four-lane bypass of American Falls, began in May 1958 and was completed in October 1959. The westernmost stretch of the highway near Raft River was opened in 1963 as part of work on I-80N east of Heyburn. The Chubbuck section of the freeway was opened to traffic in July 1968 and was followed three months later by an extension to Pocatello Air Terminal west of the city. I-15W between American Falls and the airport was opened to traffic in September 1972. US-30N was superseded by US-30 in 1972. In 1973, the American Association of State Highway and Transportation Officials (AASHTO) adopted a new preference for duplicate numbers in lieu of suffixed designations. As a result, I-15W was redesignated as I-86 in 1978; it was originally submitted as part of I-84 (the successor to I-80N). By 1980, most of the freeway was completed, except for a section between Raft River and American Falls that was graded and scheduled to be temporarily paved. The final four-lane section was constructed at a cost of $33 million (equivalent to $ in ) beginning in 1978 and was dedicated on October 11, 1985. The highway's construction was delayed by careful rock blasting next to utility lines, historic sites, and native wildlife habitats. The interchange with US-91 in Chubbuck was later rebuilt in 2013 as the state's first diverging diamond interchange, which helped reduce the rate of collisions at the interchange. ITD plans to rebuild the interchanges at the western and eastern termini of I-86 to meet modern standards and improve safety. Reconstruction of the western interchange at I-84 near Declo began in May 2018 and was completed in late 2020, replacing the trumpet configuration with a modified Y. A major rebuild of the eastern interchange at I-15 in Chubbuck began in August 2022 and is scheduled to be completed in 2025 at a cost of $112 million. The new design eliminates left-side ramps from I-15 and allows traffic from the Pocatello Creek Road interchange to merge onto either freeway. Exit list Business route Interstate 86 Business (I-86 Bus) is an business route of I-86 that runs between two interchanges in American Falls. It travels northeast from the SH-37 interchange into downtown American Falls on Lincoln Street and Fort Hall Avenue, following the former route of US-30N. The route turns west onto Idaho Street for two blocks and crosses over a railroad before beginning its concurrency