Central Puget Sound Interstate 90 - Severe congestion
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Measures of severe congestion on the I-90 corridor in the central Puget Sound region.
Severe congestion
Severe congestion occurs when highway travel speeds are slower than 60% of the posted speed (about 36 mph for a 60 mph speed limit). During this situation, vehicle speeds and spacing decrease along with reduced highway efficiency well below maximum productivity. See WSDOT's Handbook for Corridor Capacity Evaluation (PDF 5.9MB)
Sources: WSDOT Transportation Safety and Systems Analysis Division and WSDOT TRACFLOW (https://tracflow.wsdot.wa.gov/)
Multi-year trends
In 2022, severe congestion in most commute routes continued to increase compared to 2021 due to the ongoing recovery of traffic volume in the wake of COVID-19. However, severe congestion in 2022 was still lower compared to the pre-pandemic level.
In 2020, due to the statewide response to COVID-19 there was a significant decrease in severe congestion compared to previous years.
On the I-90 corridor between Bellevue and Seattle, severe congestion worsened between 2018 and 2019, with larger differences on the Bellevue-to-Seattle commute throughout the day. However, over the same period, severe congestion on I-90 between Seattle and Issaquah mostly improved (with the exception of the morning commute peak on the Issaquah-to-Bellevue commute, which got substantially worse).
Annual highlights
In 2022, severe congestion in commute routes increased compared to 2021 due to the ongoing recovery of traffic volume in the wake of COVID-19. However, severe congestion in 2022 was still lower compared to the pre-pandemic level. Commuters taking I-90 between Bellevue and Seattle drove more often in severely congested conditions (36 mph or less) than in 2021. For example, during the peak morning commute from Bellevue to Seattle, 23.3% of days saw speeds below 36 mph at 8:35 am in 2022 compared to 4.0% in 2021. The peak evening commute was slightly worse in 2022, with 56.6% of days experiencing speeds below 36 mph at 3:40 pm as opposed to 50.8% in 2021.
In 2021, severe congestion in some commute routes increased compared to 2020 due to recover of traffic volume in the wake of COVID-19, but was still lower compared to the pre-pandemic level. Commuters taking I-90 between Bellevue and Seattle drove in severely congested conditions (36 mph or less) saw mixed result in 2021 compare to 2020. For example, during the peak morning commute from Bellevue to Seattle, 1-4% of days saw speeds below 36 mph in 2021 compared 4-14% in 2020. The peak evening commute in 2021, was up with 30-51% of days experiencing speeds below 36 mph as opposed to 12-23% in 2020.
In 2020, due to the statewide response to COVID-19 there was significant decrease in severe congestion compared to the previous year. Commuters driving between Bellevue and Seattle via I-90 drove in severely congested conditions (36 mph or less) less often than in 2019. For example, during the peak morning commute from Bellevue to Seattle, the percent of days with speeds below 36 mph was between 4-14% in 2020 as opposed to being between 63-76% in 2019. The peak evening commute in 2020, with the percent of days with speeds below 36 mph between 12-23% as opposed to between 90-92% in 2019.
In 2019, commuters driving between Bellevue and Seattle via I-90 drove in severely congested conditions (36 mph or less) less often than in 2018. For example, during the peak morning commute from Bellevue to Seattle, the percent of days with speeds below 36 mph was between 63-76% in 2019 as opposed to being between 81-85% in 2018. The peak evening commute was slightly worse in 2019, with the percent of days with speeds below 36 mph between 90-92% as opposed to between 87-89% in 2018.
In 2018, commuters driving between Bellevue to Seattle via I-90 drove in severely congested conditions (36 mph or less) more often than in 2017. For example, during the peak morning commute from Bellevue to Seattle, the percent of days with speeds below 36 mph was between 81-85% in 2018 as opposed to being between 72-77% in 2017. The peak evening commute was same as in 2017, with the percent of days with speeds below 36 mph between 87-89%.