More than 11 million large trucks (trucks weighing over 10,000 pounds) travel U.S. roads, and almost 4 million operators hold commercial driver's licenses. In 2015, large trucks were involved in more than 400,000 motor vehicle crashes serious enough to be registered by police, with nearly 100,000 of those crashes causing injuries and around 3,600 resulting in fatalities. To address this situation, Congress has assigned the U.S. Department of Transportation (DOT)—primarily the Federal Motor Carrier Safety Administration (FMCSA)—responsibility for regulating the safety practices of commercial motor carriers and drivers. In addition, the National Highway Traffic Safety Administration (NHTSA) in DOT is responsible for the safety of the vehicles themselves through its role in setting vehicle safety standards. This responsibility involves oversight of an industry comprising over 500,000 motor carriers, with around 35,000 new carriers beginning operation and many existing carriers exiting the industry each year. The agencies concerned with truck safety are relatively small; FMCSA has 1,175 full-time-equivalent personnel, including 600 front-line enforcement staff, and NHTSA personnel are involved in truck safety primarily at times when vehicle safety standards are under consideration. Truck safety efforts are assisted by roughly 12,000 state employees, including highway patrol officers. Federal enforcement agents and state agents enforcing federal regulations conduct over 3.5 million roadside inspections of trucks and buses annually, as well as over 16,000 on-site investigations and over 30,000 safety audits of new motor carriers. Some 10,000 motor carriers and drivers are the subject of FMCSA enforcement actions each year. Freight rates and other economic matters are not subject to federal regulation. Although crashes involving unsafe trucks or drivers often lead to public outrage, regulatory efforts to improve truck safety are often controversial. Truck safety laws and regulations directly affect the profitability of hundreds of thousands of companies, most of them small, and the livelihoods of millions of commercial drivers. Trucking regulations may also affect the cost of freight to shippers and alter the competitive balance between the trucking industry and its railroad and barge competitors. Both government and private-sector analysts have forecast significant increases in trucking activity over the coming decades, reflecting expected growth in the U.S. economy and the role of trucks in moving freight. For example, DOT projects a 43% increase in freight ton-miles carried by truck between 2012 and 2040. Greater truck mileage could result in increasing numbers of truck crashes. Some say various safety technologies now under development, culminating in "self-driving" trucks, may eventually make truck crashes less common. This report briefly reviews heavy truck safety trends, then looks at FMCSA's role in promoting safety in the heavy truck industry. It then divides heavy truck safety issues into three categories, and addresses each in turn: issues related to motor carriers (the companies that make up the industry, the majority of which have only a handful of vehicles); issues related to the vehicles themselves; and issues related to commercial drivers. The crash rate for large trucks, measured as the number of crashes involving fatalities, injuries, or property damage per million vehicle miles traveled, has declined over time. Crash rates typically drop significantly during recessions and then rise as economic growth resumes; this dynamic was evident during the 2010-2014 period, as truck crash rates rose from their historic lows during the 2007-2009 recession ( Figure 1 ). Nonetheless, the crash rate in 2014, the most recent year for which data are available, was still below the pre-2007 level. The number of people killed in crashes involving large trucks increased by 4% from 2014 (3,908) to 2015 (4,067), although it is still unknown whether the fatality rate per million vehicle miles traveled increased. Only additional data will reveal whether the long-term decline in the truck crash rate has run its course. If so, this could indicate that the safety performance of large trucks is decreasing, raising questions about FMCSA's ability to further improve truck safety. Historically, trends in truck crashes resulting in fatalities, in injuries, and in only property damage have been roughly similar. However, in recent years the fatal crash rate has been relatively steady while the rates of crashes involving injuries and property damages have risen. The vast majority of fatalities in crashes involving large trucks are experienced by the occupants of the other vehicle(s), typically passenger vehicles. Safety improvements to cars and light trucks, such as the increasing number of airbags, may be reducing the number of fatalities from truck-car collisions. According to an FMCSA study, two-thirds of commercial truck crashes are caused by the other driver, not the commercial driver. This finding implies that additional attention to truck driver behavior would be relatively ineffective in reducing the number of crashes involving large trucks. However, some critics question the validity of the proportion of crashes caused by commercial drivers, noting that crashes between commercial and noncommercial vehicles kill noncommercial