Main use of lidar is for very fast obstacle detection. Other popular methods to detect obstacles are ultrasonics and vision. Problem with ultrasonics is latenc

Main use of lidar is for very fast obstacle detection. Other popular methods to detect obstacles are ultrasonics and vision. Problem with ultrasonics is latency, range as well as lack of accuracy. To detect obstacles with vision, generally you need stereo camera and generate disparity map (you can do with moving mono camera too but its much harder and even more unreliable). The confidence levels drops quickly as objects are farther and lighting conditions, reflections etc gets more complex. The main problem is that popular algorithms only rely on geometry to compute the depth and they don't into account knowledge of the world. For example, if there is area of specular reflection, geometry will fail even though one can reasonably estimate depth by assuming some continuity of shape of objects in real world. We humans are very efficient in figuring out depth even with single eye and its purely because we can do very quick and accurate object segmentation and combine it with our knowledge of what those objects are (semantics) as well as our internal map of the world around us. For example, when you see truck on the road even with single eye, you have fair estimate of what sizes trucks usually are and how big should it appear if it was 100ft away vs 1000ft away. You would be able to do this even if you can see truck only partially from the side angle or back angle. There is no known algorithms currently that can come anywhere close to human level accuracy and speed for depth estimation and consequently obstacle detection using just vision in variety of lighting conditions when you are moving at 70 miles/hr. On the other hand, lidars are super easy to implement, fast and very accurate. So unless a major breakthrough comes along, lidars are actually the only choice right now for fast and accurate obstacle detection. Remember even a tiny error rate could be fatal when you have millions of cars covering millions of miles every day.