The United States Department of Transportation's National Highway Traffic Safety Administration (NHTSA) recently released a Traffic Safety Facts - Research Note which summarizes the statistical date on lives saved by the implementation of seat belt laws and minimum drinking age laws. The note estimates that over 13,000 lives were saved by these provisions. The NHTSA is the division of the U.S. Department of Transportation which is responsible for highway and road safety. It is mandated with researching traffic safety measures, providing information, and forming regulations to make the roads safer.
The NHTSA considers lives saved to be one of the basic measurements of how effective safety devices, such as seatbelts, laws and regulations surrounding traffic safety are. They calculate the lives saved by comparing rates of compliance with the various laws and device usage numbers with changes in motor vehicle fatalities. Of course it is important to keep in mind that the numbers used to calculate the lives saved are only estimates, as it is impossible to know exactly what happened in every fatal accident and whether the lack of use or compliance with the relevant safety tool was the cause of the fatality.
The NHTSA estimated that in 2012 the use of seat belts in passenger vehicles saved approximately 12,174 lives up from 11,983 lives in 2013. They also predicted that if 100% of people used seat belts 3,031 lives would have been saved. This implies that there is still work to be done to stop preventable fatalities. As of 2012, forty nine states and the District of Columbia had seat belt laws in place. In thirty two of these states and the District of Columbia had primary laws requiring the use of a seatbelt. A primary seat belt law is one in which a car may be pulled over by the police and the driver fined solely for not wearing a seatbelt. In the remaining nineteen states the seat belt laws are what are referred to as secondary law states. In a secondary law state there must be another reason to pull the vehicle over. Motor vehicles in secondary states cannot be pulled over solely because their occupants or driver is not wearing a seatbelt. Statistics released by the NHTSA have shown that in states with primary laws concerning seatbelts the rate of fatalities involving injuries to non-restrained persons is less than in secondary state laws. This implies that there is a positive value in having stricter seat belt laws and particularly in having stricter enforcement measures for those laws.
Another measure of the effectiveness of road safety laws is looking at fatalities prevented due to minimum drinking age laws. The NHTSA estimates that minimum drinking age laws saved 525 lives in 2012. The NHTSA calculates the minimum drinking age laws effectiveness overall to be 13%. It does so by looking at a target age range, in this case 18-20 year olds, and calculating the reduction in involvement of those persons in fatal crashes. They look not only at the death of persons in that target age range but at all deaths that come from crashes and accidents when the driver is in the specified age range. So any accident where a person died and the driver was between 18-20 would be included in the calculation. Minimum drinking age laws are put in place by the states but the Federal Government incentivizes states to keep the minimum drinking age 21 or over by tying Federal funding of highways to it through the National Minimum Drinking Age Act. If a state does not implement a minimum drinking age of 21 or above that state will lose part of the highway funding it receives from the Federal government.
More information about estimating lives saved and the methodologies used in the NHTSA's report can be found in the Lives Saved FAQs. The Lives Saved FAQs goes into much more detail about the purpose of using lives saved as a measurement of effectiveness as well as into the methodologies of how the figures were arrived at.
The full results of the survey can be found on the NHTSA website.