What are some of the biological features that humans have developed that the early mammals did not possess?

Your Inner Reptile" traces our hair, skin, teeth, jaws and sense of hearing back to reptilian ancestors — from ferocious beasts that ruled the Earth to a little shrew-like animal that lived 195 million years ago.

the answer is; comparing the frequency of collisions with and without the device

this makes the anti-collision system an independent variable and the collisions a dependent variable. if there are fewer collisions with an anti-collision system that without, then it can be stated that the system is a success. essentially, collisions under an anti-collision system are compared with the frequency of collisions by cars with the human drivers.