They have been hailed as a technological revolution to alleviate the stresses of life on modern roads.

But it seems that driverless cars may in fact be the latest cause of tension for motorists, after it emerged that two out of six crashes with self-driving cars in California involved humans attacking them.

In one incident, a self-driving Chevrolet, operated by General Motors' Cruise driverless car division, was waiting at a traffic light for pedestrians to cross in San Francisco.

According to the California Department of Motor Vehicles (DMV), the robotic car's mere presence prompted a man to run across the street "against the 'do not walk' symbol, shouting, and [to strike] the left side of the Cruise AV's rear bumper and hatch with his entire body".