Monday's gridlock on Interstate 5, caused by a rolled-over tanker carrying propane, had an impact that could be felt across the nation.
At home, people were stuck in traffic for hours.
But for Seattle firefighters who made the call to shut down both directions of I-5. the decision was all about potential catastrophic results.
"For us, unfortunately, we have to evacuate a very large area thinking about the worst case scenario.," said Lt. Ryan Nash of the Seattle Fire Department.
When it comes to propane, Nash says firefighters prepare for a disaster. In this case, that was a boiling liquid expanding vapor explosion, or what firefighters call a "BLEVE."