Non-priority vehicles can use acoustic signals in emergency situations to alert other road users of their presence. This is important to prevent possible accidents and to warn other drivers that they need to pass due to an urgent service, such as taking a seriously injured person to the hospital.

Acoustic signals are sounds used to alert other drivers of the presence of a vehicle, and their use is permitted in specific situations, such as avoiding accidents or when performing a priority service. Although priority vehicles, such as ambulances and police cars, have specific lights and sirens for these cases, non-priority vehicles can also use acoustic signals to ensure that other drivers and pedestrians yield the right of way in emergency situations.

Therefore, the correct answer is that they can indeed use acoustic signals to alert others of their presence on the road.