Transportation workers who “blow the whistle” on prohibited practices can help ensure that their employers comply with federal laws. Within the Department of Labor, OSHA investigates whistleblower claims, filed by transportation employees who believe their employers have retaliated against them for reporting unlawful practices. The Moving Ahead for Progress in the 21st Century Act (MAP-21), required OSHA to establish protections for auto industry employees and required GAO to review OSHA’s efforts and transportation-related whistleblower claims. GAO examined (1) steps OSHA has taken to include auto industry employees in its whistleblower program and the extent to which OSHA collaborated with DOT components to address potential safety violations, and (2) the number of transportation-related whistleblower claims in the last 6 years and stakeholder-identified factors that may affect those numbers. GAO compared agency documents against key practices for collaboration, and interviewed federal agency officials and stakeholders representing transportation modes covered by these statutes to identify factors that may affect the number of whistleblower claims reported by OSHA.