Northwest NEWS

March 13, 2000


Traffic Talk

by Joe Seet, traffic engineer, City of Woodinville

   Anyone with questions about traffic in Woodinville or the Eastside is welcome to e-mail their inquiries to They will be forwarded to Joe Seet, who is the Senior Traffic Engineer for the City of Woodinville's Public Works Dept. Joe came to the City staff after working for the State of Washington.

   Dear Joe: Sometimes I'm held up in long lines of traffic, which I assume are caused by some accident or something. But when I get up to where the jam started, all the cars have sped back up and I don't see any reason for the jam--no broken down cars or anything. A typical example of this is the rise near the west end of the SR-520 bridge. What's happening?

   Joe: Heavy traffic flow on a congested roadway is very sensitive to any form of disruption. The traffic flow disruption could be very minor, such as a brake light coming on, a slow driver in the fast lane, or even someone changing lanes. The flow disruption could have actually occurred some distance away from where the long lines seem to end.

   These flow disruptions create ripple effects to move back along the traffic flow, just as when a stone causes ripple effects when it hits calm water and the ripples don't dissipate until they get far away from the stone's entry--so the traffic backups and slowdowns that seem to magically disappear into wide-open roads are simply ripples in the traffic flow.