Why it matters: Since 2008, Seattle-area voters have approved more than $65 billion to grow the region's light rail system.

Originally around 2013, the Ballard Link Extension was envisioned as an at-grade alternative. Transit advocates and others pushed for complete grade separation for faster speed and reliability.

Still, that would leave all of the region's existing passenger rail services in the dust. Amtrak's Cascades line runs on a similar route through Portland, Seattle and Vancouver, BC, but it shares ...