I saw a video of guys in a salt truck jumping out just before it slid into the lake in Chicago. The time between the slide starting and them jumping out of the truck leads me to think that they immediately moved to jump at the start of the slide, with no hesitation about whether it was going into the lake.
So, had they already determined that any slide meant that the truck was going in the lake? Was this based on previous experience? (Also, probably not wearing seatbelts, and really prepared to jump?)