Central Puget Sound Interstate 90 - Delay
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Measures of delay on the I-90 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 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 eastbound graph below is read from left to right, while the corresponding westbound graph is read from right to left. 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 compared to 2021, due to the ongoing recovery of traffic volume in the wake of COVID-19. However, delay in 2022 was still significantly lower than the pre-pandemic level.
In 2020, due to the statewide response to COVID-19 there was no delay on the I-90 corridor 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 commute on I-90.
Eastbound delay on I-90 in the central Puget Sound region was nearly identical in 2018 and 2019 except for an increase in delay at Bellevue. In contrast, westbound delay on I-90 between the I-405 interchange and Seattle decreased over the same period, likely due to the June 2017 opening of the HOV lanes between Bellevue and Seattle.
Traffic on this corridor is heavily influenced by congestion on the major north/south routes: I-5 and I-405. If these routes are congested, traffic backs up onto I-90, resulting in delays.
Annual highlights
In 2022 westbound delay increased compared to 2021 due to the ongoing recovery of traffic volume in the wake of COVID-19. However, delay in 2022 was still significantly lower than the pre-pandemic level. Eastbound vehicle delay on I-90 in this region was nearly the same as in 2021, showing almost no delay in traffic.
In 2021 westbound delay increased compared to 2020, due to the recovery of traffic volume in the wake of COVID-19, but delay in 2021 was still significantly lower than the pre-pandemic level. Eastbound vehicle delay on I-90 in this region was nearly the same as in 2020, showing almost no delay in traffic.
In 2020, due to the statewide response to COVID-19 there was no delay on the I-90 corridor compared to previous year. Traffic volume was significantly lower due to commuter switched to Telework and low bussiness activity in the downtown area. Eastbound vehicle delay on I-90 in the region was sgnificantly lower compare to 2019.
In 2019, eastbound vehicle delay on I-90 in the central Puget Sound region was nearly the same as in 2018, occurring during both the morning and evening commutes in the approach to the I-405 interchange. Westbound delay in 2019 was also similar to westbound delay in 2018, but there was less of it between Bellevue and Seattle, and more in the area around the I-405 interchange; there was delay at both of these locations during the morning and evening commutes.
In 2018, vehicle delay on I-90 was very similar to 2017, except for an increase in westbound delay between Bellevue and Seattle. As in 2017, eastbound delay during both the morning and evening commutes occurred mostly approaching the I-405 interchange. Westbound delay occurred between Bellevue and Seattle as well as approaching the I-405 interchange during both morning and evening commutes, and to a lesser extent between Issaquah and West Lake Sammamish Parkway during the morning commute.