Interstate 10 in Arizona 2013. The remainder of the old US 80 section was rebuilt to interstate standards, with completion in 2014. East of Tucson, I‑10 parallels and in some cases overlies old US 80 to Benson, and was originally co-signed as US 80 and SR 86. The section of I-10 from Valencia Road to Rita Road was the first construction project in the state of Arizona funded by the Federal Aid Highway Act of 1956. Construction began in 1957 and was completed in 1960. From Benson, the Interstate follows the Southern Pacific mainline east through Willcox and Bowie to New Mexico, rather than
Arizona State Route 143 Interstate 10 and US 60 between the Mini Stack and the Broadway Curve, adding to additional traffic overload and safety issues at the interchange with SR 143/I-10/US 60. The speed limit on I-10 throughout the city of Phoenix is currently . Many other area freeways have limits of , notable exceptions being the Sky Harbor Expressway with , Arizona 51 south of Glendale Rd with 55 mph, and Interstate 17 with . Arizona State Route 143 Arizona State Route 143, also known as SR 143 and the Hohokam Expressway, is a north–south and access-controlled freeway in Maricopa County, Arizona, that