When I am in the grocery store I try to drive my cart like I drive a car. I stay on my side of the aisle and if someone is in the main aisle I let them go first and look both ways before crossing.
I don't get the people that think we are in bumper carts and will just run you over to get a box of crackers when hello there are 50 boxes of crackers
PS is there anyway to add directionals to the grocery cart but oh ya this is Mass and people don't believe in them. Gotta love it.