People tend to act more selfishly in cars than they do outside of them, much like many people do with the relative anonymity of the internet. I suspect it is be

People tend to act more selfishly in cars than they do outside of them, much like many people do with the relative anonymity of the internet. I suspect it is because drivers are in semi-protected pockets of their own space, and they're essentially sitting still - there is not much they can do to discharge physical frustration caused by traffic besides yelling, giving people the finger, or driving more aggressively.