Considering letting a 4 yr child cross the street on their own...

What was actually typed by the author was:

  Nora (4y) can't yet cross streets on her own, but we're starting to practice. 

and that seems like a fine age to start teaching children about road safety.

Five years olds, properly introduced, are able to safely and competently make glass marbles from molten glass they pull from a furnace themselves.