Many state laws on car seats and seat belts may leave children unprotected and vulnerable to injuries caused in vehicle crashes, according to a new study published this week in Social Science and Medicine.

In the US, nearly 250,000 children are injured every year in car crashes, and approximately 2,000 die from their injuries, according to federal data. Most of these fatalities and injuries are preventable.

The study, examining  child passenger safety laws from 1978 to 2010 across all 50 states, found that many state laws lag behind existing research on vehicular safety and that great variation exists between states with regard to how a child should be restrained and in what device, and what the penalties are for non-compliance.

Some state child restraint laws, such as those in Arizona, Michigan, and South Dakota, cover children only up until the age of four, even though the American Association of Pediatrics recommends the use of child restraint devices until the vehicle seat belt fits them properly, which is typically when they have reached 4 feet 9 inches in height and are between 8 and 12 years of age.

"These laws do not keep up with the published evidence, and even when they do, there are some cases where the laws are unclear," said Jin Yung Bae, JD, MPH, the study's lead author, and associate research scientist at the Steinhardt School of Culture, Education and Human Development at New York University.

Bae also points to the laws covering infants and children of older ages as an example. Many of these laws fail to distinguish child passengers in need of rear-facing infant seats from those that should use forward-facing car safety seats or booster seats. In 2010, only 12 states explicitly required the use of booster seats while nine mandated infant seats and six required forward-facing car safety seats.

An interactive map of child restraint laws across all 50 states is available at: https://lawatlas.org/index.php/datasets/child-restraint

The research was conducted by a team from New York University (NYU), in collaboration with Temple University, and was supported by the Robert Wood Johnson Foundation through its Public Health Law Research (PHLR). The National Institute on Alcohol Abuse and Alcoholism, a part of the National Institutes of Health, also funded the study.

The researchers also identify the high number of exemptions that state laws grant as a limitation. As of 2010, 33 states failed to protect child passengers if the drivers are driving commercial passenger vehicles and 16 states exempted drivers that carry more children than their vehicle space can handle - as long as the drivers used restraint devices for as many children as the space allowed.

In addition, the study evaluates the adoption trend of child passenger safety laws. The researchers outline the rapid adoption of the earliest version of child safety seat laws in the late 1970s through the early 1980s, tracing the slower adoption of rear seating laws and minor seatbelt laws. As of 2010, the study finds that 35 states required seatbelt use for minor passengers and only 14 states required rear seating of child passengers.

Also significant is the lack of federal law governing the use of child safety seats - the federal government instead relies on funding and subsidies. This, the authors point out, has slowed progress of adoption, but has not curtailed it completely: "Even when there is no federal law in place, the states do catch up eventually," Bae explains.

The authors point to state alcohol laws as a comparison for how federal incentives may come into play. The researchers noted the legal terrain for child restraint laws differed sharply from that for state alcohol laws-and suggested that federal incentives may explain the difference.

For example, the number of states with 21-year minimum legal drinking age (MLDA) increased from 17 in 1984 to all 50 in 1988-four years after Congress passed the National MLDA Act conditioning states' enactment of such law to the continued full provision of the highway funds.

The study's authors were Jin Yung Bae, James Macinko, PhD, MA, and Diana Silver, PhD, MPH, of NYU Steinhardt's Department of Nutrition, Food Studies, and Public Health, and Evan Anderson, JD, of Temple's Center for Health, Law, Policy, and Practice.