Ambulance
Active visual warnings

The active visual warnings are usually in the form of flashing lights. These flash in order to attract the attention of other road users as the ambulance approaches, or to provide warning to motorists approaching a stopped ambulance in a dangerous position on the road. Common colours for ambulance warning beacons are blue, red, amber, and white (clear). However the colours may vary by country and sometimes by operator.

There are several technologies in use to achieve the flashing effect. These include flashing a light bulb or LED, flashing or rotating halogen, and strobe lights, which are usually brighter than incandescent lights. Each of these can be programmed to flash singly or in groups, and can be programmed to flash in patterns (such as a left -> right pattern for use when the ambulance is parked on the left hand side of the road, indicating to other road users that they should move to the right (away from the ambulance)). Incandescent and LED lights may also be programmed to burn steadily, without flashing, which is required in some provinces.

Emergency lights may simply be mounted directly on the body, or may be housed in special fittings, such as in a lightbar or in special flush-mount designs (as seen on the Danish ambulance to the right), or may be hidden in a host light (such as a headlamp) by drilling a hole in the host light's reflector and inserting the emergency light. These hidden lights may not be apparent until they are activated. Additionally, some of the standard lights fitted to an ambulance (e.g. headlamps, tail lamps) may be programmed to flash. Flashing headlights (typically the high beams, flashed alternately) are known as a wig-wag. Additional white lights may be placed strategically around the vehicle to illuminate the area around it when it is dark, almost always at the rear for loading and unloading stretchers and often at the sides as well. In areas very far North or South where there are times of year with long periods of darkness, additional driving lights at the front are often fitted as well to increase visibility for the driver.

In order to increase safety, it is best practice to have 360° coverage with the active warnings, improving the chance of the vehicle being seen from all sides. In some countries, such as the United States, this may be mandatory. The roof, front grille, sides and rear of the body, and front fenders are common places to mount emergency lights. A certain balance must be made when deciding on the number and location of lights: too few and the ambulance may not be noticed easily, too many and it becomes a massive distraction for other road users more than it is already, increasing the risk of local accidents.
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