Final answer:
A railroad tank car with 300 gallons of toluene is classified as a flammable substance, as toluene is a solvent with high flammability, regulated by the DOT and EPA.
Step-by-step explanation:
A railroad tank car containing 300 gallons of toluene is considered to be a flammable substance. Toluene is a clear, water-insoluble liquid with the typical smell of paint thinners, renowned for its solvent properties. It is categorized as a hazardous material, particularly due to its high flammability. When dealing with transportation and substance classifications, both the United States Department of Transportation (DOT) and the Environmental Protection Agency (EPA) regulations need to be considered. According to the DOT and EPA, toluene fits within the category of flammable liquids, which are materials that can pose a significant risk of fire at ambient temperatures.