Interstate 90 (I-90) in the Spokane area is one of the region’s key commute and economic corridors. As the region’s population continues to grow, traffic volumes are increasing on I-90. Higher traffic volumes, combined with collisions, and reoccurring congestion, have affected the safety and operational performance, leading to slower travel speeds, and less reliable travel times along I-90. The result is less vehicle throughput and decreased operational performance.
In 2017, the evening commute on eastbound I-90 experienced 3.8 miles of congestion lasting for 1 hour 35 minutes. In 2019, eastbound congestion during the evening commute increased by 0.9 miles to 4.7 miles of congestion from the US 195 eastbound on-ramp to the Freya Street eastbound on-ramp, with the duration increasing to 2 hours 5 minutes.
The Washington State Department of Transportation (WSDOT) installed five eastbound ramp meters on I-90 from US 195 to Hamilton Street. This strategy was identified in the I-90 Four Lakes to Idaho State Line Operations Study https://wsdot.wa.gov/planning/studies/i-90-four-lakes-idaho-operational-study to reduce collisions, preserve and maximize the existing I-90 capacity, and improve reliable travel times. The early result of this operational change is demonstrating more consistent speeds closer to the posted speed limit and more consistent travel times on I-90, while reducing crashes. Crash data for the US 195 ramp meter to eastbound I-90 activated in 2019 has a realized 63% reduction in crashes.
Prior to the activation of the eastbound ramp meters, the evening peak commute would begin developing congestion delay around 3:30 p.m. from the Freya Street on-ramp. Due to the short ramp acceleration lane, and number of vehicles accessing and merge onto eastbound I-90, congestion delays would begin to build back towards the Hamilton Street on-ramp. This cascading effect would continue back to the Browne (Division) Street eastbound on-ramp due to the traffic entering at the Hamilton Street on- ramp. Congestion delays would extend until eastbound I-90 developed into 4.7 miles of congested stop and go traffic to US 195.
Ramp closures can also assist with improving performance. The eastbound Freya Street on-ramp has been closed long-term for traffic control purposes for I-90 paving projects each of the previous two years. In 2020, the on ramp was closed from June 21, through September 29, and it was again closed on June 28, 2021. The on-ramp currently remains closed for construction. During the closures WSDOT evaluated the impacts of the rerouted traffic volumes on the local network, particularly at the Havana Street and 4th Avenue intersection and the Custer Street on-ramp, as that is where the majority of rerouted volume accessed I-90.
To further reduce collisions and improve travel time on I-90, WSDOT is proposing a permanent closure of the eastbound Freya Street on-ramp to I-90. The eastbound I-90 ramp meters from US 195 to Hamilton Street have helped to reduce congestion and improve reliable travel times. However, the eastbound Freya Street on-ramp to I-90 is the location that create the initial congestion bottleneck to form due to the number of vehicles merging and the short acceleration lane. The proposed project will close the existing eastbound Freya Street on-ramp to I-90 and reroute traffic to the eastbound Custer Street on-ramp onto I-90, where an approximate 2500’ acceleration lane currently exists.
Supporting operational analysis for permanent closure
Mainline I-90 operations improve with the closing of the Freya Street eastbound on-ramp, while the Havana Street and 4th Avenue all-way-stop-control (AWSC) intersection operations decrease. Analysis was performed using volume counts from 2018 and 2021 with the Freya Street on-ramp open, and from 2021 volume counts at the intersection of Havana Street and 4th Avenue while the Freya Street on-ramp was closed, and traffic volumes routed to the Custer Street on-ramp. Higher volumes from the 2018 counts were used to demonstrate a worst-case scenario for analysis purposes. Analysis results indicate:
- The eastbound I-90 safety performance modeling predicts for the freeway segment starting just before the Freya Street on-ramp to just past the Custer on-ramp that the crashes will decrease by 2 crashes per year. These crashes are typically high-speed crashes. The analysis further indicates that 1.7 crashes per year out of the total 2 crash per year reduction occur at the Freya on-ramp.
- Using the assumption that all the eastbound Freya on-ramp traffic diverts using 3rd Avenue to use the Custer on-ramp, versus using alternate routes, safety performance modeling predicts the annual crashes at Havana and 4thAve will increase from 1.13 to 2.36 crashes per year. The 3rd Avenue segment from Rebecca Street to the Custer on-ramp will increase from 1.55 to 4.50 crashes per year. Crashes on the 3rd Avenue segment typically occur at low speed.
- The proposed Freya on-ramp closure removes the last bottleneck that starts the evening commute congestion and provides for a more stable and higher speed profile. The I-90 eastbound average hourly spot speeds (4:00-6:00 PM; Tue, Wed, and Thu) before and after the current construction closure, have risen from 39 mph to 59 mph. Speeds just before and after the Custer on-ramp with the added traffic volumes are predicted to remain the same as existing speeds without the Freya on-ramp closure at approximately the speed limit.
- Travel to the Custer Street on-ramp via 3rd Avenue through the Havana Street and 4th Avenue intersection, will increase a drivers travel time from one minute to approximately 2 minutes.
- Closing the eastbound Freya Street on-ramp, I-90 drivers will experience less of a need to make lane change adjustments, reduced weaving, and less need to adjust speeds for on-ramp traffic.
Alternatives to the proposed closure are much higher in costs and include widening I-90 for added acceleration lane and merge, or ramp metering the on-ramp. Improvements necessary to meter the Freya eastbound on-ramp in the period prior to construction of the North Spokane Corridor Interchange are not a preferable public expense when compared to the benefits of closing the ramp. Future construction of the North Spokane Corridor will incorporate additional performance enhancement to access, and address the change in performance along the arterial segment and at the intersection of Havana Street and 4th Avenue. The configuration of the NSC/I-90 interchange is still being determined.
For more detail information, please view our draft study (PDF 3.8MB)