If you park downhill on a road with a curb, turn your front wheels

Explanation

If you park downhill with or without a curb, turn your front wheels to the right. If you park uphill with a curb, turn your front wheels away from the curb. If you park uphill without a curb, turn your front wheels toward the edge of the road. In this way, if your car starts to roll downhill, either the curb will block it or it will roll away from traffic.