Overview
Construction on the I-84, Karcher Interchange is underway. The project will increase safety and mobility at the interchange and along Karcher Road (SH-55) in Nampa.
Construction is expected to finish in fall of 2025.
What to expect
ITD is making efforts to minimize impacts to the traveling public during construction. Here’s what to expect during construction:
- All lanes will be open during the daytime.
- Major work will take place at night from 10 p.m. to 5 a.m. with one lane open in each direction on Karcher Road (SH-55).
- Overnight closures on I-84 for traffic shifts, bridge work and girder placement.
- Bike lanes and sidewalks in the project area will be detoured.
- Access to businesses will remain open.
- Speed limits will be reduced.
I-84 monthly update: April 2025
Improvements include:
- Re-configuring westbound and eastbound off-ramps to improve safety and traffic flow, and increase capacity.
- Widening the interchange bridge to provide a dedicated lane for the westbound off-ramp traffic to travel westbound on Karcher Road (SH-55).
- Adjusting signals at ramp intersections, Caldwell Blvd and Cassia St.
- Adding a 3rd westbound lane and dedicated right turn lane at the intersection of Karcher Road (SH-55) and Caldwell Boulevard.
- Widening some sidewalks within project limits.
- Repaving Karcher Road (SH-55) from the westbound on-ramps to Middleton Road.
The traffic separator on Karcher Road near Sundance Road will be extended to Cassia Street to address safety concerns with widening Karcher Road. Left hand turns along this stretch of Karcher will be restricted. View a detailed map of the design plans.
Safety benefits
Improving the Karcher Interchange will eliminate queuing on the westbound off-ramp, allow for better flow of traffic on SH-55, and reduce sideswipe crashes by allowing longer merging distances. With an additional westbound lane on SH-55, drivers wouldn’t need to make last-minute, unpredictable lane changes to jockey for better positioning.
Sidewalks improvements are being incorporated to better align with Nampa’s Master Bike and Pedestrian Plan. Buffer zones will separate bikes and pedestrians from the street. Cyclists and pedestrians can expect greater visibility with the addition of a pedestrian flashing beacon at the eastbound on-ramp. Drivers will be able to see an advanced pedestrian flashing beacon to allow for a better response time in slowing down for crossing pedestrians.
Funding
This design is being funded with Transportation Expansion and Congestion Mitigation (TECM) funds as part of Governor Little’s Leading Idaho initiative. The program allows ITD to accelerate project timelines to address rapid growth and build critical infrastructure today that would otherwise take many years to fund and build.
The I-84 corridor is one of 13 approved TECM corridors in the state. Funding for the construction phases on this corridor will be determined based on project readiness and funding availability.
Preliminary estimates value the improvements needed in this corridor at $20 million to $25 million, which includes design, right of way and construction costs. Work will be completed in one season once funding is secured.
Background
Due to significant growth and development, daily traffic counts on the Karcher Interchange have nearly doubled since it was opened in 2006. The growth in this area has outpaced the projections used during design, and increasing capacity is needed to improve safety and traffic flow.
Other projects have provided short-term capacity solutions on the interchange, but further improvements are necessary. View a fact sheet about growth at the Karcher Interchange to learn more about the history of the interchange and how it has been impacted by growth in Nampa.
Timeline
The project began in 2021 and is expected to finish construction in late 2025.
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Winter 2021/Spring 2022
Field work and design process begins
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Summer 2022
Gather public input
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Fall 2022
Design plans finalized
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Winter 2022
Purchase right of way
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Early spring 2023
Prepare construction plans
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Early 2024
Construction begins
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Late 2025
Expected completion
Frequently Asked Questions
Construction is scheduled to start in early 2024 and last for two years. Completion is expected in the fall of 2025.
Current interchange traffic volumes, or “ADTs” (Average Daily Trips), are estimated at 47,959 vehicles per day. It is expected that this number will reach 69,417 by 2045.
Yes, the Karcher Interchange westbound off-ramp free running right entering into a dedicated lane across the interchange, and signal improvements are expected to reduce the traffic stacking that occurs on I-84. The new lane will give traffic additional space, while the signal improvements and free-running right will improve traffic flow onto State Highway 55.
Yes, a new pedestrian flashing beacon will be installed at the Karcher Interchange eastbound on-ramp. Sidewalks on the north side of State Highway 55 between Middleton Road and Caldwell Blvd will be widened, as well as the sidewalks on the south side of SH-55 between Caldwell Blvd and the westbound Karcher Interchange on-ramp.
Yes, an open house took place summer of 2022. It was an opportunity to learn more about the project and the preliminary designs, and also provided feedback to ITD. Public participation and input are crucial to the design process. Feedback given at the public meeting may influence the final design and help decide how traffic is managed during construction.
The decision to widen westbound ramps and southbound lanes was based on the I-84 Traffic Analysis conducted in 2018. The goal was to eliminate queuing on mainline I-84 due to insufficient storage and to optimize signal operations on Karcher Road.
The new westbound lane on Karcher Road is designed to provide traffic coming off the I-84 westbound interstate ramp a dedicated lane to head towards Caldwell Boulevard. The third westbound lane will taper back into two thru lanes beyond the curve to provide for a safe merge into the through lane.
Growth and development in Nampa has outpaced projections, and it is necessary to increase capacity and improve safety at the I-84 Karcher Interchange.
This toolkit from the Idaho Transportation Department includes tips and resources to help customers, vendors and employees thrive during I-84 construction in Canyon County.
Tips for business leaders during construction
- Share information early and often. When you receive detour maps or other information from ITD, share this with your employees, customers and vendors. Social media posts and emails can both be helpful. Sample email and social media graphics for the Karcher Interchange on Instagram and Facebook, as well as I-84 from Centennial Way to Franklin Road for Instagram and Facebook, are included in this kit.
- Sign up for text alerts from Idaho Transportation Department. Text 84CORRIDOR to 1-866-483-8422.
- Identify key contacts at your business for ITD to send email updates. These emails are sent once or twice a month with details about what’s ahead in the next several weeks. Email these names to Kate Wallace at 84corridor@itd.idaho.gov.
- Reach out to the I-84 corridor team. The team can answer questions about construction and help you communicate with customers, employees and vendors. Call (208) 334-8002 or email 84corridor@itd.idaho.gov.
- Stay positive. Customers do notice!
- If access to your business will change during construction, provide advance notice. Consider including this information on your company’s voicemail message, website and social media platforms.
- Remember that the way you talk about construction will influence your customers and employees. For example, giving clear directions to your location helps customers continue to support your business. Saying that “customers can’t get to my business” can discourage some potential customers from trying.
Contact the project team
Email 84corridor@itd.idaho.gov. Call (208) 334-8002 with any questions or to schedule a meeting. Text 84CORRIDOR to 1-866-483-8422 for updates.
Resources
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