Central Puget Sound Interstate 405 - Severe congestion
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Measures of severe congestion on the I-405 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 continued to increase 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.
Between 2018 and 2019, commutes on I-405 south of Bellevue saw increases in severe congestion, while the commutes north of Bellevue all saw substantial decreases in severe congestion over the same period. The improvements north of Bellevue are likely due to the opening of the I-405 Express Toll Lanes in the fall of 2015 and to the opening of northbound peak use shoulder lane in 2017. For detailed information about the I-405 ETLs, see WSDOT's I-405 Express Toll Lanes Between Bellevue and Lynnwood | WSDOT (wa.gov)
Annual highlights
In 2022, severe congestion increased compared to 2021, due to the ongoing recovery of travel volume in the wake of COVID-19. Commuters driving from Everett to Bellevue on I-405 in 2022 drove in severely congested conditions in the morning (speeds of 36 mph or less) more often than in 2021. For example, at 7:30 a.m. speeds on this commute were below 36 mph on 63.3% of weekdays in 2022—up from 43.3% of weekdays in 2021.
In 2021, severe congestion increased compared to 2020, due to the recovery of travel volume in the wake of COVID-19. Commuters driving from Everett to Bellevue on I-405 in 2021 drove in severely congested conditions in the morning (speeds of 36 mph or less) more often than in 2020. For example, at 7:30 a.m. speeds on this commute were below 36 mph on 43.3% of weekdays in 2021—up from 16.9% of weekdays in 2020.
In 2020, due to the statewide response to COVID-19 there was significant decrease in severe congestion compared to 2019. Commuters in 2020 driving from Everett to Bellevue on I-405 drove in severely congested conditions in the morning time (speeds of 36 mph or less) less often than in 2019. For example, at 8 a.m. speeds on this commute were below 36 mph on 15.8% of weekdays in 2020—down from 84.6% of weekdays in 2019.
In 2019, commuters driving from Everett to Bellevue on I-405 drove in severely congested conditions in the morning time (speeds of 36 mph or less) more often than in 2018. For example, at 8 a.m. speeds on this commute were below 36 mph on 84.6% of weekdays in 2019—up from 79% of weekdays in 2018.
In 2018, commuters driving from Everett to Bellevue on I-405 drove in severely congested conditions in the morning time (speeds of 36 mph or less) were same 2017. For example, at 8 a.m. speeds on this commute were below 36 mph on 78.6% of weekdays in 2018—same as it was in 2017.