This has happened to me several times over 35 years of driving, driving along at freeway speed and the car in front of me swerves at the last second to avoid a stationary object either car or mattress or very recently dropped material from a truck in the road. Usually there is a clue because you can most of the time you can see how other cars other than the one right in front of you is reacting unless the car ahead of you is much taller or has super dark tinted windows. I wonder how accurate LIDAR is through the rear window and front windshield of the car ahead of you.