Restraint devices such as seat belts are a key element of motor vehicle occupant protection systems. According to the National Occupant Protection Use Survey (NOPUS), in 2016 there was a 90.1 percent front seat belt use rate for the nation as a whole, a 1.8 percent increase over the 88.5 percent reported in 2015. Front seat belt use was slightly higher among women (92.5 percent) compared with men (88.2 percent). Front passengers were more likely to use seat belts (90.1 percent) than rear seat occupants (80.6 percent). One strong determinant of seat belt use is the presence of a seat belt use law—states with a seat belt law that applied to all vehicle occupants had a rear seat belt use rate of 83.9 percent compared with 75.7 percent in states requiring front seat belt use only. In the United States, there were 10,428 unrestrained passenger vehicle occupants killed in traffic collisions in 2016, a 4.6 percent increase from 9,968 in 2015.