Preventing Concussions in Motor Vehicle Crashes

In the past 10 years, traffic deaths have dropped by about 25 percent (NHTSA 2015b), which is a remarkable public health improvement in a short period of time. Even so, nearly 90 people die and 2.3 million are injured every day in motor vehicle crashes in the United States (NHTSA 2015c). The Centers for Disease Control and Prevention estimates that motor vehicle crashes are the country’s third leading cause of traumatic brain injury (TBI) and the leading cause of death from TBI (Faul et al. 2010).

The mission of the National Highway Traffic Safety Administration (NHTSA) is to save lives, prevent injuries, and reduce the economic burden associated with motor vehicle crashes. To that end, the agency tracks data, conducts research, administers safety grants to states, and proposes federal standards to enhance traffic safety.

The Work of NHTSA

The two primary areas of concern for NHTSA are the safety of vehicles and the behavior of drivers and road users. Our work in these areas is based on data derived from crashes—behavioral and vehicle factors leading up to the crash, how the vehicle behaves in the crash, how the occupant interacts with the inside of the vehicle during the crash, and the injury consequences.

Federal Safety Standards

NHTSA sets federal motor vehicle safety standards for vehicles sold in the United States. One of the measures used to assess the performance of vehicles in crashes is the head injury criterion (HIC), a measure of linear acceleration that we use for research and regulatory purposes.

A number of NHTSA standards are based on the HIC, and they have been quite successful in reducing concussion and other serious injury as well as fatalities. For example, the addition of interior padding in vehicles has saved about 35,000 lives since it was introduced in the late 1960s, and seat belts have saved about 330,000 lives over the same time period—really remarkable for a relatively simple device. Child restraint systems have saved about 10,000 lives (Kahane 2015), and side impact protection has saved about 35,000 lives. Ejection mitigation technologies, which include curtain airbags, were recently introduced and have already saved hundreds of lives (Kahane 2014).

It is difficult to calculate cumulative numbers for motorcycle helmets, but we estimate that in 2014 they saved about 1,600 lives (NHTSA 2015a).

Crash Data Collection

Since the 1970s NHTSA has collected detailed information on every traffic fatality in the United States. The Fatality Analysis Reporting System (FARS) includes several hundred data elements on each crash. Complementing this census of roadway fatalities is a crash sampling system that can provide detailed information on injuries associated with vehicular crashes.

NHTSA has also established six crash research centers around the country as part of a Crash Injury Research and Engineering Network (CIREN). Each CIREN center typically involves a medical school and an engineering school working together to research about 50 crashes per year and publish their data and analysis.

Based on its extensive injury research, NHTSA is developing a brain injury criterion, which includes a rotational element that will complement the linear HIC measurements. Researchers hope that these measures and criteria will make it possible to better design the interior of vehicles—and reduce the number of fatal car crashes, which currently account for more than 32,000 deaths per year (NHTSA 2015c).

The Role of Behavior

Human behavior is by far the weakest link in motor vehicle safety. Our research indicates that 94 percent of all crashes are caused by driver factors; the vehicle is a factor in only about 2 percent of crashes, the roadway in about 2 percent, and other factors, including weather, account for the remaining 2 percent (Singh 2015) (figure 1). NHTSA therefore examines opportunities to change behavior to prevent crashes.

Figure 1

Seat Belt and Helmet Use

The reluctance of many vehicle occupants to use seat belts and of motorcycle riders to wear compliant helmets costs lives. Seat belt use rates are now at 87 percent; 100 percent use would save 2,800 more lives annually. Universal use of motorcycle helmets could save more than 700 additional lives per year. These are very low cost interventions that have high-value potential returns.

A further important objective is to increase use of motorcycle helmets that meet the Federal Motor Vehicle Safety Standards. A significant portion of motorcycle riders choose not to wear helmets certified to meet the safety standard, instead wearing noncompliant helmets that are fashionable but provide very little protection in a crash (figure 2). NHTSA recently issued a Notice of Proposed Rulemaking (NHTSA 2015a) that aims to prevent manufacturers from selling helmets that do not meet the safety standards.

Figure 2

Technology to Address Behavioral Challenges

NHTSA and other researchers are identifying ways to address risky behaviors through technology.

