https://www.sciencedaily.com/releases/2019/04/190423145508.htm

The laser sensors currently used to detect 3D objects in the paths of autonomous cars are bulky, ugly, expensive, energy-inefficient -- and highly accurate.

These Light Detection and Ranging (LiDAR) sensors are affixed to cars' roofs, where they increase wind drag, a particular disadvantage for electric cars. They can add around $10,000 to a car's cost. Despite their drawbacks, most experts have considered LiDAR sensors the only plausible way for self-driving vehicles to safely perceive pedestrians, cars and other hazards on the road.