How accurate are WSDOTs calculated travel times?
The accuracy of calculated travel times varies depending on congestion. The equipment used to estimate speeds on the freeway becomes inaccurate when traffic exceeds 60 mph or drops into stop-and-go congestion. Unfortunately, many of the major commutes in the Puget Sound area involve sections of freeway where speeds don’t fit within this range. WSDOT verified the accuracy of the estimates by having UW students drive the route and record the time as they passed checkpoints along the way. These tests showed that the estimated travel time was accurate (within five minutes) during 84 percent of our tests.
