When drivers reach 30 mph, the WALKing man symbol transforms into a skeleton. The ad agency tasked with increasing safety by updating the signs says they were inspired by a statistic showing that mortality rates increase in auto/pedestrian accidents when the car is driving faster:
"Pedestrians struck by cars at 30 mph have an 80% chance of surviving the accident. A pedestrian struck by a car at 40 mph has a 70% chance of dying. When you are driving, that 10mph shift is subtle, but the effect it can have on a pedestrian is life or death," says Philip Stockton of Barbarian Group, the ad agency.