Seatbelt use among Americans has continued its two-decade-long uptick throughout 2012.

According to an annual study by the National Highway Traffic Safety Administration, 86 percent of drivers and passengers use them, a 2 percent improvement over last year.

The South saw the biggest increase: 85 percent of drivers in those parts now buckle up, which is 5 percent more than in 2011. Midwesterners buckle up in comparable numbers, while the Western states are the most impressive, with 94 percent of the car-riding population using seatbelts. Northeasterners lag behind; just 80 percent wear their belts.

Why the differences?

"Seatbelt use continued to be higher in the states in which vehicle occupants can be pulled over solely for not using seatbelts ('primary law states') as compared with the states with weaker enforcement laws ('secondary law states') or without seat belt laws," according to the NHTSA report.

Thirty-two states and the District of Columbia have primary laws, while secondary laws are in place in 17 states. New Hampshire essentially has no seatbelt law at all; occupants over 18 can ride unrestrained.
 
The study also showed that car occupants in urban areas are slightly more inclined to wear belts than those in rural regions, while suburbanites are the most likely to buckle up. Also, pickup-truck drivers aren't bastions of seatbelt use; just 77 percent strap themselves in.

Fog is the weather condition most likely to inspire drivers and passengers to use their seatbelts, and heavy traffic sees 89 percent of occupants belted up -- a 15 percent improvement over light traffic. Highways see significantly higher belt usage than surface streets.

The research also shows that, most importantly, seatbelts are an effective safety precaution. As usage has steadily risen since 1994, fatalities of unrestrained vehicle occupants during daytime driving hours has plunged, according to NHTSA.

[Source: NHTSA]