Final answer:
In emergencies with no time to determine blood type, O negative blood is used for transfusion because it's a universal donor type and compatible with all recipients.
Step-by-step explanation:
Following a motor vehicle accident, when a patient is brought into the emergency department with multiple traumatic injuries requiring immediate blood transfusion, and there's no time to determine the patient's blood type, the type of blood transfused is typically O negative. This is because O negative blood is considered the universal donor type, which means it can be accepted by individuals of any blood type without causing an adverse reaction. The urgent need to control severe bleeding and stabilize the patient's condition makes the immediate availability and compatibility of O negative blood critical.