An ambulance is a medically equipped vehicle which transports patients to treatment facilities, such as hospitals.^[1] In some instances, out-of-hospital medical care is provided to the patient.

Ambulances are used to respond to medical emergencies by emergency medical services. For this purpose, they are generally equipped with flashing warning lights and sirens. They can rapidly transport paramedics and other first responders to the scene, carry equipment for administering emergency care and transport patients to hospital or other definitive care. Most ambulances use a design based on vans or pick-up trucks. Others take the form of motorcycles, cars, buses, aircraft and boats (see below: Vehicle types). In Japan, This car operated by Ministry of Internal Affairs and Communications

Generally, vehicles count as an ambulance if they can transport patients. However, it varies by jurisdiction as to whether a non-emergency patient transport vehicle (also called an ambulette) is counted as an ambulance. These vehicles are not usually (although there are exceptions) equipped with life-support equipment, and are usually crewed by staff with fewer qualifications than the crew of emergency ambulances. Conversely, EMS agencies may also have emergency response vehicles that cannot transport patients.^[2] These are known by names such as nontransporting EMS vehicles, fly-cars or response vehicles.

The term ambulance comes from the Latin word "ambulare" as meaning "to walk or move about"^[3] which is a reference to early medical care where patients were moved by lifting or wheeling. The word originally meant a moving hospital, which follows an army in its movements.^[4] Ambulances (Ambulancias in Spanish) were first used for emergency transport in 1487 by the Spanish forces during the siege of Málaga by the Catholic Monarchs against the Emirate of Granada. During the American Civil War vehicles for conveying the wounded off the field of battle were called ambulance wagons.^[5] Field hospitals were still called ambulances during the Franco-Prussian War^[6] of 1870 and in the Serbo-Turkish war of 1876^[7] even though the wagons were first referred to as ambulances about 1854 during the Crimean War.^[8]

The history of the ambulance begins in ancient times, with the use of carts to transport incurable patients by force. Ambulances were first used for emergency transport in 1487 by the Spanish, and civilian variants were put into operation during the 1830s.^[9] Advances in technology throughout the 19th and 20th centuries led to the modern self-powered ambulances.

Ambulances can be grouped into types depending on whether or not they transport patients, and under what conditions. In some cases, ambulances may fulfil more than one function (such as combining emergency ambulance care with patient transport

In the US, there are four types of ambulances. There are Type I, Type II, Type III and Type IV. Type I is based upon a heavy truck chassis with a custom rear compartment that is often referred to as a "box." Type I ambulances are primarily used for Advanced Life Support(ALS), also referred to as Mobile Intensive Care Unit(MICU) in some jurisdictions, and rescue work. A Type II ambulance is based on a commercial heavy-duty van with few modifications except for a raised roof and a secondary air conditioning unit for the rear of the vehicle. These types of ambulances are primarily used for Basic Life Support(BLS) and transfer of patients but it is not uncommon to find them used for advanced life support and rescue. Type III is a van chassis but with a custom-made rear compartment and has the same uses as Type I ambulances. Type IV is for smaller ad hoc patient transfer that use smaller utility vehicles in which passenger vehicles and trucks would have difficulty in traversing, such as large industrial complexes, commercial venues, and special events with large crowds; they generally do not fall under Federal Regulations.^[13][14][15]

Ambulances can be based on many types of vehicle although emergency and disaster conditions may lead to other vehicles serving as makeshift ambulances:

Ambulance design must take into account local conditions and infrastructure. Maintained roads are necessary for road going ambulances to arrive on scene and then transport the patient to a hospital, though in rugged areas four-wheel drive or all-terrain vehicles can be used. Fuel must be available and service facilities are necessary to maintain the vehicle.

Methods of summoning (e.g. telephone) and dispatching ambulances usually rely on electronic equipment, which itself often relies on an intact power grid. Similarly, modern ambulances are equipped with two-way radios^[35] or cellular telephones to enable them to contact hospitals, either to notify the appropriate hospital of the ambulance's pending arrival, or, in cases where physicians do not form part of the ambulance's crew, to confer with a physician for medical oversight.^[36]

Ambulances often have two manufacturers. The first is frequently a manufacturer of light or medium trucks or full-size vans (or in some places, cars) such as Mercedes-Benz, Nissan, Toyota, or Ford.^[37] The second manufacturer (known as second stage manufacturer) purchases the vehicle (which is sometimes purchased incomplete, having no body or interior behind the driver's seat) and turns it into an ambulance by adding bodywork, emergency vehicle equipment, and interior fittings. This is done by one of two methods – either coachbuilding, where the modifications are started from scratch and built on to the vehicle, or using a modular system, where a pre-built 'box' is put on to the empty chassis of the ambulance, and then finished off.

