This response to your letter regarding training requirements under the Hazardous Materials Regulations (HMR; 49 CFR Parts 171-180) applicable to a truck driver who is responsible for loading and unloading hazardous materials from a cargo tank motor vehicle with the power unit attached. Specifically, you are unclear on whether the Occupational Safety and Health Administration (OSHA) or the Pipeline and Hazardous Materials Safety Administration (PHMSA) has jurisdiction over the transportation of hazardous materials in commerce. In addition, you ask if the HMR require: