Interstate 86 (Western)

Interstate 86 Idaho
History
East End
West End

Overview

The western Interstate 86 is a rural route linking I-east of Twin Falls with I-15 at Pocatello in southeastern Idaho. The freeway parallels the Snake River (Lake Walcott) northeast from Raft River to American Falls. East from there, the route flattens out somewhat adjacent to a Union Pacific Railroad line to the Pocatello vicinity.

There is an eastern Interstate 86, stretching from Erie County, Pennsylvania across the Southern Tier of New York. That route was established in 1999. Prior to that, a second I-86 ran from Hartford, Connecticut to Sturbridge, Massachusetts from 1969 to 1984. Other split routes include I-76, I-84 and I-88.

I-84/86 Salt Lake System Interchange

I-84/86 Salt Lake City Interchange

Construction started in May 2018 reconfigures the 1960-built trumpet interchange joining Interstate 84 and U.S. 30 with the west end of I-86 in Cassia County. The $20 million project realigns the roadways for I-84, eliminating the arc along westbound and shifting the merge with traffic from I-86 to the right. A sweeping loop ramp replaces the shorter radius loop connecting I-86/U.S. 30 west with I-84 east as well. Work wraps up in Summer 2020.2,3

I-86/15 Systems Interchange Complex

Construction anticipated to start in 2022 addresses weaving traffic along Interstate 15 at the east end of I-86 while addressing functionally obsolete bridges within the exchange. A new northbound roadway will be built for Interstate 15 within the existing right of way. The former roadway will be rebuilt as a collector distributor roadway extending north from Pocatello Creek Road. Ramps from I-15 north to I-86 west and I-86 east to I-15 north will tie into the c/d roadway, eliminating the left side ramps within the 1960s-built directional T interchange.

Parallel U.S. Routes

Interstate 86 follows U.S. 30 (former U.S. 30N) throughout its route in Idaho and has one business loop in American Falls.

History

Interstate 15W was initially to be renumbered as part of newly designated I-84 from Pocatello west to the junction with I-80N; Interstate 86 was the number preferred by Idaho and Utah officials for the I-80N corridor. Instead, AASHTO conditionally approved the renumbering of I-15W as I-86 and I-80N as I-84 on July 6, 1977. Approval of the renumbering was finalized by November 1977 and sign changes were to be made by January 1, 1978.1

Route Information

  • East End – Pocatello, ID

  • West End – Declo, ID
  • Branch Routes – 0
  • Mileage – 62.85

  • Cities – American Falls, Pocatello

  • JunctionsI-84 I-15

Source: December 31, 2018 Interstate Route Log and Finders List

I-86 Annual Average Daily Traffic (AADT)

Source: Annual Average Daily Travel Application 2018 AADT – IDT

Southeast Idaho - 1978
Southeastern Idaho – 1978 Idaho Official Highway Map.

Interstate 15W was renumbered as Interstate 86 three years before sign changes were made along I-80N. Both renumberings were approved by AASHTO in 1977.

I-15W button copy sign

Former button copy sign predating the 1980 renumbering of Interstate 15W to I-86 on I-84/U.S. 30 east. Photo taken by Jeff Royston (07/11/07).

I-86 - Southeastern Idaho - 1976

An excerpt from the 1976 Idaho Official Highway Map showing the interchange array along then-Interstate 15W.

Southeast Idaho - 1973

Southeast Idaho – 1973 Idaho Official Highway Map.
Interstate 15E was completed from I-80N east to the Power County line and west from Pocatello to Idaho State Highway 37 (Exit 36) outside American Falls. Completion of the freeway directly over laid the remainder of two-lane U.S. 30 along the Snake River.

Highway Guides

East End I-15 – Pocatello, Idaho

I-86 east at I-15

I-86 east at I-15 - Chubbuck, ID

The first sign for Interstate 15 along I-86 east precedes the diverging diamond interchange (DDI) with U.S. 91 (Yellowstone Highway). Photo taken by Jeff Royston (07/11/07).

I-86 east at US 91/I-15 - Chubbuck, ID

Advancing east from U.S. 91, Exit 63 separates in one mile for Interstate 15 north to Idaho Falls and Butte, Montana and south to Ogden and Salt Lake City, Utah. 07/05/16

I-86 east at I-15 - Pocatello, ID

I-86 spans Hiline Road ahead of the directional T interchange (Exit 63) with Interstate 15. 07/08/16

I-86 east at I-15 - Pocatello, ID

Traffic partitions at the east end of Interstate 86 with two lanes leading south along I-15 through Pocatello. 07/08/16

I-15 north at I-86

I-15 north at I-86 - Pocatello, ID

Interstate 15 meets the east end of I-86 two miles north of Clark Street and Idaho State University. 07/08/16

I-15 north at I-86 - Pocatello, ID

Business Loop I-15 returns to I-15 from Downtown Pocatello via Pocatello Creek Road. The freeway proceeds north another mile to Left Exit 72 for I-86 west. 07/08/16

I-15 north at I-86 - Pocatello, ID

The I-15/86 Systems Interchange project scheduled for 2022-23 will build a new northbound roadway for I-15 and repurpose the old one as a c/d roadway from Pocatello Creek Road to Interstate 86. 07/08/16

I-15 north at I-86 - Pocatello, ID

Left Exit 72 departs I-15 north for I-86 west from Chubbuck to Interstate 84 toward Twin Falls, Boise and Portland, Oregon. 07/08/16

I-15 south at I-86

I-15 south at I-86 - Chubbuck, ID

A diamond interchange was constructed along Interstate 15 with Northgate Parkway, two miles north of I-86. The exchange opened to traffic following a grand opening event held on the morning of December 6, 2019.4 08/09/16

I-15 south at I-86 - Chubbuck, ID

Interstate 15 advances a half mile south from the Northgate Interchange to I-86 west to Chubbuck, American Falls and I-84 to Twin Falls. 08/09/16

I-15 south at I-86 - Chubbuck, ID

Entering the directional T interchange (Exit 72) with I-86 west on I-15 south. The I-15/86 Systems Interchange project in 2022-23 will expand the freeway west to adjacent U.S. 91 along the Chubbuck and Pocatello city line. 08/09/16

I-86 East End Throwback

I-86 east at I-15

I-86 east at US 91 - 2007

One mile west of Interstate 15 at the previous diamond interchange (Exit 61) with U.S. 91 (Yellowstone Highway) to Chubbuck and Pocatello. Photo taken by Jeff Royston (07/11/07).