Modern ambulances are typically powered by internal combustion engines, which can be powered by any conventional fuel, including diesel, gasoline or liquefied petroleum gas,^[38][39] depending on the preference of the operator and the availability of different options. Colder regions often use gasoline-powered engines, as diesels can be difficult to start when they are cold. Warmer regions may favor diesel engines, as they are thought to be more efficient and more durable. Diesel power is sometimes chosen due to safety concerns, after a series of fires involving gasoline-powered ambulances during the 1980s. These fires were ultimately attributed in part to gasoline's higher volatility in comparison to diesel fuel.^[40][41] The type of engine may be determined by the manufacturer: in the past two decades, Ford^[42][43][44] would only sell vehicles for ambulance conversion if they are diesel-powered. Beginning in 2010, Ford will sell its ambulance chassis with a gasoline engine in order to meet emissions requirements.^[45]

Many regions have prescribed standards which ambulances should, or must, meet in order to be used for their role. These standards may have different levels which reflect the type of patient which the ambulance is expected to transport (for instance specifying a different standard for routine patient transport than high dependency), or may base standards on the size of vehicle.

For instance, in Europe, the European Committee for Standardization publishes the standard CEN 1789, which specifies minimum compliance levels across the build of ambulance, including crash resistance, equipment levels, and exterior marking. In the United States, standards for ambulance design have existed since 1976, where the standard is published by the General Services Administration and known as KKK-1822-A.^[46] This standard has been revised several times, and is currently in version 'F' change #10, known as KKK-A-1822F, although not all states have adopted this version. The National Fire Protection Association has also published a design standard, NFPA 1917, which some administrations are considering switching to if KKK-A-1822F is withdrawn.^[47]. The Commission on Accreditation of Ambulance Services (CAAS) has published its Ground Vehicle Standard for Ambulances effective July 2016. This standard is similar to the KKK-A-1822F and NFPA 1917-2016 specifications.

The move towards standardisation is now reaching countries without a history of prescriptive codes, such as India, which approved its first national standard for ambulance construction in 2013.^[48]

Ambulances, like other emergency vehicles, are required to operate in most weather conditions, including those during which civilian drivers often elect to stay off the road. Also, the ambulance crew's responsibilities to their patient often preclude their use of safety devices such as seat belts. Research has shown that ambulances are more likely to be involved in motor vehicle collisions resulting in injury or death than either fire trucks or police cars. Unrestrained occupants, particularly those riding in the patient-care compartment, are particularly vulnerable.^[49] When compared to civilian vehicles of similar size, one study found that on a per-accident basis, ambulance collisions tend to involve more people, and result in more injuries.^[50] An 11-year retrospective study concluded in 2001 found that although most fatal ambulance crashes in the United States occurred during emergency runs, they typically occurred on improved, straight, dry roads, during clear weather.^[51] Furthermore, paramedics are also at risk in ambulances while helping patients, as 27 paramedics died during ambulance trips in the US between 1991 and 2006.^[52]

In addition to the equipment directly used for the treatment of patients, ambulances may be fitted with a range of additional equipment which is used in order to facilitate patient care. This could include:

In parts of the world which lack a high level of infrastructure, ambulances are designed to meet local conditions, being built using intermediate technology. Ambulances can also be trailers, which are pulled by bicycles, motorcycles, tractors, or animals. Animal-powered ambulances can be particularly useful in regions that are subject to flooding. Motorcycles fitted with sidecars (or motorcycle ambulances) are also used, though they are subject to some of the same limitations as more traditional over-the-road ambulances. The level of care provided by these ambulances varies between merely providing transport to a medical clinic to providing on-scene and continuing care during transport.^[17]

The design of intermediate technology ambulances must take into account not only the operation and maintenance of the ambulance, but its construction as well. The robustness of the design becomes more important, as does the nature of the skills required to properly operate the vehicle. Cost-effectiveness can be a high priority.^[18][58]

