The last section of old US 80 that carried the I‑10 traffic was an underpass beneath the Union Pacific mainline east of Tucson, where the freeway median shrank to a guardrail at Marsh Station Road and the Pantano railroad overpass was too low. This underpass and section of former US 80 was originally constructed between 1952 and 1955 to replace the older more dangerous route over the 1921 Ciénega Bridge. The Marsh Station Road interchange was replaced in 2011, with the railroad mainline rerouted in 2012 and the railroad overpass removed in 2013. The remainder of the old US 80 section was rebuilt to interstate standards, with completion in 2014.