On my way to a family gathering the other day, I witnessed some serious road rage. For a psychology class in school, I remember developing a survey about road rage, and did some reading on the concept in preparation. I read somewhere (and can't find that source now, unfortunately) that there are some people who respond with aggression to many situations, and others who only respond with aggression when they're driving; that is, they are generally friendly, calm people who get supremely pissed off at other drivers.
I can understand this reaction, because I also used to be really bad about road rage. Not the over-the-top, picking fights with other drivers rage; more shouting and flipping people off rage. Either one isn't particularly healthy, and I made a decision a couple of years ago to give up road rage completely. I decided that road rage is like an adult temper tantrum, and it doesn't actually help the situation. In fact, it's more likely to make things worse.
There are a variety of psychological explanations for road rage. A common one stems from the frustration-aggression hypothesis: when something frustrates you, you respond with aggression, especially when you have no control over the situation and can't really do anything to change it. Being stuck behind a bad driver, particularly when you're in a hurry, is incredibly frustrating.
A study by Lupton (read it here) examined people's views on driving and experiences with road rage, and found that driving was viewed as a pleasurable experience that allowed people to feel independent. When they experience frustrations that keep them from feeling that pleasure, and reminding them that they can't control other drivers, it's understandable that they would react with aggression.
However, attributions are also at play. I recently blogged about the fundamental attribution error, which occurs when you apply situational explanations for your own bad behavior, and dispositional explanations for other's bad behavior. In the case of driving, if I'm driving like a jerk, it's because I'm in a hurry; if someone else is driving like a jerk, well, it's because they're a jerk. And jerks make us angry.
Whether you realize it or not, when you get mad at other drivers, it might be because you're assuming their poor driving is dispositional, rather than situational. It's a lot harder to get mad at other drivers if you assume that they too are in a hurry or have somewhere else they need to be. It might be incorrect - maybe that bad driver is just a jerk. But if it helps keep you from getting upset, who cares?
I was talking to my husband about this, and he commented that, when you're in the moment (with road rage), it's hard to let it go, especially when the other driver starts to road rage. I told him that in that moment, you make a choice: you can choose to escalate or de-escalate. When another driver rages, I choose to let it go. Sure, he may laugh at me, and think I'm an idiot. But who cares what that guy thinks?