Central Puget Sound Interstate 5 - Delay
On this page:
Measures of delay on the I-5 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, 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 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 traffic volume in the wake of COVID-19, and some locations of the corridor surpassed pre-pandemic levels. Southbound I-5 between SeaTac and SR 520 experienced significant increases in delay. Travel delay on I-5 occurred in the same sections as previous years, with the most intense vehicle delay occurring northbound between the I-90 interchange and Northgate (including around downtown Seattle) and southbound at the SR 520 interchange and SeaTac.
In 2022, delay slightly increased compared to 2021 due to the ongoing recovery of traffic volume in the wake of COVID-19. However, delay was still significantly lower compared to the pre-pandemic levels. Travel delay on the I-5 corridor occurred in the same sections as previous years, with the most intense vehicle delay occurring northbound between the I-90 interchange and Northgate (including around downtown Seattle) and southbound at the SR 520 interchange and SeaTac.
In 2021 delay increased compared to 2020 due to the ongoing recovery of traffic volume in the wake of COVID-19. However, delay was still significantly lower compared to the pre-pandemic level. Travel delay on the I-5 corridor occurred in the same sections as previous years, with the most intense vehicle delay occurring northbound between the I-90 interchange and Northgate (including around downtown Seattle) and southbound at the SR 520 interchange and SeaTac.
In 2020, due to the statewide response to COVID-19 there was a significant decrease in delay compared to previous year. Travel delay occurred in the same locations as in 2019, but there was considerably less. As in 2019, the most intense vehicle delay on the I-5 corridor occurred northbound between the I-90 interchange and Northgate (including around downtown Seattle), as well as southbound at the SR 520 interchange and SeaTac.
In 2019, vehicle delay on I-5 in the central Puget Sound region occurred in the same locations as in 2018, but there was slightly less of it. As in 2018, the most intense vehicle delay on the I-5 corridor occurred northbound between the I-90 interchange and Northgate (including around downtown Seattle), as well as southbound at the SR 520 interchange and SeaTac. Delay was present on I-5 in the Seattle area in at least one direction for the entire day in 2019, following the same trend from 2018 and 2017. Northbound morning delay was most intense approaching Seattle, while northbound evening delay extended from south of the I-90 interchange to Everett. Delay on the southbound morning commute extended from Everett to just south of the I-90 interchange in Seattle. Southbound delay on I-5 between Northgate and Seattle began at noon in 2019 and continued until 6 p.m., while delay just north of SeaTac lasted from 2-6 p.m., as in previous years.