**Priority vehicles**, such as ambulances, police cars, and fire trucks, are equipped with **blue light signals** and **acoustic signals** (sirens) to indicate that they are on an emergency service. These signals help alert other drivers and pedestrians of their presence and need for passage.

- **Light signals**: These are blue lights used to indicate that the vehicle is on an emergency service.
- **Acoustic signals**: Sounds used to warn other drivers, especially in situations where it is necessary to avoid an accident or when the vehicle needs to pass quickly.


Vehicles on emergency service have **right of way** on all roads, and other users must yield to them. However, it is important that these vehicles ensure their passage does not pose a **danger** to other road users.

- **Use of signals**: Although it is common for them to use both signals (light and acoustic) simultaneously, they may choose to use only the light signal if they consider that using the siren is not necessary and does not endanger others.

Therefore, it is correct for priority vehicles to use only the light signal **as long as it does not pose a danger to other users**.