Transportation safety in the United States  Transportation safety in the United States encompasses safety of transportation in the United States, including automobile accidents, airplane crashes, rail crashes, and other mass transit incidents, although the most fatalities are generated by road accidents. The number of deaths per passenger-mile on commercial airlines in the United States between 2000 and 2010 was about 0.2 deaths per 10 billion passenger-miles. For driving, the rate was 150 per 10 billion vehicle-miles for 2000 : 750 times higher per mile than for flying in a commercial airplane. The U.S. government's National Center for Health Statistics reported 33,736 motor vehicle traffic deaths in 2014. This exceeded the number of firearm deaths, which was 33,599 in 2014. According to another U.S. government office, the National Highway Traffic Safety Administration (NHTSA), motor vehicle crashes on U.S. roadways claimed 32,744 lives in 2014 and 35,092 in 2015. (The National Center for Health Statistics may have different criteria for inclusion or a slightly different methodology from the National Highway Traffic Safety Administration.) The National Highway Traffic Safety Administration report comparing 2015 to 2014 said that fatalities increased from 2014 to 2015 in almost all categories: passenger vehicle occupants, passengers of large trucks, pedestrians, cyclists, motorcyclists, male and female, daytime and nighttime driving, and alcohol-impaired driving. Fatalities of drivers of large trucks remained unchanged. A NHTSA regression analysis of monthly roadway fatalities and various possible explanatory variables over the five-year period 2011–2015 showed the strongest correlation was with vehicle miles traveled (VMT), which had a correlation of .80, followed by average monthly temperature, which had a correlation of .74, meaning that higher temperatures were associated with increased fatalities. Part of the reason for that pattern may be that more people are out walking and biking in the warmer months, and pedestrians and cyclists are often victims of collisions with motor vehicles. The report also suggests that there may be more vacation travel during warmer months. The report does not say if the analysis was based on annual vehicle miles traveled or monthly vehicle miles traveled. Although not mentioned, motorcycle use, and therefore motorcyclist fatalities, may also increase in warmer months. The National Safety Council (NSC), a nonprofit safety advocacy group, estimates U.S. motor vehicle deaths in 2016 were 40,200, a 14% increase from its 2014 estimate. NSC counts traffic and non-traffic deaths within one year of a crash while the U.S. government agencies count only traffic deaths occurring within 30 days of a crash.