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Aht’Wy Interchange

An interchange will provide safer access to Aht'Wy Plaza residents and local businesses.

Design is complete, with the project set to bid in time to begin construction in spring of 2022. After the structure is built, the Idaho Transportation Department will assume ownership and maintain it as part of the public transportation system.

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Commonly proposed solutions

From adjustments to the speed limit to installing a signal, several options for this area have been considered by the Tribe, the Idaho Transportation Department and other transportation officials. The consensus: an interchange is the best long-term solution.

Read more about commonly proposed solutions, and why the interchange remains the best option.

Aht'Wy Plaza: Interchange Design

The interchange will include a bridge over the highway and four ramps to access the plaza near the east entrance.

The four-lane highway will be separated by concrete barrier, eliminating the existing median, turn lanes and acceleration lanes, to make room for ramps in ITD right of way and avoid environmental impacts. North of the interchange, the grassy median will remain. Retaining walls will be built to support the elevated ramps.

The bridge over US-95 will include a sidewalk and broadband conduit.

The parking area just north of the east entrance will be shifted south to provide the Army Corps of Engineers access to maintain the nearby wetland mitigation site for the Lower Granite Dam (labeled as the goose pasture). The old parking area will be restored with natural vegetation.


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Road Safety Audit

After two drivers died in separate crashes leaving the plaza in late 2018, ITD joined several law enforcement agencies on patrol and facilitated a road safety audit with other transportation experts.

The audit team issued a final report in February 2019 detailing several options to improve safety. The report shows that, based on crash data from 2008 to 2018, 1 percent of crashes statewide results in a fatality. Near the plaza, that rate jumps to 9 percent. The trend continues for other types of crashes resulting in injuries ranging from incapacitating to suspected but not visible.

Final report and ITD response

More crash data

Seven people have died near the plaza since 1997. Between 2012 and 2017, there were 12 crashes at the west entrance and six at the east entrance directly tied to movements to and from the plaza. Most crashes at the entrances have been related to drivers exiting the plaza and failing to yield to oncoming traffic when turning left, prompting the 2017 improvements to the west entrance.

For further analysis of crash data beyond the latest improvements and the road safety audit, ITD’s Office of Highway Safety identified other locations and a road type to compare to based on the volume of traffic, proximity to at least one intersection, the number of lanes and median type. These locations were from all over the state, and data was collected within a mile of the selected location from 2008 to 2017 (with some partial 2018 data).

Of the four locations and road type this intersection data was compared to, it had the greatest rate of crashes per 100 million miles traveled. In fact, the rate was nearly three times greater than these other sites for crashes resulting in fatalities and serious injuries.


Aht'Wy Plaza opens casino with plans to expand
Traffic study conducted to look at how growth would affect drivers
Traffic study identifies need for full interchange upon completion of facility expansion
January 2001
ITD and NPT agree to phased improvements at entrances to handle growth
Fall 2002
Phase one completed with lighting, acceleration lane at east entrance and right turn lanes at both
June 2006
NPTEC passes resolution to pursue interchange instead of the remaining phased improvements
July 2009
NPT hosts public meeting to review alternative designs for interchange
September 2009
Preferred alternative is selected and design continues
NPT works with the Army Corps of Engineer (ACOE) to address concerns over the interchange's design
March 2018
Interchange design adjusted to minimize impacts to ACOE property
Summer 2018
Concrete island constructed at west entrance to restrict left turns from exiting drivers
December 2018
New signs that flash are placed near the entrances, and ITD joins other agencies in emphasis patrol
January 2019
Final design begins, and a road safety audit is conducted
February 2019
Final report from road safety audit delivered
May 2019
Audit improvements made to east entrance
September 2020
Tribe awarded BUILD grant
May 2019

Adjustment made to right turn lane into east entrance

Work will shift the right turn lane into the east entrance to improve line of sight, per the joint audit's recommendation.

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Road safety audit: final report

February 2019

The road safety audit team provided the final report in February which included a range of options that could be constructed in advance of the planned interchange. Both NPT and ITD are moving forward with options for the east entrance, which include adding an acceleration lane for eastbound traffic and widening the westbound right turn lane to create separation between turning and through traffic.

Work on these interim improvements could begin in spring when weather conditions allow for quality paving and once funding is secured.

January 2019

Road safety audit: initial results

ITD hosted a road safety audit to develop other short-term solutions that could be implemented before construction of the interchange. The audit provided NPT several options to pursue with ITD, which will be further detailed in a final report scheduled to come out in February.

Initial results news story


In September 2020, the Nez Perce Tribe was awarded a $19.1-million grant to construct the interchange. Read more.

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