[energy123]

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.

[red75prime]

The true self-driving trolley problem. How many rear-end collisions and riders' annoyance caused by phantom braking a manufacturer (or a society) is going to tolerate to save one child per N million miles?

Uncorrelated approach improves sensitivity at the cost of specificity. Early sensor fusion might improve both (maybe at the cost of somewhat lesser sensitivity).