Interstate 184 Idaho

U.S. 20-26 transitions from West Front Street onto a freeway alignment in downtown Boise; the freeway eventually becomes Interstate 184 upon crossing the Boise River west of here. This view looks west at the U.S. 20-26 freeway transition from a centrally-located, 12-story parking garage. The freeway originates from a one-way couplet (West Front Street and West Myrtle Street) that merges together here and forms the freeway. The sign shows "To Interstate 84" and indicates that the freeway carries U.S. 20-26 west. The sign does not include a shield for Interstate 184. Of the five lanes of westbound West Front Street, the left lane is a left turn only lane onto South 13th Street, the middle three lanes transition onto the freeway, and the right lane continues along West Front Street. Photo taken by David Stybr (06/03/06).

Routing

Interstate 184 is the short spur from Interstate 84 serving downtown Boise. It carries as many as eight through lanes along its short distance. It is the only three-digit Interstate Highway in Idaho. Interstate 184 begins at Interstate 84 Exit 49 and extends northeast to culminate at the U.S. 20-26 Chinden Boulevard interchange (Exit 3) near the Boise River crossing. The freeway continues a bit further east as U.S. 20-26 before tranisitioning into the West Myrtle Street (eastbound) and West Front Street (westbound) couplet. This viaduct segment between the Boise River and the couplet is notably different from Interstate 184. Even though it is a freeway, it has a reduced speed limit and an unnumbered exit at West River Street.

History

The Boise connector has appeared in planning maps since the 1960s. It was approved as Interstate 180 by AASHTO on June 30, 1970. Some Idaho Official Maps and Rand McNally maps of Idaho showed Interstate 184 as Interstate 180N in the 1970s, referencing the time when Interstate 84 was designated as Interstate 80N prior to 1980. AASHTO approved the renumbering of Interstate 180 to Interstate 184 on October 13, 1979. After Interstate 84 was commissioned and signed in 1979 and 1980, Interstate 184 in Boise was also briefly signed as Business Loop I-84. This designation was ultimately eliminated to reduce duplicative designations, as the business route was signed along with U.S. 20 and U.S. 26 for a portion of its former length.

The following map shows the original route of Interstate 180N in Boise. This map is an excerpt from the Idaho Official State Map from 1976 (Boise strip map - note the alignments of U.S. 30 and Idaho 55, both of which have changed since 1976):

According to AARoads contributor Kelly G. Kawamoto, the interchange of Interstate 84 and Interstate 184 at the latter's western terminus was reconstructed in the early 2000s to cope with an increasing traffic demand. The Boise metropolitan area, like many cities in the mountain west, have grown substantially and have required road expansions.

