Central Puget Sound Interstate 5 - Severe congestion
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Measures of severe congestion on the I-5 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 slightly increase compared to 2021 due to the ongoing recovery of traffic volume in the wake of COVID-19. However, severe congestion was still significantly lower than 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.
From 2018 through 2019, the central Puget Sound region experienced substantial economic
growth and increased employment, which resulted in more commuters on the road. Additionally, rapidly
increasing housing prices caused many people to move further from their workplaces to find affordable housing; many of these people commute on I-5.
Annual highlights
In 2022, severe congestion did not change significantly compared to 2021 but it was still significantly lower than the pre-pandemic level. Commuters heading from Seattle to Everett on I-5 in 2022 drove in similar severe congested conditions (speeds of 36 mph or less) compared to 2021. For example, at 4 p.m. speeds on this commute were below 36 mph on 56.2% of weekdays in 2022, slightly down from 59.8% in 2021. During the peak morning commute from Everett to Seattle, 45.6% of days in 2022 had speeds below 36 mph compared to 35.7% in 2021. In 2022, 48.8% of the peak evening commute had speeds below 36 mph compared to 64.6% in 2021.
In 2021, severe congestion increased compared to 2020 due to the recovery of traffic volume in the wake of COVID-19. Commuters heading from Seattle to Everett on I-5 in 2021 drove in severe congested conditions (speeds of 36 mph or less) more often than in 2020. For example, at 4 p.m. speeds on this commute were below 36 mph on 59.8% of weekdays in 2021, compared to 28.4% in 2020. During the peak morning commute from Everett to Seattle, 35.7% days in 2022 had speeds below 36 mph was compared to 35.7% in 2021. In 2021, 64.6% of the peak evening commute had speeds below 36 mph compared to 25.9% in 2020.
In 2020, due to the statewide response to COVID-19 there was a significant decrease in severe congestion compared to previous years. Commuters driving from Seattle to Everett on I-5 drove in severely congested conditions (speeds of 36 mph or less) less often than in 2019. For example, at 4 p.m. speeds on this commute were below 36 mph on 28.4% of weekdays in 2020—down from 84.0% of weekdays in 2019. During the peak morning commute from Everett to Seattle, the percentage of days with speeds below 36 mph was between 17.2% in 2020 as opposed to being between 81.8% in 2019. The peak evening commute in 2020, with the percentage of days with speeds below 36 mph between 25.9% as opposed to between 72.7% in 2019.
In 2019, commuters driving from Seattle to Everett on I-5 drove in severely congested conditions (speeds of 36 mph or less) less often than in 2018. For example, at 4 p.m. speeds on this commute were below 36 mph on 84.0% of weekdays in 2019—down from 88.1% of weekdays in 2018.
In 2018, commuters driving from Seattle to Everett on I-5 drove in severely congested conditions (speeds of 36 mph or less) about the same as in 2017. While, at 4 p.m. speeds on this commute were below 36 mph on 88.1% of weekdays in 2018—up from 84.6% of weekdays in 2017—the majority of the trends for this evening commute are almost identical.