Vehicle travel on Washington's state roads fell again last year. It was a modest decline---just 0.8 percent---but as the chart to the right shows, it was a continuation of a full decade of essentially flat traffic. In fact, WSDOT estimates that total traffic on state roads was slightly lower in 2012 than it was in 2002.
There's really not much to say about the trends that I haven't said before. The flat-lining of traffic is due not to one single factor, but to many.