alt Hacker NewsIn California, I would see a single CHP vehicle bring an entire freeway to a standstill, for whatever emergency reason. They would activate lights/sirens and then simply swerve wildly through every lane, while incrementally slowing down. Works a treat. Everybody on the road could tell, it was serious business!
That's called a rolling slowdown or stop. Washington State Patrol does that too, when they haven't got comprehensive traffic management set up yet for a collision/incident.