Central Puget Sound Interstate 405 - Delay
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Measures of delay on I-405 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, refer to WSDOT's
Handbook for Corridor Capacity Evaluation (PDF 5.9MB).
Heat maps
The heat maps below show 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 bottom to top, while the corresponding southbound graph is read from top to bottom. For additional details on how to read heat maps, refer to 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/)
Performance highlights
In 2023, delay increased compared to 2022 due to the ongoing recovery of travel volumes in the wake of COVID-19. Amounts of delay became almost same or some location of the corridor surpassed the delay compared to the pre-pandemic. Northbound between SR 167 and Newport experienced significant increase in delay. The worst vehicle delay on I-405 occurred southbound approaching the I-90 interchange during the evening commute.
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.