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 eastbound graph below reads from left to right, while the corresponding westbound graph reads from right to left. For additional details on how to read heat maps, refer to the Handbook for Corridor Capacity Evaluation (PDF 5.9MB).
Vehicle delay on northbound I-5 in the south Puget Sound in 2023 increased by 39% compared to 2022, while the southbound delay decreased by 34% compared to 2022. Vehicle delay on the northbound corridor shifted locations from milepost 134 to milepost 131. WSDOT is monitoring this area to gauge if operational changes are needed (i.e. ramp metering).
In 2022 vehicle delay decreased by 27% compared to 2021. Vehicle delay on I-5 in the south Puget Sound region occurred in the same locations as in 2021. The most intense vehicle delay on the I-5 corridor occurred between southbound Federal Way and around Fife. The northbound delay from 5 a.m. to 6 p.m. in 2022 was less than the southbound delay between 1 p.m. and 8 p.m. The northbound delay decreased by roughly 76% compared to 2021, while the southbound delay decreased by roughly 10% compared to 2021.
In 2021 delay increased compared to 2020 but still significantly lower compared to pre-pandemic levels. Vehicle delay on I-5 in the south Puget Sound region occurred in the same locations as in 2020. The most intense vehicle delay on the I-5 corridor occurred between Lakewood and around the Tacoma dome. The delay northbound from 5 a.m. to 6 p.m. in 2021 was less than the southbound delay between 1 p.m. and 8 p.m.: the delay northbound increased by roughly 156% compared to 2020, while the delay southbound decreased by roughly 129% compared to 2020.
In 2020, due to the statewide response to COVID-19 there was a significant decrease in delay compared to previous year. Vehicle delay on I-5 in the south Puget Sound region occurred in the same locations as in 2019, but less of it. As in 2019, the most intense vehicle delay on the I-5 corridor occurred between the Tacoma Dome and Federal Way. The delay northbound from 5 a.m. to 7 p.m. in 2020 was less than it was in southbound delay between 2 p.m. and 8 p.m.: the delay northbound decreased by roughly 79% compared to 2019, while the delay southbound decreased by roughly 72% compared to 2019.
In 2019, vehicle delay on I-5 in the south Puget Sound region occurred in the same locations as in 2018, but there was slightly more of it. As in 2018, the most intense vehicle delay on the I-5 corridor occurred between the Tacoma Dome and Federal Way. The delay northbound from 5 a.m. to 7 p.m. in 2019 was more severe than it was southbound delay between 2 p.m. and 8 p.m.: the delay northbound increased by roughly 38% compared to 2018, while the delay southbound in the morning increased by roughly 20% compared to 2018.
