I think the main point is that crazy Mary wasn't crazy at all when it came to cars. She knew one would harm her, even kill her. There is a strong sense of irony all through the song. Eg The kids want to help her by giving her a ride but don't understand why she is so terrified. More irony in the 'no loitering allowed' sign which does nothing to stop the kids congregating under it, drinking, racing cars. All of which culminates in Mary being killed.
I think the main point is that crazy Mary wasn't crazy at all when it came to cars. She knew one would harm her, even kill her. There is a strong sense of irony all through the song. Eg The kids want to help her by giving her a ride but don't understand why she is so terrified. More irony in the 'no loitering allowed' sign which does nothing to stop the kids congregating under it, drinking, racing cars. All of which culminates in Mary being killed.