When is it preferable to use lights only, without sirens, on an emergency vehicle?

Using lights only, without sirens, is preferable in high pedestrian traffic areas primarily to minimize noise and potential panic among pedestrians. The activation of sirens can create a sense of urgency and alarm, which may lead to confusion or a chaotic response from individuals in the vicinity. This is particularly important in dense urban environments where sudden loud noises can startle people and disrupt their activities, potentially creating unsafe situations.

In these areas, the visual presence of emergency lights is often sufficient to alert drivers and pedestrians to the vehicle's approach, allowing them to yield the right of way without the added stress of sirens. This approach helps maintain a safer environment for both the emergency responders and the public. Additionally, operating with lights only can contribute to a more controlled and calm response in communities that are not experiencing a high level of threat.