I remember when my mother finally allowed me to push the shopping cart and I kept running into her when she would stop to pick something up. She told me I had to be three floor squares behind her at all times. Probably seven feet in total, as long as I have a shopping cart I won't run into the person in front of me. If I don't I might not pay attention and run into them. Luckily I'm still wearing a mask so I might be able to get away with it.