South Puget Sound Interstate 5 - Throughput
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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.