Waymo put a ton of sensors, including lidar and cameras, to create a truly driverless experience. Tesla put a ton of cameras to make a mostly driverless experience (but when you need a driver you NEED a driver). Comma strapped a cellphone cam to the windshield to make a semi driverless experience on straightish roads, and a driver must take over when anything complex happens. Source: very happy comma.ai user for many years now