Well, I had my first emergency stop today.
Heading toward a traffic light, the light was green, I was about 125 feet from the crosswalk, at 38 mph (2 miles per hour under the speed limit).
The light turned yellow, then almost immediately turned red. This intersection has a traffic camera on it, and it's a notorious intersection... they decreased the time that the yellow light shows so that it forces people to choose between 'running the red', or slamming on their brakes; as a way of getting more 'you ran a red light' traffic ticket income. Unfortunately, it also causes a lot of rear-ender traffic accidents.
I quickly glanced in my rear view mirrors to be sure I had room in front of the car behind me as I cranked down on the brakes, the rear wheel locked a bit so I let off it until I could just hear it barely squealing a little bit near its traction limit.
I stopped about 3 feet inside the crosswalk, then backed up.
Now, at 38 mph, this all took a total of about 2 seconds. A car wouldn't have been able to stop, and would have gotten a ticket (or gotten rear-ended if they'd tried to stop).
Somebody should tell the DMV that their policy of ultra-short yellows as an income generator is dangerous, which is diametrically opposed to the purpose of traffic cameras in the first place.