From a purely stats pov, in situations where the confusion matrix is very asymmetric in terms of what we care about (false negatives are extra bad), you generally want multiple uncorrelated mechanisms, and simply require that only one flips before deciding to stop. All would have to fail simultaneously to not brake, which becomes vanishingly unlikely (p^n) with multiple mechanisms assuming uncorrelated errors. This is why I love the concept of Lidar and optical together.