The launch this week of Uber’s “self-driving fleet” of taxis in Pittsburgh marks the first time that members of the public have been able to experience a self-driving car. While these are not fully autonomous vehicles — the driver is able to intervene — they are capable of driving themselves. Their trial run could be a first step to normalising their presence on American roads.

In a sense, semi-autonomous cars are hardly a new thing for US drivers. Manufacturers like Tesla have been dreaming up gizmos that make it easier for drivers to chill out at the wheel. A fatal accident this year that involved one of the electric carmaker’s “assisted” vehicles is a reminder of the safety risks inherent when machines do the driving. One is that the cameras on which the vehicle depends to gauge its position when manoeuvring are not always fail safe. Another is a false sense of security for drivers who pay less than full attention because of the perception that the car is capable of driving itself without any human intervention.

In the absence of clear safety rules, these cars raise pressing questions that need to be resolved. Car manufacturers are split over whether hands-off driving should be allowed even if a car is driving itself.