Why Might Driving Arouse Anger?
Immobility: When we drive, our bodies remain relatively still, tension builds up when we're physically contricted.
Regulation: Driving is highly restricted whether that be because of the government, or law enforcement officers.
Lack of personal control: Traffic flows not at the pace of you but the rest of the drivers. Impossible to take traffic into your own hands.
Territoriality: Car is a symbol for our individual freedom, when others try to take over our space or "territory," we tend to respond with aggressive actions.
Venting: American culture tends to encourage venting anger. The term "letting it all out" instead of keeping it in is often suggested.
Other theories
Socioenvironmental factors: Evergrowing population, highway engineering that impedes traffic flow, anonymity of driving.
Mental illness factors: Anger disorders that can be triggered by driving.
Cultural habit factors: Stressful world, faulty attitudes, cars act as a mobile form of rudeness and aggression.
by Brandon Veles