All clinical research must be interpreted in its historical context. For studies of motor vehicle occupants, that context has been changing particularly quickly.
Once upon a time, not so very long ago, children were always loose when riding in cars. It was not until 1968 that seat belts were required in cars at all.1 The very first child passenger restraint law for preschool children went into effect in Tennessee in 1978. The 50th state passed its law in 1984. Surveys by the National Highway Traffic Safety Administration indicated that in 1979, 15% of child passengers 0 to 4 years old were restrained compared with 49% in 1984.2
The expectation that children should be protected when they ride in cars, a fairly new one for our society, is already sufficiently strong that car safety seat use among young children now approaches that of immunizations: in
CHRISTOFFEL KK. Child Passenger SafetyPast, Present, and Future. Am J Dis Child. 1989;143(11):1271-1272. doi:10.1001/archpedi.1989.02150230029015