Pigs were used for steering wheel impacts because they have an internal structure similar to humans, and can be easily placed correctly via sitting upright in the vehicle. The ability to sit upright was an important requirement for test animals so that another common fatal injury among human victims, decapitation, could be studied. Additionally, it was important for researchers to be able to determine to what extent cabin design needed to be modified to ensure optimal survival circumstances. For instance, a dashboard with too little padding or padding that was too stiff or too soft would not significantly reduce head injury over a dash with no padding at all. While knobs, levers, and buttons are essential in the operation of a vehicle, it was essential to determine which design modifications would best ensure that these elements did not tear or puncture victims in a crash. Rear-view mirror impact is a significant occurrence in a frontal collision: How should a mirror be built so that it is rigid enough to perform its task, yet of low injury risk if struck?