If that's close enough: How is that a problem? Yes, people over here might just pay the fine (which is completely legal for a lot of cases: In all cases where the state doesn't care about the offender's identity).
But if the 5th only means that you're allowed to protect yourself (and yours), isn't it correct to pay? I currently parse your comment as "Wouldn't the people pay up if they are guilty in the first place?".
Not my native language.
The answer could be "X person borrowed my car", which isn't, itself necessarily covered, however the answer could be "I was driving my car at that time", which is definitely covered by the 5th amendment. Since one of the possible truthful responses counts as testimony against yourself, you don't have to answer the question at all, otherwise non-answers could be seen as implicit confessions.