It could also mean that you feel your mother is not handling or dealing with things in the manner that you would. You would have gone right out into the back yard straight away and confronted him. She chooses otherwise, whether for appearances sake or another reason but she still gets there in a roundabout manner. Dreaming of your childhood home or dreams set in your childhood home often deal with past issues or reveal the roots of your present day thoughts and beliefs and how they came about. The writing was on the wall. It was clear that there was emotional abuse, everyone was aware of it, but everyone handled it differently and it was kept to the backyard, out of sight as if it didn't happen. The car is like the elephant in the room. It's there, but not addressed.