Self-driving cars are probably the future of road transportation, although how soon that will happen is anyone's guess. As far as we know they haven't made an appearance yet in Montana, but in California they have been extensively tested on public roadways. The California Department of Motor Vehicles recently released some data about accidents that have occurred in that state involving self-driving cars.
The data shows that self-driving vehicles are not immune from car accidents. They have been used on public roads since 2009, but the testing has only been officially authorized since September of last year. Google's cars have driven about 1.8 million miles and the company has acknowledged that its cars were involved in eight minor accidents between 2010 and mid-2014.
The data released by the California DMV relates to six accidents, five of which occurred when the cars were in self-driving mode. The sixth occurred just after the driver took control of the vehicle when he realized he was going to be hit by another car running a stop sign. All of the accidents were the fault of the driver of the other vehicle, and none resulted in injuries.
Sooner or later one of these cars will cause an accident while in self-driving mode that results in serious injury or death. When that happens, either the law of negligence or the law of products liability will apply. A driver who failed to take over control of the car when a reasonable driver would have done so might be found at fault. A body of law may develop that defines the circumstances when a driver should take control to avoid an accident. Alternatively, if there is evidence the accident was caused by a design defect in the vehicle or the software that controls it, the manufacturer or designer could be held responsible in a products liability lawsuit.
Source: Billings Gazette, "California reveals details of self-driving car accidents," Justin Pritchard, June 18, 2015