One idea suggested in the patent is to mount airbags on the outside of the cars, to create a buffer for pedestrians. These airbags would deploy when the car senses that a collision with another vehicle is imminent. The patent notes that using traditional car bumpers and airbags would most likely cause a person to bounce off and injure themselves in the resultant collision with the ground. Google’s solution for preventing pedestrian injuries of this sort: bumpers made out of a “visco-elastic material.”
While the patent does not specify what that material could be, it most likely would be of a consistency somewhere between that of an earplug and memory foam.