drivers more frequently than the commercial drivers, often leaving investigators with only the commercial driver's account of the crash. Thus, these critics assert, the proportion of crashes attributed to noncommercial drivers may be overstated. Congress established FMCSA as a separate administration within DOT through the Motor Carrier Safety Improvement Act of 1999 ( P.L. 106-159 ), transferring responsibilities that had previously been handled by an office within the Federal Highway Administration. FMCSA's responsibilities can be divided into two parts: creating and enforcing safety rules and regulations, and implementing programs and procedures to promote the safety of motor carriers, commercial vehicles, and drivers. The constitutional provision granting Congress the power to regulate interstate commerce has been construed to give the federal government much greater authority over commercial vehicles and drivers engaged in interstate commerce than over commercial vehicles not engaged in interstate commerce. Commercial vehicles that typically operate within a single state, such as waste haulers and cement mixers, are generally not subject to federal safety regulations. Regulation of intrastate commercial transportation is generally a state matter. So, for example, Congress has long required that commercial drivers in interstate commerce must be at least 21 years of age, but most states allow a person to get a commercial driver's license (CDL) starting at age 18. This has resulted in a population of 18- to 20-year-olds who have CDLs but may operate commercial vehicles only within the state that issued their license. Congress can affect the operations of intrastate carriers indirectly, by encouraging states to adopt laws that govern them. In addition to licensing truck drivers, FMCSA reviews trucking companies to check their compliance with federal requirements and audits the safety practices of companies entering the industry. Although FMCSA has authority to conduct roadside safety inspections of trucks, it usually relies on state law enforcement personnel for that purpose. State officials also conduct many compliance reviews and new entrant safety audits. In creating FMCSA, Congress specified that its intent was the furtherance of the highest degree of safety in motor carrier transportation, and that FMCSA should consider safety as the highest priority. Congress required FMCSA to develop a long-term strategy for improving commercial motor vehicle, operator, and carrier safety, including a schedule and an annual plan for achieving certain goals set by Congress. FMCSA publishes an updated strategic plan periodically; the annual implementation plan is submitted to Congress as part of the annual budget process. In 1999, Congress established a two-pronged approach to improving the safety of new entrants to the motor carrier industry. It required FMCSA to conduct a safety audit of each new entrant within 18 months of starting operations, and it directed FMCSA to establish minimum requirements for firms wishing to enter the industry to ensure that they know the federal safety standards before they are granted registration. The latter directive included a requirement that DOT consider establishing an examination that would test officers of new applicants on their knowledge of federal safety standards. FMCSA has not yet determined that new entrants should have to pass such an exam. In 2015, Congress tightened these requirements, directing FMCSA to audit new entrants within 12 months of their entry into the industry. The focus on new entrants is due to studies finding that new entrants to the motor carrier industry have lower rates of compliance with basic safety management requirements than do experienced carriers. FMCSA observed that the shortened time frame will increase its audit workload. An average of more than 35,000 firms enter the industry each year, but a certain percentage of carriers typically go out of business between months 12 and 18. The 12-month deadline requires FMCSA to audit many carriers that will go out of business soon after the audit. Under current practice, a new trucking firm may engage in interstate commerce before FMCSA conducts a safety assessment. In August 2009, in response to a petition from Advocates for Highway and Auto Safety, FMCSA issued an Advanced Notice of Proposed Rulemaking in which it requested information on the costs and benefits of requiring new entrants to pass an examination of their knowledge of federal safety requirements, and of alternatives to a proficiency exam that would also improve the safety performance of new entrants. In September 2009 FMCSA's Motor Carrier Safety Advisory Committee, made up of industry representatives, recommended that FMCSA take a number of steps to ensure that new entrant motor carriers are knowledgeable about safety requirements, including testing. The Advanced Notice of Proposed Rulemaking continues to be listed in DOT's monthly report on the status of significant rulemakings, but FMCSA has taken no further action. The Commercial Vehicle Safety Alliance (CVSA), an association of federal, state, and local commercial motor vehicle safety officials and industry representatives, has recommended that Congress request a study of the costs and benefits of expanding the new entrant safety assurance program to include intrastate carriers.