South Puget Sound Interstate 5 - Severe congestion
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Measures of severe congestion on I-5 in the south 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 how to calculate severe congestion (PDF 5.9MB).
Sources: WSDOT Transportation Safety and Systems Analysis Division and WSDOT TRACFLOW (https://tracflow.wsdot.wa.gov/)
Performance highlights
Severe congestion on I-5 in the South Puget Sound area worsened in 2023 compared to 2022, approaching pre-pandemic levels.
Commuters traveling from Tacoma to Olympia on I-5 experienced severe congestion with speeds of 36 mph or less:
- At 5:15 p.m. on 52.0% of weekdays in 2023, up from 43.0% in 2022
In 2022, severe congestion continued to increase compared to 2021. The congestion level got close to the pre-pandemic level, except for the Lacey to Lakewood and Federal Way to Tacoma commutes, which saw decreaseds in severe congestion compared to 2021. For example, at 4:30 p.m. the Federal Way to Tacoma commute were below 36 mph on 85.7% of weekdays in 2022—a decrease from 93.5% in 2021.
In 2021, most of the commute routes saw an increase in severe congestion conditions compared to 2020, which were still lower than the pre-pandemic levels except Tacoma to Olympia commute. Commuters from Tacoma to Olympia on I-5 traveled less often in severely congested conditions (speeds of 36 mph or less) than in 2020. For example, at 4:45 p.m., speeds on this commute were below 36 mph on 26.7% of weekdays in 2021—a decrease from 34.1% in 2020. Olympia to Tacoma showed an increase in severe congestion in 2021. For example, at 3:55 p.m., speeds on this commute were below 36 mph on 14.7% of weekdays in 2021—an increase from 7.4% in 2020.
In 2020, due to the statewide response to COVID-19 there was significant decrease in severe congestion compared to previous years. Commuters from Tacoma to Olympia on I-5 traveled in severely congested conditions (speeds of 36 mph or less) less often than in 2019. For example, at 4:45 p.m. speeds on this commute were below 36 mph on 34.1% of weekdays in 2020—a decrease from 46.4% in 2019.
In 2019, commuters from Tacoma to Olympia on I-5 traveled in severely congested conditions (speeds of 36 mph or less) slightly more than in 2018. For example, at 4:45 p.m. speeds on this commute were below 36 mph on 46.4% of weekdays in 2019—an increase from 44.0% of weekdays in 2018.