One important research objective that could not be achieved with either cadavers or live humans was a means of reducing the injuries caused by impalement on the steering column. By 1964, over a million fatalities resulting from steering wheel impact had been recorded, a significant percentage of all fatalities; the introduction by General Motors in the early 1960s of the collapsible steering column reduced the risk of steering-wheel death by fifty percent. The most commonly used animal subjects in cabin-collision studies were pigs, primarily because their internal structure is similar to a human's. Pigs can also be placed in a vehicle in a good approximation of a seated human.