Beginning in 1966 all new cars sold in Morodia were required to have safety belts and power steering  Previously, most cars in Morodia were without these features  Safety belts help to prevent injuries in collisions, and power steering helps to avoid collisions in the first place
But even though in 1966 one-seventh of the cars in Morodia were replaced with new cars, the number of car collisions and collision-related injuries did not decline
Because of a driver-education campaign, most drivers and passengers in cars that did have safety belts used them in 1966.