The National Transportation Safety Board (NTSB) was established in 1967 as part of the newly formed U.S. Department of Transportation (DOT). Congress made it responsible for investigating all civil aviation accidents and certain accidents in other modes of transportation, with the intent of identifying safety improvements to prevent future accidents. In 1974, Congress passed the Independent Safety Board Act of 1974 (in P.L. 93-633 ), making the NTSB completely independent of DOT. As an independent agency, the NTSB can carry out unbiased investigations and make recommendations regarding safety regulations and oversight practices of DOT without inherent conflicts of interest. The NTSB's main functions are determining the causes of accidents and recommending safety improvements that could prevent such accidents from recurring. Additionally, the NTSB provides assistance to victims' families in major airline and passenger rail disasters and serves as a board of appeals for certain transportation regulatory actions by the Federal Aviation Administration (FAA) and the U.S. Coast Guard. The agency has no authority to require implementation of its recommendations. It does not regulate or oversee safety practices in the transportation sector; those responsibilities are assigned to DOT; DOT modal agencies including FAA and the Federal Railroad Administration; and other federal and state agencies. The NTSB consists of a five-member board and a staff of approximately 420. About three-quarters of the staff are located at the NTSB's Washington, DC, headquarters. In addition, the NTSB maintains four regional offices in Ashburn, VA; Denver, CO; Federal Way, WA; and Anchorage, AK. The NTSB also has a training center in Ashburn, VA. The NTSB Reauthorization Act of 2006 ( P.L. 109-443 ) included a provision that requires the NTSB to maintain at least one full-time employee in every state located more than 1,000 miles from the nearest NTSB regional office to provide initial investigative response to accidents. This measure directly impacts the state of Hawaii, where the NTSB does not have a field office. Since passage of this legislation, the NTSB has maintained one aviation safety investigator in Hawaii. In recent years, NTSB regional staff have become more geographically dispersed, and are physically located in 25 states. The five Safety Board members, presidentially appointed with the advice and consent of the Senate, serve five-year terms and may continue to serve beyond their terms until replacement board members are appointed. Not more than three Safety Board members may be appointed from the same political party, and at least three of the members must be appointed on the basis of technical qualifications, professional standing, and knowledge of transportation safety issues. Investigative and support staff are organized under separate offices for each transportation mode, with the office of research and engineering supporting all of the modal offices. The NTSB also serves as a court of appeals for airmen and mariners who are subject to administrative actions by the FAA or the Coast Guard. Such cases are initially adjudicated by the NTSB's Office of Administrative Law Judges. The NTSB also has an Office of Safety Recommendations and Communications whose responsibilities include working with modal administrations and other recipients of NTSB safety recommendations to track correspondence and actions taken in response to those recommendations. The office also coordinates communications with Congress, transportation stakeholders, and the public regarding Board actions and transportation safety advocacy (see Figure 1 ). The NTSB investigates the following transportation-related accidents and safety issues: all accidents involving civil aircraft and public aircraft, other than military or intelligence agency aircraft, within the United States and its territories; selected highway and railroad grade crossing accidents; railroad accidents involving passenger trains, loss of life, or significant property damage; pipeline accidents involving significant property or environmental damage, or loss of life; in coordination with the Coast Guard, major marine casualties occurring on the navigable waters or territorial sea of the United States, or involving U.S.-flag vessels, except those involving only public (i.e., government-owned or -operated) vessels; and other selected catastrophic accidents or recurring problems involving transportation safety investigated at the Board's discretion. While the NTSB employs investigators and subject matter experts in a number of engineering and technical disciplines, it relies extensively on the expertise of manufacturers, transportation providers, and regulatory agencies connected with an accident to assist with investigations. It does so through what is known as the "party process," in which the NTSB investigator-in-charge designates parties to participate in an investigation. The parties then assign qualified technical personnel to assist the NTSB. A number of safeguards exist to prevent external entities from influencing NTSB findings and conclusions. First, while interested parties may provide technical expertise in the fact-finding phase of an investigation and may submit their own analyses for consideration by NTSB investigators, the NTSB bases its conclusions strictly on analysis and recommendations by NTSB staff. Formal procedures exist for parties to petition the NTSB to reconsider or modify its investigative findings after an investigation has been completed and the final report has been