Highway Guide

Western Terminus - Interstate 84 and U.S. 30 - Boise, Idaho
Perspective from Interstate 84 and U.S. 30 East
Along eastbound Interstate 84 and U.S. 30, the first indication of the pending left exit split with Interstate 184 is this diagrammatic sign about two miles west of the interchange. Photo taken by AARoads (08/09/16).
The split between Interstate 84 and Interstate 184 is one mile ahead. This interchange has been reconstructed in recent years to accommodate more lanes. Photo taken by AARoads (08/09/16).
Use Interstate 184 east to the first exit to connect to Franklin Road, which is Exit 1 on the new freeway. Photo taken by AARoads (08/09/16).
Eastbound Interstate 84/U.S. 30 will reach Exit 50A-B, Cole Road and Overland Road (right exit) immediately after Exit 49, Junction Interstate 184 east to Franklin Road (left exit). Photo taken by AARoads (08/09/16).
The left three lanes depart for Interstate 184 east to downtown Boise, with a connection to Franklin Road. The middle three lanes continue straight ahead on eastbound Interstate 84, and the right lanes exit to Cole Road and Overland Road. Photo taken by AARoads (08/09/16).
Perspective from Interstate 84 and U.S. 30 West
This is one of the advance warning signs along westbound Interstate 84 and U.S. 30 for Exit 49 (Interstate 184) and Exit 50 (Overland Road) in Boise. Interstate 84 and 184 directional overhead on west Interstate 84. This is a unique interchange because both Overland Road and Cole Road intersect on top of the cut and cover tunnel that crosses the freeway. This reconstructed section of Interstate 84 was completed in 1996 as part of an ongoing project to widen Interstate 84 in the Boise area due to the increasing traffic. A new three lane flyover ramp was opened in May 2000 near where these pics were taken to handle Westbound Interstate 184 to Eastbound Interstate 84 traffic replacing an old one-lane ramp. Photo taken by Steve Hanudel (05/17/06).
Perspective from Interstate 184 East
After transitioning from Interstate 84, this is the first reassurance shield along eastbound Interstate 184. Photo taken by Steve Hanudel (05/17/06).
After transitioning from westbound Interstate 84, this sign bridge indicates that the left lane will connect to eastbound Interstate 184, while the right lane exits to Franklin Road. Photo taken by Steve Hanudel (05/17/06).
Interstate 184 was reconstructed recently, with a median barrier, three through lanes of traffic, high mast lighting, and concrete paving. Photo taken by Steve Hanudel (05/17/06).
Shortly thereafter, this is the second shield along eastbound Interstate 184, with four lanes traveling toward downtown Boise. Photo taken by Steve Hanudel (05/17/06).
The second exit along eastbound Interstate 184 is Exit 3, Fairview Avenue. After this exit ramp, Interstate 184 prepares to enter downtown Boise. Photo taken by Steve Hanudel (05/17/06).
Perspective from Interstate 184 West
Now traveling west on Interstate 184 after the Cole Road interchange, westbound Interstate 184 meets Franklin Road at Exit 1A. The final interchange with Interstate 84 is Exit 0. Photo taken by AARoads (08/31/06).
The left lanes and right lanes transition to Interstate 84/U.S. 30 west to Nampa/Ontario, while the middle lanes connect to Interstate 84/U.S. 30 east to Idaho Falls. Photo taken by AARoads (08/31/06).
Choosing the ramp to eastbound Interstate 84 and U.S. 30 to Twin Falls, this ramp carries three lanes onto eastbound and one lane to westbound. Photo taken by AARoads (08/31/06).
The three-lane ramp joins Interstate 84 and U.S. 30 east at this point. The next exit on mainline Interstate 84 is Exit 50B, Cole Road/East Overland Road. Photo taken by AARoads (08/31/06).
Prior to reconstruction, this photo shows the former directional overhead on Interstate 184 westbound at Curtis Road. Interstate 184 was reconstructed along the entire freeway between 2000 and 2005. As reconstruction of each interchange is complete, the interchange received new signs and exit numbers. Photo taken by Zachary Maillard (10/00).
Eastern Terminus - Downtown Boise, Idaho
Perspective from Interstate 184 East
Interstate 184 west ends at the offramp to Exit 3, Fairview Avenue. Ahead, U.S. 20-26 proceed east over the Boise River toward downtown Boise. A secondary sign for U.S. 20-26 east is posted on the frontage road, which also points to U.S. 20-26 east. Mainline Interstate 184 transitions directly to U.S. 20-26 east, so there's no need to exit here for U.S. 20-26 east. But for those wanting to connect to U.S. 20-26 west along Chinden Boulevard, use Exit 3 and turn left at the traffic signal at the bottom of the offramp. Photo taken by AARoads (08/09/16).
Perspective from U.S. 20-26 Freeway East
Traffic from U.S. 20-26/Chinden Boulevard merges onto the freeway; Interstate 184 ends and is replaced with U.S. 20-26. Ahead, the freeway crosses the Boise River and sees an immediate reduction in speed limit. A mileage sign provides the distance to River Street, 13th Street, and Capitol Boulevard. River Street is served by an offramp, while 13th Street and Capitol Boulevard are at-grade intersections with Myrtle Street. Photo taken by AARoads (08/09/16).
Photo taken by AARoads (08/09/16).
After the Fairview Avenue and Chinden Boulevard interchange, U.S. 20-26 crosses the Boise River on a freeway alignment and meets the offramp to River Street. Turning into downtown Boise, all lanes now have a reduced speed limit of 45 miles per hour, and the pull through lanes indicate U.S. 20-26 solely. After this turn, U.S. 20-26 revert to a surface street (Myrtle Street eastbound and Front Street westbound). Photo taken by AARoads (08/09/16).
Eastbound U.S. 20-26 descends from the viaduct and Boise River bridge to join Myrtle Street eastbound. Ahead is the traffic signal with 13th Street. Photo taken by AARoads (08/09/16).
At the end of the viaduct, U.S. 20-26 meets 13th Street at this traffic signal. This marks the eastern end of the freeway. Photo taken by AARoads (08/09/16).
Perspective from U.S. 20-26 (Front Street) West
Westbound U.S. 20-26/Front Street approaches 13th Street. Freeway guide signs overhead point the way to U.S. 20-26 west to Interstate 184 and Interstate 84 in downtown Boise. Notably, West Front Street continues as a city street and does not carry that name onto the viaduct over the Boise River. Photo taken by AARoads (08/09/16).
U.S. 20-26/Front Street meets 13th Street at this traffic signal. Beyond this point, U.S. 20-26 becomes a freeway leading west over the Boise River. Photo taken by AARoads (08/09/16).
Perspective from U.S. 20-26 West
The freeway immediately ascends onto a viaduct after the 13th Street intersection. Photo taken by AARoads (08/09/16).
The viaduct portion of U.S. 20-26 is not built to Interstate standards as evidenced by the lower speed limit and limited sight distance. Photo taken by AARoads (08/09/16).
Westbound U.S. 20-26 travels along a partial viaduct between 13th Street and the Boise River. Both U.S. routes will depart the freeway at the next exit (Chinden Boulevard, signed as Garden City). A mileage sign provides the distance to the next three exits: Exit 3, Chinden Boulevard (U.S. 20-26 west to Garden City); Exit 2, Curtis Road; and Exit 1A, Franklin Road. Omitted is Exit 1B, Cole Road. Photo taken by AARoads (08/09/16).
Just before crossing the Boise River, the speed limit along westbound U.S. 20-26 increases from 45 miles per hour to 60 miles per hour. The next exit is Exit 3, Chinden Boulevard, which takes U.S. 20-26 west to Garden City. Photo taken by AARoads (08/09/16).
Interstate 184 begins here, at Exit 3, which allows U.S. 20-26 to depart the freeway west along Chinden Boulevard and brings the freeway up to Interstate standards. Interstate 184 will gain more through travel lanes as it proceeds 3.62 miles southwest toward its rendezvous with Interstate 84. Photo taken by AARoads (08/09/16).

Page Updated January 22, 2017.



More Info

Mileage

State Idaho
Mileage 3.62
Cities Boise
Junctions Interstate 84
Source: December 31, 2015 Interstate Route Log and Finders List
I-184 Idaho Annual Average Daily Traffic

County From: To: AADT Composite
Ada Interstate 184 Exit 1/Franklin Road 65,000
Ada Exit 1/Franklin Road Cole Road 58,000
Ada Cole Road Exit 2/Curtis Road 63,900
Ada Exit 2/Curtis Road Fairview Connector 52,000
Ada Fairview Connector Exit 3/Chinden Boulevard 62,000
Source: 2002 Rural Traffic Flow Map (ITD)