US regulators have launched an investigation into Tesla’s Full Self-Driving (FSD) software after a number of crashes were reported when it was being used in an area of reduced road visibility.

Rather than using expensive lidar hardware – the approach favoured by other driverless tech firms such as Google’s sister firm Waymo – Tesla’s Autopilot uses cameras, ultrasonic sensors and radar to see and sense the environment around the car.

Tesla has said Autopilot enables vehicles to steer, accelerate and brake within their lanes, while FSD lets vehicles obey traffic signals and change lanes. The company has said both technologies “require active driver supervision” with a “fully attentive” driver whose hands are on the wheel and that they “do not make the vehicle autonomous”.

However, the National Highway Traffic Safety Administration (NHTSA) has long expressed doubts regarding whether the company adequately ensures that drivers pay attention when using the driver assistance system.

In a recent...