My 4 year old girl has no awareness of danger

Q. My four-year-old daughter has no sense of danger. I can deal with it myself, but I don’t feel comfortable leaving her with other adults in case something happens to her. I am going back to work in September, which is around the time that my daughter starts school. I don’t know how I will bring myself to have someone else collecting her each day. She recently tried to get into a pink car we saw waiting at traffic lights. My husband and I are used to it and have learned to deal with it, but I am not sure how I can warn another adult.