One problem with self-driving cars is people.
The Los Angeles Times reports that of six crash reports filed in California so far this year, two involved a person attacking a robot car.
Both incidents happened in San Francisco, according to Department of Motor Vehicles records.
On Jan. 2, a vehicle operated by General Motors' Cruise driverless car division was waiting at a green light for pedestrians to cross when a shouting man ran across the street against the do-not-walk signal and struck its bumper and hatch, damaging a taillight.
The car was in autonomous mode but a driver was behind the wheel.
On Jan. 28, another GM autonomous vehicle with a human driving had stopped behind a taxi when the taxi driver got out and slapped the front passenger-side window.
Information from: Los Angeles Times, http://www.latimes.com/