In 2010, the federal government set a target of 92 percent of Americans using seat belts while driving or riding in cars by the year 2020. A new study by University of Washington researchers finds that most American counties weren't meeting that benchmark in 2012, and that regional variations in seat belt use can be explained in part by how authorities enforce seat belt laws.

First, the data: Here's the map of county-level seat belt use in 2012, modeled using data from the nationwide Behavioral Risk Factor Surveillance System:

Counties in blue are already at 92 percent seat belt prevalence or higher, meaning they met the federal guideline eight years ahead of deadline. Great work, drivers on the west coast, and parts of Texas and Maryland! On the other hand, the other colors indicate places along the gamut from just barely missing the federal target (yellows) to not even coming close (oranges to red).

Drivers and passengers in the northern plains, for instance, tend to wear their seat belts about half the time. Overall the trend seems to be higher seat belt use in urban areas and fewer seat belts out in the country.

The researchers behind the study point out that state-level policies might have something to do with this. In some states, like the Dakotas and Nebraska, seat belt use is a “secondary enforcement” priority, meaning police can only ticket drivers for not wearing seat belts if they've already pulled them over for something else, such as speeding. Those areas tend to have lower rates of compliance.

On the other hand, in places such as Washington, Oregon and California, seat belt use is a primary enforcement priority, meaning you can be pulled over simply for not wearing your seat belt. Those states have some of the highest rates of seat belt use.

The researchers noted one other main factor that appeared to affect seat belt use: gender. Women (89.6 percent) are more likely to wear their seat belts than men (81.9 percent).

Nationally about 85.9 percent of Americans regularly wear their seat belts, according to the study. Or, to put it another way: About 14 percent don't. But the people who don't wear seat belts make up a disproportionate share of traffic fatalities: The unbelted make up roughly half of all motor vehicle fatalities, according to the National Highway Traffic Safety Administration.