The problem that shows up on the road has it's causes both on and off the road. Chief among them, are feelings of frustration, loss of control, and isolation. The roads themselves are one frustration. They have become more crowded. The number of vehicles also has risen.
People are busier, time is at more of a premium.
So road congestion causes even more frustrations. These emotions lead to impaired judgment, saying or doing things they later regret, including engaging in risky behaviors, while attempting to punish or retaliate against the offending driver. Cars offer control, isolation. Cars offer the promise of retaliation without consequence. In a car we feel invincible.