In emergency vehicle operation, which factor is NOT a condition justifying the use of lights and siren?

In the context of emergency vehicle operation, the primary purpose of using lights and siren is to alert other road users of the emergency vehicle's presence and to facilitate safe passage through traffic. The factors that typically justify the use of lights and siren include circumstances that indicate an immediate need to respond quickly, such as severe weather conditions that may hinder visibility or road safety, the severity of the crime or incident requiring urgent intervention, and the presence of pedestrians which can necessitate enhanced warnings to ensure safety.

However, fuel efficiency does not relate to the justification for emergency response methods. The vehicle's fuel efficiency is a factor concerned with operational costs and resource management, not with the urgency or necessity of the response. Therefore, it is not considered a condition that warrants the use of lights and siren in emergency situations.