Visual Warning Devices
Emergency vehicles of any kind (fire truck, ambulance, police car) are highly likely to be involved in hazardous situations, including relatively common incidents such as a road traffic collision. They are also required to gain access to incidents as quickly as possible, and in many countries, are given dispensation from obeying certain traffic laws; for instance, they may be able to treat a red traffic light or stop sign as a give way, or be permitted to break the speed limit. However, emergency vehicles usually are not able to treat a railroad crossing as a give way, because a train cannot be warned in time to stop before the crossing to let the vehicle through. Hence, one of the few things emergency vehicles must yield to are heavy freight and passenger trains.
For these reasons, emergency vehicles in many countries worldwide, are fitted with visual warnings to alert members of the public (and in particular, other motorists and road users), either as they approach the vehicle, or it approaches them. Visual warnings can be of two types - passive warning or active warning.
Read more about this topic: Emergency Vehicle Equipment
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