Throwing objects from overpasses or elevated locations at a moving vehicle with the intent to strike is:

• A minor traffic violation with a small fine
• Only illegal if the object damages the vehicle
• Illegal
  Explanation:

  "You may not cause an object to fall from an overpass or other elevated location in the direction of a moving vehicle with the intent to strike it."
• Not punishable as there's no law against throwing objects from overpasses