This very question has, at least once in my life, kept me on the straight and narrow. Maybe I just over-think things, but if so, I’m damn lucky that I do. The process my mind actually went through in the split-second after she said, “It might not be safe to drive home tonight” went something like this:
Cheaters always get caught. Always. And if I never got caught, I’d have to tell my wife some day, preferably on my death bed so there wouldn’t be any consequences for me, except that (1) there would be consequences for her and I don’t want that, and (2) I may never get to make a death bed confession, in which case I’d never get to tell her, but someone else probably would because cheaters always get caught, in which case I’d be a complete weasel for having lied to her all those years without ever 'fessing up, and I couldn’t stand to know that, after I died, my wife and sons might find out what a weasel I really was, so it’s best not to do anything weasely.
Okay, it took more than a split second. Passions cooled, the moment passed, the roads were passable after all. Sorry, I have no advice for this situation.