These figures roughly comport with Washington Post surveys on driver rage. Between 2010 to 2013, the percentage of D.C.-area drivers who say they often felt "uncontrollable anger toward another driver on the road" doubled, from 6 percent to 12 percent. Commuters are more likely to experience blinding rage than non-commuters (no surprise there), the young are more angry than the old (ditto), and politically speaking Democrats are the political group least likely to drive angry, while independents are the most.
A 2013 study by Christine Wickens of the Centre for Addiction and Mental Health in Toronto offers some insight into what gets our blood boiling on the road. Wickens analyzed 5,624 complaints posted to the website roadragers.com, which is an online forum where people can go to blow off steam about bad drivers. The thing that ticks drivers off most? Weaving between lanes and cutting people off. Speeding, general hostility and tailgating are also common complaints.
The Nevada incident illustrates how quickly little acts of aggression can spiral out of control. The shooting victim, Tammy Meyers, honked at a driver who "sped up behind her," according to the NBC News report. The drivers got out and had a verbal altercation, and then Meyers left, picked up her son, who was armed, and went looking for the other driver. After an unsuccessful search she returned home where the driver was waiting for her, and shot her.