Part of that is easy - if you can drive no farther, try to drive back, the shoulders are now valid lines of retreat.
If you can’t do that, get out of the car and RUN LIKE HELL.
“RUN LIKE HELL.”
I know! But... I know I’ve been in serious situations and have not always responded to them as a worst-case situation (”this really can’t happen....”) Luckily they didn’t become as “worst case” as they could have been. Hope this doesn’t either (hope the bridge stays up long enough for folks to get out).