Emergency ambulances are highly likely to be involved in hazardous situations, including incidents such as a road traffic collision, as these emergencies create people who are likely to be in need of treatment. They are required to gain access to patients 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 yield sign ('give way'),^[59] or be permitted to break the speed limit.^[60] Generally, the priority of the response to the call will be assigned by the dispatcher, but the priority of the return will be decided by the ambulance crew based on the severity of the patient's illness or injury. Patients in significant danger to life and limb (as determined by triage) require urgent treatment by advanced medical personnel,^[61] and because of this need, emergency ambulances are often fitted with passive and active visual and/or audible warnings to alert road users.

The passive visual warnings are usually part of the design of the vehicle, and involve the use of high contrast patterns. Older ambulances (and those in developing countries) are more likely to have their pattern painted on, whereas modern ambulances generally carry retro-reflective designs, which reflects light from car headlights or torches. Popular patterns include 'checker board' (alternate coloured squares, sometimes called 'Battenburg', named after a type of cake), 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 of retro-reflective device introduced, as the original reflective material, invented by 3M, only came in tape form). In addition to retro-reflective markings, some services now have the vehicles painted in a bright (sometimes fluorescent) yellow or orange for maximum visual impact, though classic white or red are also common. Fire department-operated ambulances are often painted red to match the fire apparatuses.

Another passive marking form is the word ambulance (or local language variant) spelled out in reverse on the front of the vehicle. This enables drivers of other vehicles to more easily identify an approaching ambulance in their rear view mirrors. Ambulances may display the name of their owner or operator, and an emergency telephone number for the ambulance service.

Ambulances may also carry an emblem (either as part of the passive warning markings or not), such as a Red Cross, Red Crescent or Red Crystal (collective known as the Protective Symbols). These are symbols laid down by the Geneva Convention, 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, organization 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, hence giving protection to the medics and their casualties, although this has not always been adhered to. In Israel, Magen David Adom, the Red Cross member organization use a red Star of David, but this does not have recognition beyond Israeli borders, where they must use the Red Crystal.

The Star of Life is widely used, and was originally designed and governed by the U.S. National Highway Traffic Safety Administration,^[62] because the Red Cross symbol is legally protected by both National^[63] and international^[64][65] law

Ambulance services that have historical origins such as the Order of St John, the Order of Malta Ambulance Corps^[66] and Malteser International^[67] often use the Maltese cross to identify their ambulances. This is especially important in countries such as Australia, where St. John Ambulance operate one state and one territory ambulance service, and all of Australia's other ambulance services use variations on a red Maltese cross.^{[68][69][70][71]}

Fire service operated ambulances may display the Cross of St. Florian (often incorrectly called a Maltese cross) as this cross is frequently used as a fire department logo (St. Florian being the patron saint of firefighters).^[72]

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.

See also Emergency vehicle equipment.

In addition to visual warnings, ambulances can be fitted with audible warnings, sometimes known as sirens, which can alert people and vehicles to the presence of an ambulance before they can be seen. The first audible warnings were mechanical bells, mounted to either the front or roof of the ambulance. Most modern ambulances are now fitted with electronic sirens, producing a range of different noises which ambulance operators can use to attract more attention to themselves, particularly when proceeding through an intersection or in heavy traffic.^[73]

The speakers for modern sirens can be integral to the lightbar, or they may be hidden in or flush to the grill to reduce noise inside the ambulance that may interfere with patient care and radio communications. Ambulances can additionally be fitted with airhorn audible warnings to augment the effectiveness of the siren system, or may be fitted with extremely loud two-tone airhorns as their primary siren.

A recent development is the use of the RDS system of car radios. The ambulance is fitted with a short range FM transmitter, set to RDS code 31, which interrupts the radio of all cars within range, in the manner of a traffic broadcast, but in such a way that the user of the receiving radio is unable to opt out of the message (as with traffic broadcasts).^[74] This feature is built into every RDS radio for use in national emergency broadcast systems, but short range units on emergency vehicles can prove an effective means of alerting traffic to their presence. It is, however, unlikely that this system could replace audible warnings, as it is unable to alert pedestrians, those not using a compatible radio or even have it turned off.^[75]

The cost of an ambulance ride may be paid for from several sources, and this will depend on the type of service being provided, by whom, and possibly who to.

