An ambulance still waits six seconds. On purpose.

transcript

An ambulance is coming. North and south are green. Make east and west green right now? That's a crash.

End the north-south green now. Yellow runs four seconds. Then all red, two seconds. The junction empties. Then east-west gets a held green. Six seconds after the request.

A jump to green skips the clearance. It creates the crash. Better: pick a different next phase. The clearance is shared.

The green is held until the vehicle is clear. Or sixty seconds at most. A stuck sensor can't hold a road forever. Then yellow, all red, and the cycle carries on.

Anyone still crossing sees flashing don't walk. They have until the end of the all red to finish. Nobody is in the road when the cross traffic starts.

Time is passed in. Nothing sleeps. So the whole scenario runs in a millisecond. And the six seconds is a plain number you can assert.

Override the order. Never the clearance.

Full breakdown in the lecture.