Emergency vehicle equipment

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.

Passive visual warnings

The passive visual warnings are usually inherently linked to the design of the vehicle, and involve the use of high contrast patterns. Older vehicles are more likely to have their pattern painted on, whereas modern vehicles generally carry the retro-reflective designs which reflect light from car headlights or torches (and was invented by 3M). Popular patterns include 'checker board' (alternate coloured squares, sometimes called 'Battenburg markings'), chevrons (arrowheads - often pointed towards the front of the vehicle if on the side, or pointing vertically upwards on the rear) or stripes (along the side - these were the first type or retro-reflective device introduced, as the original 3M reflective material only came in tape form). In some countries, in addition to retro-reflective markings, the vehicles are now painted in a bright yellow or orange colour underneath, in order to maximise visual impact.

Another passive marking form is the name of the emergency service spelled out in reverse on the front of the vehicle (e.g. Ambulance or Fire). This enables drivers of other vehicles to more easily identify an approaching emergency vehicle in their rear view mirrors. The vehicle may also display the name of their owner or operator, and a telephone number which may be used to summon the vehicle.

Ambulances may also carry an emblem (either as part of the passive warning markings or not). Some ambulances may display a Red Cross, Red Crescent or Red Diamond (collective known as the Protective Symbols). These are symbols laid down by the Geneva Conventions, and all countries signatory to it agree to restrict their use to either (1) Military Ambulances or (2) the national Red Cross or Red Crescent society. Use by any other person, organisation or agency is in breach of international law. The protective symbols are designed to indicate to all people (especially combatants in the case of war) that the vehicle is neutral and is not to be fired upon (see Military ambulances), hence giving protection to the medics and their casualties, although this has not always been adhered to.

Many ambulances use the Star of Life, which indicates that the vehicle's operators can render their given level of care represented on the six pointed star.

Active visual warnings

The active visual warnings are usually in the form of flashing coloured lights (also known as 'beacons' or 'lightbars'). These flash in order to attract the attention of other road users as the emergency vehicle approaches, or to provide warning to motorists approaching a stopped vehicle in a dangerous position on the road (and if the emergency vehicle positions itself to deliberately move people away from an incident, this is called fend off). Common colours for emergency vehicle warning beacons are blue and red, and this varies by country (and sometimes by operator).

The lights can be made to flash via a range of techniques, dependent on the technology used, and the desired end effect. Types of beacon include:

• Light bars - A long but narrow 'strip' of lights on top of an emergency vehicle, which can be configured with almost infinite combinations of different lighting technologies from the list below. These are typically the main source of flashing light for the vehicle, and are used on overt marked emergency vehicles. They can also be divided into sections, with an array of functions (for instance front blue flashing lights, and rear red flashing lights, switched separately). Due to the nature of the wind resistance encountered by these large units, the majority must be fixed to the car permanently, although some units (usually smaller) are available with either magnetic or suction cup mountings which can be removed. The Light bar may also contain the Audible Warning devices. Some jurisdictions disallow the sale of lightbars to the general public (especially if mandated under state and/or federal law regardless of lens coloring which are not red and blue).
• Beacons - A simple lighting device, often found on smaller emergency vehicles, or unmarked cars, (where it is removable) and consists of a clear or transparent coloured casing surrounding a lamp and a revolving mirror. Some beacons consist of one or several lamps that revolve, instead of using a mirror. These were the original type of emergency vehicle lighting
• Alternating Vehicle Lights or Wig-wags - This causes the Full beam headlights, or Fog lights to flash in a pattern (usually alternating left-right-left, although it can be together, or in a random pattern), and can also be used at the rear of the vehicle on Brake, Fog or reversing lights to warn vehicles approaching from the rear.
• Grille lights - Flashing lights fitted on, into or behind the grille of the emergency vehicle, creating forward-facing flashing effects, designed to be seen in the rear view mirror of moving traffic in front of the vehicle. These can be fitted to both overt and covert emergency vehicles, by simply changing whether they are mounted internally or externally, or by varying the lens colour (so that they may look like fog lights on a covert vehicle)
• Dash Lights - These are forward-facing lights, like grille lights, but mounted on the dashboard of the emergency vehicle. They are more often found on covert vehicles, but may be found on some marked vehicles which are trying to increase visibility. In order to avoid dazzling the driver, they are normally fitted with 'shields' around the light which stop the light reflecting into the cab.
• Deck lights (or Parcel Shelf lights) - Rear-facing equivalents of the Dash Lights which are placed on the Parcel Shelf of the vehicle. These can be used in both overt and covert vehicles.

• Directional Warning Arrows or arrow sticks - A strip of lights (typically amber or yellow) which light up in sequence to direct traffic to the right, left, or around both sides of an emergency vehicle. They may be found mounted on the back of a lightbar, on a car's package shelf (shining out the rear window) or on some other conspicuous location on the rear of a vehicle.
• Information Matrix Signs - These special active visual warnings are used to convey words to vehicles approaching from behind the emergency vehicle and often carry messages such as "Police. Stop" or other relevant message. Some systems allow only preprogrammed messages, where others can be fully customised.

Many governments list specific requirements for emergency vehicle lighting. These requirements may address the colour, location and intensity/visibility of the lights, and whether they should flash or burn steadily. Laws also may regulate what vehicles may display these lights, and under what circumstances they may do so.

The warning lights may be of several types, which includes:

• Incandescent - These are 'traditional' light bulbs, and may be found in the 'beacon' type lights, and will also be found where the vehicle's own lighting is used (such as wig-wag). Bulbs may be Halogen or Xenon type. They may use a rotating mirror to make them flash, or are simply turned on and off.
• Strobe lights - These lights give a short flash, which has high brightness compared to an incandescent light. They are usually made to work in multiples (such as three rapid flashes consecutively) and are often used in patterns between sets, which increases their effectiveness.
• LED lights - These are more recent developments, using the 'Super Bright' LED technology, and are entering wide use as they are easy to fit (being only a few millimetres wide, rather than several centimetres for most strobes and incandescent lights). This makes them particularly suitable for covert use. Though currently much more expensive than other types of lamps, there are substantial benefits. They draw much less electric current than other types of lamps which is a valuable reduction in electrical load on these vehicles' over-stressed electrical systems. They are much more resistant to vibration and have much longer service lives. They also present very saturated colors and so enhance visibility during daylight hours.