South Puget Sound Interstate 5 - Throughput


On this page:

Measures of throughput productivity on I-5 in the south Puget Sound region

Throughput productivity

Throughput productivity measures the efficient use of the existing highway capacity. It can be reported for vehicles or for persons, making it a very adaptive metric. WSDOT uses the maximum throughput standard as a basis for measurement to assess travel delay relative to a highway's most efficient speed of about 85% of posted speed.

Lost throughput productivity is the percentage of a highway's vehicle throughput lost due to congestion when compared to the maximum 5-minute weekday flow rate observed at a particular location of the highway for that calendar year. Refer to WSDOT's Handbook for Corridor Evaluation (PDF 5.9MB). for details on how to calculate throughput productivity.

Sources: WSDOT Transportation Safety and Systems Analysis Division and WSDOT TRACFLOW (https://tracflow.wsdot.wa.gov/)

Performance highlights

In 2023, throughput productivity at most locations in both directions of I-5 improved compared to 2022, likely due to the completion of I-5 construction near the Tacoma dome. After construction was completed, delay in these sections decreased significantly.

Top of page