While the number of motor vehicle fatalities in the United States has been on the decline for more than a decade now, car crashes is still one of the leading causes of death, particularly among the younger population. However, car accident-related injuries are not the only health impact of car use, as motor vehicle emissions also pose a major threat to public health. It has long been known that there are numerous public health risks associated with motor vehicle emissions, but so far, no one has ever done a study comparing the impact of auto emissions and car crashes on overall public health, that would help determine which of them causes more deaths.

That’s the question that David Levinson, the prominent transportation analyst who currently works as a professor at the University of Minnesota, tried to answer in a post on his blog Transportationist, where he claims that while authorities say that the number of crash-related fatalities is higher than deaths attributed to air pollution from cars, it depends largely on which metric is used when comparing the number of deaths. He used data from the National Highway Traffic Safety Administration (NHTSA) to see how many people died in traffic accidents in 2005, and compared it against the number of deaths caused by air pollution from cars for the same year, based on a study conducted by a group of researchers from MIT.

Levinson found that in 2005, there were 43,510 car crash fatalities in the U.S., which amounts to 14.7 deaths per 100,000 Americans. According to the MIT study, almost 52,800 deaths were associated with particulate matter from traffic – a rate of nearly 18 per 100,000 Americans. This means that air pollution from road transportation was responsible for 19 percent more fatalities than car crashes in 2005, making it significantly deadlier. What’s more, the study also says that pollution from road transportation represents the largest share of all emissions-related deaths, which is yet another indication of the serious health impact of car use.

On the other hand, car crashes can be considered deadlier if Years of life lost is taken into account as a parameter. Levinson cites a study by the Global Burden of Disease, saying that in 2010, 653 years of life per 100,000 Americans were lost to transportation-related injury, as compared to 565 that were attributable to air pollution. He explains that the reason for the larger number of years of life lost to road injury is the fact that the vast majority of people killed in car crashes are young people, so accidents shorten life more drastically.

The main takeaway from Levinson’s analysis is that in order to improve overall public health, authorities need to start paying much more attention to the negative effects of carbon dioxide emissions from motor vehicles, and boost efforts for reducing emissions, instead of just focusing on enhancing road safety, since the impact of car use goes beyond car crash-related injuries.