Last night A & N got in trouble for fighting inside the car. A was furios at the punishment we gave him which he felt was unfair. Thinking about it I realized we punish them a lot in the car - relative to the limited amount of time that we spend in the car. I believe this is because the car is a confined space in which I am busy driving and can't take my time to deal with them. When they are fighting in the car I often need to to stop right away. This results in a warning followed by a punishment (when they don't stop their inapropriate behavior).
By contrast, we rarely punish them when we are in a park or even playing a board game in the living room. In those settings they can get away with much more... My advice to them this morning was to be more sensitive to their setting. Parents have much shorter fuses when we are driving a car than when we are playing in a park.