The Seattle area took a big step toward better mobility with a deal to put a railroad line through the Eastside under public ownership.
The old freight line is the only unused corridor straight through the booming suburbs, so preventing it from being sold in pieces was step one. Now there needs to be a plan to add transit and a trail, in conjunction with tolling on the existing roads.
Most important, the region needs to encourage future demand for transportation to grow around this corridor. Transit shouldn't simply serve the density that exists now. After all, today's Eastside grew up around structures that were planned in the 1950s.
Don't think the rail route would work as transportation? A project in Bellevue was announced just this week that would locate thousands of residents and workers within walking distance. In Renton the route could be connected to the Sounder trains, light rail and density near Southcenter. In the north, the corridor serves Woodinville and Snohomish -- booming areas where focusing development around transit infrastructure makes more sense than massive new roads.
Consider this report about one way transit could be added sooner rather than later.