I-90, ID-41 Interchange

Noise walls were not warranted in the analysis of the interchange, but a study will start in 2021 to look at what it would take—in terms of land and mitigation for adverse environmental effects like noise—to add a third lane to I-90. Noise walls may be included in future expansion of I-90 pending results of the study.

Temporary signals will be installed during construction to handle extra traffic seeking alternative routes. At this time the design team is still determining whether they will be used only during the closure of the westbound off-ramp or if they will be necessary for all of construction.

The design team has consulted with other community partners like emergency services and law enforcement to mitigate any safety concerns with the construction of pedestrian tunnels. The tunnels will be well-lit and short enough to see through to maximize visibility and safety.

Both tunnels will be 14 feet wide and 10 feet tall, which makes them larger than the tunnel under US-95 to access Silverwood. The inside of the tunnel under the I-90 westbound on-ramp will be visible from Seltice Way, and the tunnel under ID-41 will be visible from Primrose Lane, which will help improve safety and ease of patrolling.

The highway will be three lanes wide at this intersection, and by allowing traffic to go straight in all lanes, it maximizes the amount of traffic that can be cleared in one cycle of the signal. Drivers heading south on ID-41 will also need to be in the lane furthest to the right to head west on I-90, and by not designating that lane as a right turn lane only, there will be less weaving as drivers try to get to the freeway.

All of the new ramps will be longer, and the westbound off-ramp will no longer curve. Drivers will have extra time through the use of a parallel lane that extends past the merge point to join traffic. The design team will continue to plan signage that will help drivers determine which lanes will get them where they want to go.

Although the ramp will only be striped for one lane, it will have wide shoulders to keep traffic moving around most crashes as well as to provide room for staging during construction and future maintenance operations. ITD will also use signage to redirect traffic around crashes at that ramp, as it does now by changing messages at signs located near the state line. Another digital emergency sign will be placed on eastbound I-90 near Greensferry with this project.

Existing interchanges in Post Falls are too close together to allow the construction of additional interchanges. Current standards call for interchanges to be spaced at least one mile apart to reduce conflicts between traffic merging onto the freeway and other traffic weaving to exit. As it is, there are no other city routes capable of handling traffic accessing the interstate.

There are no other plans to modify interchanges in Post Falls, but a planning study next year will evaluate whether existing access points need improvements.

Traffic control devices, like signals and stops signs, will stay in place for city intersections based on projected volumes and land use changes. The Ross Point Road and Seltice intersection will transition from a signal to a stop sign since it will no longer serve as the main access point to ID-41 and will become a T-intersection. Traffic will be unable to turn left from Ross Point Road onto Seltice.

Drivers on Third Avenue will have a stop sign to access Ross Point Road, but at Third Avenue and Herborn Place, the stop sign will be for drivers on Herborn Place.

Other changes to traffic control, speed limits and parking may take place after construction by the city.

The new interchange was designed to accommodate future traffic demands and to be compatible with other regional plans.

Future growth was modeled by pulling data from several sources, including: employment rates from the Department of Labor, structure data from Kootenai County, the 2010 national census, planned transportation projects and land use development as projected by cities in Kootenai County. Modeling supports the current design’s compatibility with expansion of ID-41 to three lanes and expansion of I-90 to six lanes. The base model was provided by Kootenai Metropolitan Planning Organization and used by the design team to evaluate how the project will perform with existing and future conditions.

Although not included in this project, ITD is seeking grant funds to relocate the Port of Entry to Huetter to minimize safety concerns posed by commercial traffic heading east through the interchange and up the grade.

Modeling shows that once constructed the new interchange will be safer, more efficient and easier to navigate while being compatible with future expansion of ID-41 and I-90.

Access to businesses on ID-41 north of the interchange will remain the same, though a new median barrier will not allow left turns onto or from the highway. Access will continue to be provided primarily through side streets or signalized intersections to improve traffic flow and make it safer.

Most local roads will continue to function the same as they do now, though access to the freeway south of the interchange will be simplified. Ross Point Road will be restriped to accommodate additional street parking. Other changes to traffic control, speed limits and parking may take place after construction by the city as modifications are not supported by traffic modeling.