What is the primary safety measure for vehicles carrying explosives?

Answer: C — Displaying a red flag of a stipulated size

Displaying a red flag of a stipulated size is the primary safety measure for vehicles carrying explosives because it serves as a visual signal to other drivers and pedestrians about the special hazards associated with the cargo. The red flag is a clear indication that the vehicle is transporting potentially dangerous materials, alerting others to exercise caution and maintain a safe distance. This is a critical safety protocol that helps prevent accidents and ensures that other road users are aware of the risks involved when approaching such vehicles. The other measures listed, while they may contribute to overall vehicle safety, do not specifically address the unique hazards of transporting explosives. Using advanced braking systems or additional mirrors can enhance general road safety, but they do not communicate the presence of hazardous materials. Similarly, painting the vehicle a specific color does not provide the immediate, visible warning that a flagged indicator does. Thus, the correct answer highlights the importance of communication regarding safety risks when dealing with dangerous goods.