One positive effect of recycling aluminum cans to manufacture new beverage containers is 1) conserving earths resources 2) creating acid rain 3) warming earths atmosphere or 4) increasing the ozone layer

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.