I-86 east at I-15 - 2006

A diagrammatic overhead assembly replaced these ground level signs for Interstate 15 at the Union Pacific Railroad underpass. Photo taken by Chris Elbert (03/06).

I-86 east at I-15 - 2006

A second lane was added for Exit 63A / I-15 south at the east end of Interstate 86. Blackfoot was removed on the sign replacement for Left Exit 63B. Photo taken by Chris Elbert (03/06).

I-15 north at I-86

I-15 north at I-86 - 2000

One mile south of I-86 on I-15 north at Exit 71 in Pocatello. Photo taken by Kelly G. Kawamoto (08/00).

I-15 north at I-86 - 2006I-15 north at I-86 - 2006

Sign replacements at Exit 72 added Chubbuck for I-86 west. Photos taken by Chris Elbert (03/06).

I-15 south at I-86

I-15 south at I-86 - 2006

Former button copy sign posted two miles ahead of Interstate 86 west (Exit 72). Photo taken by Chris Elbert (03/06).

I-15 south at I-86 - 2006

A half mile north of Exit 72 with I-86 west to American Falls, Twin Falls and Boise. Photo taken by Chris Elbert (03/06).

I-15 south at I-86 - 2006

Southbound Interstate 15 reaches Exit 72 for I-86 west toward Twin Falls. The succeeding exit serves Downtown Pocatello via Business Loop I-15. Photo taken by Chris Elbert (03/06).

Western I-84 – near Declo, Idaho

I-86 US 30 west at I-84

I-86/US 30 west at I-84 - Cassia County, ID

Westbound Interstate 86/U.S. 30 converges with I-84 in a remote area of Cassia County in two miles. 08/09/16

I-86/US 30 west at I-84 - Cassia County, ID

2018-20 construction at the Salt Lake Systems Interchange realigned the loop ramp (Exit 1) for Interstate 84 east to Ogden, Utah to improve its geometry. The gore point for Exit 1 was relocated a third of mile eastward. 08/09/16

I-86/US 30 west at I-84 - Cassia County, ID

Westbound I-84 was realigned in 2019 to eliminate the 1960-built overpass along I-86 west at Exit 1. U.S. 30 combines with I-84 west to Heyburn and Burley. 08/09/16

I-84 US 30 east at I-86

I-84/US 30 east at I-86 - Cassia County, ID

Interstate 84/U.S. 30 proceed east toward I-86 from agricultural areas in the Snake River Valley in rural Cassia County. 08/09/16

I-84/US 30 east at I-86 - Cassia County, ID

Construction underway from May 2018 to Summer 2020 modernized the trumpet interchange with Interstate 86. The exchange was expanded with two lanes for I-84 southeast toward Salt Lake City, Utah and two lanes for I-86/U.S. 30 northeast to American Falls. 08/09/16

I-84/US 30 east at I-86 - Cassia County, ID

Interstate 84 angles southeast to Tremonton, Utah, where it combines with I-15 to Ogden. I-86 parallels the Snake River east to Bannock. 08/09/16

I-84 west at I-86 US 30

I-84 west at I-86/US 30 - Cassia County, ID

The first guide sign for Interstate 86 and U.S. 30 (Exit 222) appears two miles out along I-84 westbound. 07/05/16

I-84 west at I-86/US 30 - Cassia County, ID

I-86/U.S. 30 east overlap to American Falls and the west side of Pocatello. U.S. 30 west joins I-84 to Heyburn. 07/05/16

I-84 west at I-86/US 30 - Cassia County, ID

Construction underway through Summer 2020 rebuilt the Salt Lake Systems Interchange joining I-84/86. Work reconfigured the westbound roadway of I-84 so that traffic from I-86 merges from the right. 07/05/16

I-86 West End Throwback

I-84 west at I-86/US 30 - 2006
I-84 west at I-86/US 30 - 2006

Previous guide signs for Interstate 86/US 30 east on I-84 west. Photos taken by Steve Hanudel (05/17/06).

I-84/US 30 east at I-86 - 2007

Vintage button copy sign on I-84 east for Interstate 86 and the split with U.S. 30. Photo taken by Jeff Royston (07/11/07).

I-84/US 30 east at I-86 - 2007

The Interstate 84 mainline defaulted onto I-86/U.S. 30 east toward American Falls. Photo taken by Jeff Royston (07/11/07).

I-84/US 30 east at I-86 - 2007

I-84 previously made a TOTSO (turn off to stay on) movement at the trumpet interchange with I-86. Photo taken by Jeff Royston (07/11/07).

Sources:

  1. “Interstate 80 to become 84.” The Deseret News, August 13, 1977.
  2. I-84/86: Salt Lake City Interchange. Idaho Transportation Department Projects.
  3. “ITD planning I-84/86 interchange modernization.” KMVT TV-11 (Twin Falls, ID), September 12, 2017.
  4. I-15 Northgate Interchange.” Idaho Transportation Department Projects.

Page updated January 21, 2020.