Researchers demonstrated that hackers could permanently activate the car horn, shoot windshield wiper fluid continuously, disable headlights, falsify the speedometer reading, increase radio volume, and turn off auxiliary lights. In testing, none of these attacks could be stopped by a manual override--which might be enough to cause a car accident on a dimly lit road at night. Alternatively, a well-timed burst of full-volume sound with cut lights and a wiper-fluid-obscured windshield could provoke a sudden accident, but that's a lot of effort and leaves a lot to chance. Mucking about with the speedometer can cause problems, though a driver who can roughly keep up with traffic will be able to get by without it. Most likely result of these attacks? A driver would be annoyed, pull over, get out of the car, and have a long weird call with AAA.