Central Puget Sound Interstate 5 - Severe congestion


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Measures of severe congestion on I-5 in the central Puget Sound region

Severe congestion

Severe congestion occurs when highway travel speeds are slower than 60% of the posted speed (about 36 mph for a 60 mph speed limit) leading to reduced highway efficiency. 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

Commuters traveling from Seattle to Everett on I-5 experienced severe congestion with speeds of 36 mph or less:

  • At 4 p.m. on 77.4% of weekdays in 2023, up from 56.2% in 2022.

Likewise, travelers experienced severe congestion between Everett and Seattle:

  • At 7:30 a.m. on 67.6% of weekdays in 2023, compared to 45.6% in 2022.
  • At 3:35 p.m. on 71.1% of weekdays in 2023, compared to 48.8% in 2022.

In 2022, severe congestion did not change significantly compared to 2021 but it was still significantly lower than the pre-pandemic level. Commuters heading from Seattle to Everett on I-5 in 2022 drove in similar severe congested conditions (speeds of 36 mph or less) compared to 2021. For example, at 4 p.m.:

  • 56.2% of weekdays in 2022 had speeds below 36 mph slightly down from 59.8% in 2021

During the peak morning commute from Everett to Seattle:

  • 45.6% of weekday commutes in 2022 had speeds below 36 mph compared to 35.7% in 2021
  • 48.8% of the peak evening commute in 2022 had speeds below 36 mph compared to 64.6% in 2021

In 2021, severe congestion increased compared to 2020 due to the recovery of traffic volume in the wake of COVID-19. Commuters heading from Seattle to Everett on I-5 in 2021 drove in severe congested conditions (speeds of 36 mph or less) more often than in 2020. For example, at 4 p.m. speeds on this commute were below 36 mph on 59.8% of weekdays in 2021, compared to 28.4% in 2020. During the peak morning commute from Everett to Seattle, 35.7% days in 2022 had speeds below 36 mph was compared to 35.7% in 2021. In 2021, 64.6% of the peak evening commute had speeds below 36 mph compared to 25.9% in 2020.

In 2020, due to the statewide response to COVID-19 there was a significant decrease in severe congestion compared to previous years. Commuters driving from Seattle to Everett on I-5 drove in severely congested conditions (speeds of 36 mph or less) less often than in 2019. For example, at 4 p.m. speeds on this commute were below 36 mph on 28.4% of weekdays in 2020—down from 84.0% of weekdays in 2019. During the peak morning commute from Everett to Seattle, the percentage of days with speeds below 36 mph was between 17.2% in 2020 as opposed to being between 81.8% in 2019. The peak evening commute in 2020, with the percentage of days with speeds below 36 mph between 25.9% as opposed to between 72.7% in 2019.

In 2019, commuters driving from Seattle to Everett on I-5 drove in severely congested conditions (speeds of 36 mph or less) less often than in 2018. For example, at 4 p.m. speeds on this commute were below 36 mph on 84.0% of weekdays in 2019—down from 88.1% of weekdays in 2018.

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