The car has automatic cruise control of the sort fitted to many expensive cars such as Jaguars and BMWs. These use either radar or infrared beams fitted to the front of the car to measure the distance to the car in front. That distance is kept constant by automatic acceleration and braking.
But conventional automatic cruise control fails at speeds of less than 30kph (20mph). To circumvent this problem, the new car uses lidar—short for “light detection and ranging”—a measuring technology similar to radar but which uses laser beams rather than radio waves to measure distance and determine the speed of other vehicles. As light waves have shorter wavelengths than radio waves, the technology works at shorter distances and lower speeds. Indeed, the prototype has a distance-keeping system that will brake to a standstill, and move off again when the car in front moves.