Status of Road Safety and Injury Burden

Overall morbidity and mortality from road traffic accidents in the United States and Canada have declined over the last several decades since their peak in the 1970's. This progress has been attributed to active surveillance, improved road and vehicle safety, injury prevention and laws enforcing safer driving behaviors. Although there have been notable successes, a number of ongoing and new challenges remain. A key component of successful programs to combat injuries in North America is active, government-funded surveillance programs. In the United States, surveillance is conducted by the National Highway Traffic Safety Administration (NHTSA), a branch of the Department of Transportation that was established in 1970. Vehicular fatalities are reported to the Fatality Analysis Reporting System, whereas nonfatal injuries are recorded in the National Automotive Sampling System, a nationally representative probabilistic sample based on police reported data that uses the Maximum Abbreviated Injury Scale (MAS3+). The budget of NHTSA is over 800 million dollars with an estimated $148 million for vehicle safety, $118 million for behavioral safety, and $560 million for enforcement.1 A similar system exists in Canada through the Road Safety Directorate of Traffic Canada. In 2011, there were 32,367 fatal crashes and 1.5 million injuries as a result of road traffic crashes in the United States, which is the lowest number of fatalities since 1949. The majority of victims killed in traffic crashes were drivers (51%), followed by passengers (18%), motorcyclists (14%), pedestrians (14%), and bicyclists (2%).2 At the last estimate in 2001, the economic impact was $231 billion dollars as a result of fatalities ($41 billion), injury and disability ($130 billion), and property damage ($60 billion).3 This represents $820 per US citizen and 2.3% of US gross domestic product. In Canada, traffic crashes cost an estimated $23 billion dollars, which is 2.0% of gross domestic product.4 As in most developed countries, there has been a trend toward fewer fatalities from traffic crashes in the United States. However, traffic fatalities from 1979 to 2000 declined by approximately 50% in Canada, the United Kingdom, and Australia, the decline in the United States was more modest at 18%.5 In the 1990's and early 2000's, there was a plateau in the US fatality rate followed by a fairly dramatic decline from 2006 to 2011, which corresponded in part to a reduction in vehicle use because of the economic downturn.4 However, it is noteworthy that in 2011, the fatality rate per 100 million vehicle miles traveled was 1.10, a historic low, suggesting that other factors contributed to the decline.4 The rate of nonfatal injuries because of crashes has concurrently declined by 28% since 1990.4 Although fatalities for other categories of road users (motor vehicle occupants, pedestrians, and cyclists) declined over the last 2 decades, motorcycle fatalities have increased 42% in the United States since 1990.4 This has been attributed in large part to a rise in motorcycle ownership and usage, particularly in the age group between 40 and 44 years.6 In contrast to many other high-income countries, including Canada, the United States does not have a national law mandating motorcycle helmet use. Currently, only 19 states and the District of Columbia require helmets for all occupants and passengers of motorcycles, and the estimated rate of helmet usage is 60% nationally.4,7 This area therefore holds significant potential because helmets have been shown to reduce mortality by 42% and head injury by 69% among motorcyclists in a recent Cochrane review.8 The majority of US states (32 and District of Columbia) have primary seat belt laws, meaning that a driver may be cited for lack of seat belt use in the absence of another offense. This has led to improvement in rates of seat belt usage in states with primary laws (90%) compared with states without (76%). Overall, the rate of seat belt usage in the United States rose from 71% to 86%, from 2000 to 2012; however, it remains lower than many other developed countries.4 The percentage of fatalities involving unrestrained passengers in the United States is 52% compared with 36% in Canada, where the seat belt wearing rate is 96%, and primary seat belt laws are present in all provinces.4 A particularly problematic population is teenagers between the ages of 15 and 20 years, among whom the number one cause of death is road traffic crashes.9 Sixteen-year-old drivers are 5 times more likely than 18-year-olds to be involved in fatal crashes.9 Graduated licensing programs for new drivers were initiated in many states to combat this problem. These programs typically involved a staged system that includes a learning phase and an intermediate phase that require variable amounts of supervision while driving and limit night-time driving and the number of passengers in the vehicle. Based on fatality analysis reporting system data, it has been estimated that graduating licensing programs reduce fatalities among 16 and 17-year-olds by 20%.10,11 At the other end of the age spectrum, older adults have become of greater concern with an aging baby boomer generation. Although the number of miles driven among this demographic is lower, the rate of crash involvement per mile and the susceptibility to fatal injury is higher.4 Laws surrounding license renewal and vision screening are highly variable in the United States. For example, conducting a vision test is mandatory with license renewal beginning at the age 40 in Maryland compared with 80 in Virginia.12 Cognitive screening has been suggested as another method to reduce at-risk older drivers; however, at least 1 study has shown higher mortality rates among older adults because of use of other forms of transportation.13 Additional research is needed to establish effective methods to protect older road users. One of the commonest contributing factors to traffic crashes is alcohol intoxication, which was involved in 31% of fatal crashes in the United States in 2011.4 The legal maximum blood alcohol content in the United States and Canada is 0.8 g/L; however, the majority of provinces in Canada enforce a level of 0.4–0.5, as do the majority of developed countries worldwide.4 There are 2 relatively new technologies that may effectively reduce drunk driving: ignition interlock technology and continuous alcohol monitoring (CAM) devices. Ignition interlock technology is a breath testing device that connects to the vehicle ignition and prevents intoxicated drivers from starting the vehicle. These devices have been shown to reduce repeat offenses by 35%–90%, which is more effective than license suspension.14,15 However, to date, these have primarily been used for recurrent offenders or as an optional alternative to license suspension.14 CAM is a relatively new technology that uses an ankle bracelet that measures alcohol in perspiration to monitor alcohol consumption, which is relayed to a secure central Web site. Unfortunately, the literature surrounding the effectiveness of CAM technology remains limited.15 A major public health focus recently relates to the proliferation of mobile phones and their potential to cause road traffic injuries because of distraction. In the United States, in 2011, there were 3331 deaths (10% of all crash fatalities) attributed to distractions, of which, 12% were attributed specifically to mobile phone use.16 Awareness campaigns and laws prohibiting mobile phone use while driving may help to mitigate this growing problem. In addition to addressing human factors, there have been important advances in vehicle safety along with several new technologies that hold great promise. Air bags have been shown to reduce mortality in crashes by 19%17 compared with safety belts alone. New technologies include computer-driven crash avoidance and mitigation systems that automatically detect an impending crash and either provide warning, brake the car, or both.18 These systems may be further advanced by car-to-car electronic communication systems. Both technologies are currently considered high priorities of the NHTSA, but research establishing their effectiveness is pending more widespread use.18 In summary, although definite progress has been made in North America with respect to traffic safety, a number of potential targets for improvement remain. In the United States, the federalist system of allowing individual states to make traffic laws has perhaps slowed the uptake of policies proven to reduce fatal and nonfatal injuries on a national level. Driving behaviors, such as drug and alcohol use, helmet and seat belt usage, and distracted driving remain a primary target for prevention strategies. At the same time, new technologies to improve vehicle safety hold great promise in further reducing the burden of road traffic injuries in North America.

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