Alcohol-impaired driving accounted for 31 percent (9,967) of all traffic fatalities in 2014 (NHTSA 2015c). The ignition interlock is a technology that prevents repeat offenses of driving while impaired. It requires a driver to breathe into the device before starting the vehicle; if the driver’s blood alcohol concentration is above a preset limit the ignition interlock will not allow the vehicle to start. Research has shown that, while installed on an offender’s vehicle, interlocks reduce repeat offenses among both first-time and repeat offenders, and even predict the risk of repeat offenses after removal (Mayer 2014).

By 2014 all states had enacted legislation requiring or permitting the use of interlocks to prevent alcohol-impaired driving. Laws and procedures vary by state, but interlocks are generally required after arrest, may be removed after a certain period of time, and may be a condition of reinstatement of a suspended license (Mayer 2014).

The Role of Emerging Technologies

The long-term solution to motor vehicle crashes may eventually be automated and driverless vehicles. Experimental vehicles now show great promise, but much research and development are needed to ensure their safe and reliable operation on a widespread basis on the roads.

NHTSA and other organizations are pilot testing vehicle-to-vehicle (V2V) and vehicle-to-infrastructure communication systems that use crash avoidance technology to warn drivers about dangerous situations that could lead to a collision. For example, V2V could warn that a vehicle up ahead is braking and the driver needs to slow down, or that it is not safe to proceed through an intersection because another car, unseen by the driver, is quickly approaching (NHTSA 2014).

In the meantime, a number of currently available driver warning systems can compensate for lack of attention and driving-skill problems. For example, some vehicles are now equipped with lane departure warning systems, and many cars have brake-assist systems and even automatic emergency braking systems. Increasingly, there will be opportunities for technologies to assist drivers in other safety-sensitive tasks.

These and other safety systems will be highlighted in NHTSA’s New Car Assessment Program to educate consumers and increase demand for these important features. Driver assistance and automation systems are very promising, but the judgment, vigilance, and skill of drivers and other users remain crucial to improve road safety for the foreseeable future.

References

Faul M, Xu L, Wald MM, Coronado VG. 2010. Traumatic Brain Injury in the United States: Emergency Department Visits, Hospitalizations and Deaths 2002–2006. Atlanta: Centers for Disease Control and Prevention, National Center for Injury Prevention and Control.

Kahane CJ. 2014. Updated Estimates of Fatality Reduction by Curtain and Side Air Bags in Side Impacts and Preliminary Analyses of Rollover Curtains. Report No. DOT HS 811 882. Washington: National Highway Traffic Safety Administration.

Kahane CJ. 2015. Lives Saved by Vehicle Safety Technologies and Associated Federal Motor Vehicle Safety Standards, 1960 to 2012: Passenger Cars and LTVs, with Reviews of 26 FMVSS and the Effectiveness of Their Associated Safety Technologies in Reducing Fatalities, Injuries, and Crashes. Report No. DOT HS 812 069. Washington: National Highway Traffic Safety Administration.

Mayer R. 2014. Ignition Interlocks: A Toolkit for Program Administrators, Policymakers, and Stakeholders, 2nd ed. Traffic Safety Administration. Report No. DOT HS 811 883.Washington: National Highway Traffic Safety Administration.

NHTSA [National Highway Traffic Safety Administration]. 2014. V2V Fact Sheet. Washington. Available at www.safercar.gov/staticfiles/safercar/v2v/V2V_Fact_Sheet_ 101414_v2a.pdf.

NHTSA. 2015a. 80 FR 29457 – Federal Motor Vehicle Safety Standards: Motorcycle Helmets (May). Federal Register 80(98):29458–29487. Available at www.gpo.gov/fdsys/granule/FR-2015-05-21/2015-11756.

NHTSA. 2015b. Traffic Safety Facts (July). Washington.  Available at www-nrd.nhtsa.dot.gov/Pubs/812169.pdf.

NHTSA. 2015c. 2014 Crash Data Key Findings. Report No. DOT HS 812 219 (November). Washington. Available at www-nrd.nhtsa.dot.gov/Pubs/812219.pdf.

Singh S. 2015. Critical Reasons for Crashes Investigated in the National Motor Vehicle Crash Causation Survey. Report No. DOT HS 812 115. Washington: National Highway Traffic Safety Administration.