuilt the former exchange with new high-speed ramps and added connections to nearby 12th Avenue for I-10 and 29th Street / Silverlake Road for I-19. Work was completed as part the overall reconstruction of I-10 through the Tucson metropolitan area. A dedication ceremony on August 7, 2004 marked the project completion.3
North End – Tucson, AZ
South End – Nogales, AZ
Branch Routes – 0
Mileage – 63.35
Cities – Nogales, Tucson
- Junctions –
Source: December 31, 2018 Interstate Route Log and Finders List
I-19 Annual Average Daily Traffic (AADT)
Initial portions of I-19 ran south from I-10 to Valencia Road (Exit 95) by 1965 and between Mariposa Avenue (Exit 4) and Palo Parado Road (Exit 25) by 1968.
U.S. 89, truncated south of Flagstaff as approved by AASHTO on June 15, 1992, was designated as Business Loop I-10 north of I-19 and as Business Loop I-19 south of I-10. The I-10 business loop was eventually decommissioned by the late 1990s.
North End – Tucson, Arizona
South End – Nogales, Arizona
- “Some I-19 metric signs going,” Tucson Arizona Daily Star, January 19, 2004.
- “Arizona highway signs in metric units may change.” The Arizona Republic, October 5, 2014.
- Building the I-10/I-19 Traffic Interchange,
http://www.1019crossing.comArizona Department of Transportation project web site.
- Southcentral Districts Projects – Interstate 19: Ajo Way Traffic Interchange. Arizona DOT project web site. Page originally accessed on April 21, 2017.
Page updated April 21, 2017.