When approaching a vehicle with flashing hazard lights, decreasing your speed and proceeding with caution is the appropriate action to take. The flashing hazard lights indicate that the vehicle is experiencing a problem or has stopped in a potentially dangerous situation. By slowing down, you allow yourself adequate time to assess the situation and respond safely.
Proceeding with caution ensures that you stay alert to any unexpected movements from the disabled vehicle or any pedestrians that may be nearby. This helps prevent accidents and protects both the occupants of the stopped vehicle and other road users.
Other options, such as speeding up to pass quickly or ignoring the hazard unless directed, present risks of failing to recognize and respond to a potentially hazardous situation. Stopping completely regardless of conditions may create additional hazards, especially if you are on a busy road where sudden stops can lead to rear-end collisions. Thus, decreasing speed and exercising caution is not only the safest course of action but also aligns with best driving practices when approaching a vehicle with flashing hazard lights.