adopted. Other than the FAA in aviation cases, no party has a specific right to hold party status in an investigation; parties can be sanctioned or lose their party status if they do not fulfill assigned duties and comply with rules of conduct. Under provisions of the Government in the Sunshine Act ( P.L. 94-409 ), the Safety Board as a whole must meet in public on most matters pertaining to accident investigations. Board members and senior investigative staff must also provide financial disclosures, and are precluded from maintaining certain financial interests in transportation-related companies. Despite these safeguards, the potential for parties to exert their influence on the NTSB process still exists. Even if the NTSB was not swayed by outside efforts to influence an investigation, a public perception that the agency is not fully impartial could diminish its credibility. Striking a balance between allowing parties to the investigation to provide unique data and technical expertise that often they alone possess while preventing them from attempting to sway the investigative process is a sizable challenge. Moreover, during highly complex and contentious accident investigations, evaluating competing perspectives brought forth by various parties to the investigation can prove challenging for the NTSB, and can stretch out the length of time needed to complete an investigation. In accordance with international treaties and standard practices for aviation accident investigation set forth by the International Civil Aviation Organization (ICAO), the NTSB participates in investigations of foreign aviation accidents involving any U.S.-manufactured or -registered aircraft. On occasion, the NTSB may also lend its expertise to foreign investigations at the request of another country, even though the United States may have no vested interest or any specific right under international agreements to participate in the accident investigation process. In instances where the NTSB is asked to consult or actively participate in an overseas investigation, the NTSB may be reimbursed for associated costs from outside entities such as a foreign government. P.L. 109-443 included a provision designating such receipts, whether in the form of fees or reimbursements, as offsetting collections available until expended. Prior to this legislative change, only reimbursements related to activities of the NTSB Academy, such as tuition payments or classroom rental fees, were specifically credited as offsetting collections. In addition, the NTSB has recovered some costs associated with foreign aviation accident investigations through DOT's Safe Skies for Africa program. Between FY2012 and FY2015, its costs for participating in international investigations have ranged from just under $1 million to almost $2.4 million annually, of which between roughly $40,000 and $150,000 has been covered under the Safe Skies for Africa program. The NTSB has no direct authority to change transportation safety regulations and practices. Its principal means for effecting change in transportation safety is the issuance of safety recommendations to regulators, operators, and users of transportation systems. Since investigations of complex accidents may take several years, the NTSB routinely issues recommendations over the course of an investigation as needed safety improvements are identified. Since 1967, the NTSB has issued over 14,300 safety recommendations to more than 2,300 recipients across all modes of transportation. Historically, about 82% of NTSB recommendations have led to the implementation of safety improvements deemed acceptable by the Board. DOT agencies must provide a formal written response to each NTSB recommendation within 90 days of receipt, detailing how they intend to implement the recommendation in whole or in part, or explaining the reasons for not implementing the recommendation. There is no statutory requirement for agencies and organizations to adopt NTSB-issued safety recommendations. However, the NTSB often publicizes its recommendations and advocates for sought-after transportation safety improvements in order to build public support for their implementation. While most NTSB safety recommendations are eventually implemented, implementation may be prolonged due to lengthy rulemaking processes, as well as concerns about feasibility, costs, and benefits. The NTSB explicitly does not take benefit/cost considerations into account in developing its recommendations. Nor is it charged with weighing the cost of implementing a particular safety recommendation against other safety-related expenditures a transportation carrier or government agency might undertake. The NTSB highlights key safety recommendations on a list of "Most Wanted" safety improvements. Currently the list seeks actions to reduce fatigue-related accidents; improve rail transit safety oversight; promote the availability of collision avoidance technologies in highway vehicles; strengthen occupant protection in highway vehicles, passenger trains, and aircraft; minimize operator distractions that cause transportation accidents; prevent loss of control in flight in general aviation; promote completion of rail safety initiatives including positive train control and improved tank car design; end substance impairment in transportation; and require operators to be medically fit for duty. These "Most Wanted" transportation safety improvements typically encompass numerous specific recommendations requesting action from DOT and the states. Often, such action requires statutory and regulatory changes.