Central Puget Sound Interstate 405 - Delay
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Measures of delay on the I-405 corridor in the central Puget Sound region.
Travel delay
Travel delay is the amount of extra time spent at speeds below a given threshold—such as the posted speed limit or the maximum throughput speed on a highway. WSDOT uses maximum throughput speed (85% of posted speed limit) as its threshold for calculating delay, which it measures in either annual hours of delay per vehicle or annual hours of delay per person. For details on methodology to calculate travel delay, see WSDOT's
Handbook for Corridor Capacity Evaluation (PDF 5.9MB).
Heat maps
The heat maps below shows vehicle hours of delay by time of day (measured in 5-minute intervals) and milepost. The darker the shading in a particular spot on the heat map, the more hours of delay occurred at that time and place. Shading is standardized across all the corridors to allow for comparison.
There is a separate heat map for each direction of travel. The northbound graph below is read from the bottom to the top, while the corresponding southbound graph is read from the top to the bottom. For additional details on how to read heat maps, 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, delay continued to increase due to the ongoing recovery of traffic volume in the wake of COVID-19. However, the delay 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 delay 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 in search of affordable housing; many of these people commute on I-405.
Highway capacity constraints vary based on the presence of managed lanes and multimodal travel options; the I-405 corridor is served by transit buses, HOV lanes and, between Bellevue and Lynnwood, by Express Toll Lanes (ETLs). 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 delay increased compared to 2021 due to the ongoing recovery of travel volumes in the wake of COVID-19. However, the delay in 2022 was still lower compared to the pre-pandemic level. Vehicle delay in 2022 on I-405 was more than it was in 2021. The worst vehicle delay on the I-405 corridor occurred southbound approaching the I-90 interchange during the afternoon.
In 2021 delay increased compared to 2020 due to the recovery of travel volumes in the wake of COVID-19. However, the delay in 2021 was still significantly lower than the pre-pandemic level. Vehicle delay in 2021 on I-405 was more than it was in 2020. The worst vehicle delay on the I-405 corridor occurred southbound approaching the I-90 interchange during the afternoon.
In 2020, due to the statewide response to COVID-19 there was significant decrease in delay compared to the previous year. Vehicle delay in 2020 on I-405 was substantially less than in 2019. The worst vehicle delay on the I-405 corridor occurred southbound approaching the I-90 interchange during the afternoon.
In 2019, vehicle delay on I-405 was very similar to both 2017 and 2018. As in previous years, the worst vehicle delay on the I-405 corridor occurred southbound approaching the I-90 interchange during the afternoon, and northbound in the Renton area during the morning commute.
In 2018, vehicle delay on I-405 was very similar to 2017, with small increases in the amount of northbound delay north of SR 520. As in 2017, the worst vehicle delay on the I-405 corridor occurred southbound approaching the I-90 interchange during the afternoon, and northbound in the Renton area during the morning commute.