guidance concerning the Federal Motor Carrier Safety Regulations. List of FMCSA Service Centers List of FMCSA Field Offices Main programs Compliance, Safety, Accountability (CSA) Compliance, Safety, Accountability (CSA) is described by FMCSA as its "data-driven safety compliance and enforcement program designed to improve safety and prevent commercial motor vehicle crashes, injuries, and fatalities". This program oversees carriers’ safety performance through roadside inspections and crash investigations, issuing violations when instances of noncompliance with safety regulations are uncovered. The Agency’s safety investigation team and state law enforcement partners are small compared to the millions of CMV companies and commercial driver license (CDL) holders nationwide. A key component of the CSA program – known as the Safety Measurement System (SMS) – relies on data analysis to identify non-compliant and unsafe companies to prioritize them for enforcement interventions. While the methodology for calculating SMS safety scores has evolved over time in response to suggestions from stakeholders, the program has proven effective at identifying unsafe, high-risk carriers. FMCSA is expected to publicly release additional changes to SMS designed to strengthen the Agency’s ability to identify companies for investigation before they are involved in a crash. The program's future remains in doubt as it has been the subject of heavy criticism from the DOT's own Inspector General, the Government Accountability Office, and Congress itself in the FAST Act. That Act requires the National Research Council of the National Academies of Science (NAS) to conduct a thorough study of the Compliance, Safety, Accountability (CSA) program, specifically the Safety Measurement System (SMS). Hours of Service (HOS) and Driver Restart Study In July 2013, FMCSA updated HOS regulation to help reduce the incidence of CMV driver fatigue on the nation’s roadways. The final rule required truck drivers who use the “34-hour restart” provision to maximize their weekly work hours to limit the restart to once a week and to include in the restart period at least two nights off duty from 1:00 to 5:00 a.m., when one’s 24-hour body clock supposedly needs and benefits from sleep the most. In December 2014, Congress passed the FAST Act, which suspended the new 34-hour restart provision in the HOS rule and instructed FMCSA to study its effectiveness. In 2015, FMCSA selected Virginia Tech Transportation Institute (VTTI) to conduct the largest naturalistic study of its kind that the Agency had ever undertaken. FMCSA anticipated releasing the findings in 2017. National Registry Implemented in