Final answer:
The name of the reference used to determine the initial response to a Hazardous Materials incident is the DOT Emergency Response Guide.
Step-by-step explanation:
The name of the reference used to determine the initial response to a Hazardous Materials (HazMat) incident is the DOT Emergency Response Guide. The DOT Emergency Response Guide provides first responders with guidance on how to respond to different types of hazardous materials incidents. It includes information on the potential hazards, proper response techniques, and safety precautions to be taken.