Which organization regulates commercial operations for large vehicles and buses?

The Federal Motor Carrier Safety Administration (FMCSA) is the organization responsible for regulating commercial operations for large vehicles and buses. The FMCSA focuses specifically on ensuring safety within the trucking industry, which includes regulations for drivers, vehicles, and the transportation of goods and passengers. This includes setting standards for licensing, hours of service, and vehicle maintenance to ensure a safe transportation environment.

The other options, while related to transportation and vehicle safety, serve different purposes. The Department of Transportation (DOT) oversees all aspects of transportation in the United States, but it is the FMCSA that specifically targets commercial vehicle safety regulations. The National Highway Traffic Safety Administration (NHTSA) is more focused on reducing road traffic accidents and improving vehicle safety standards, but it does not regulate commercial operations directly. The Environmental Protection Agency (EPA) deals with environmental protection, including emissions regulations, but it does not regulate the operational aspects of commercial vehicles in the same way FMCSA does. Thus, the FMCSA is the correct answer as it directly oversees the commercial operations of large vehicles and buses.