There are differing levels of qualification that the ambulance crew may hold, from holding no formal qualification to having a fully qualified doctor on board. Most ambulance services require at least two crew members to be on every ambulance (one to drive, and one to attend the patient). It may be the case that only the attendant need be qualified, and the driver might have no medical training. In some locations, an advanced life support ambulance may be crewed by one paramedic and one EMT-Basic.

Common ambulance crew qualifications are:

Military ambulances have historically included vehicles based on civilian designs and at times also included armored, but unarmed, vehicles ambulances based upon armoured personnel carriers (APCs). In the Second World War vehicles such as the Hanomag Sd Kfz 251 halftrack were pressed into service as ad hoc ambulances, and in more recent times purpose built AFVs such as the U.S. M1133 Medical Evacuation Vehicle serve the exclusive purpose of armored medical vehicles. Civilian based designs may be painted in appropriate colours, depending on the operational requirements (i.e. camouflage for field use, white for United Nations peacekeeping, etc.). For example, the British Royal Army Medical Corps has a fleet of white ambulances, based on production trucks. Military helicopters have also served both as ad hoc and purpose-built air ambulances, since they are extremely useful for MEDEVAC.^[89] In terms of equipment, military ambulances are barebones, often being nothing more than a box on wheels with racks to place manual stretchers, though for the operational conditions and level of care involved this is usually sufficient.

Since laws of war demand ambulances be marked with one of the Emblems of the Red Cross not to mount offensive weapons, military ambulances are often unarmed.^[90] It is a generally accepted practice in most countries to classify the personnel attached to military vehicles marked as ambulances as non-combatants; however, this application does not always exempt medical personnel from catching enemy fire—accidental or deliberate. As a result, medics and other medical personnel attached to military ambulances are usually put through basic military training,^[91] on the assumption that they may have to use a weapon. The laws of war do allow non-combatant military personnel to carry individual weapons for protecting themselves and casualties. However, not all militaries exercise this right to their personnel.

Recently, the Israeli Defense Forces has modified a number of its Merkava main battle tanks with ambulance features in order to allow rescue operations to take place under heavy fire in urban warfare.^[92] The modifications were made following a failed rescue attempt in which Palestinian gunmen killed two soldiers who were providing aid for a Palestinian woman in Rafah.^[93] Since M-113 armored personnel carriers and regular up-armored ambulances are not sufficiently protected against anti-tank weapons and improvised explosive devices,^[94] it was decided to use the heavily armored Merkava tank. Its rear door enables the evacuation of critically wounded soldiers. Israel did not remove the Merkava's weaponry, claiming that weapons were more effective protection than emblems since Palestinian militants would disregard any symbols of protection and fire at ambulances anyway. For use as ground ambulances and treatment & evacuation vehicles, the United States military currently employs the M113, the M577, the M1133 Stryker Medical Evacuation Vehicle (MEV), and the RG-33 Heavily Armored Ground Ambulance (HAGA) as treatment and evacuation vehicles, with contracts to incorporate the newly designed M2A0 Armored Medical Evacuation Vehicle (AMEV), a variant of the M2 Bradley Fighting Vehicle (formerly known as the ATTV).^[95][96][97]

Some navies operate ocean-going hospital ships to lend medical assistance in high casualty situations like wars or natural disasters.^[28] These hospital ships fulfill the criteria of an ambulance (transporting the sick or injured), although the capabilities of a hospital ship are more on par with a Mobile Army Surgical Hospital. In line with the laws of war, these ships can display a prominent Red Cross or Red Crescent to confer protection under the appropriate Geneva convention. However, this designation has not always protected hospital ships from enemy fire.^[98]

When an ambulance is retired, it may be donated or sold to another EMS provider.^[99][100] Alternately, it may be adapted into a storage and transport vehicle for crime scene identification equipment, a command post at community events, or support vehicle, such as a logistics unit.^[101] Others are refurbished and resold,^[102] or may just have their emergency equipment removed to be sold to private businesses or individuals, who then can use them as small recreational vehicles. They may also have a perfectly serviceable body or vehicle (or both) separated from the other and reused.

Toronto City Council has begun a "Caravan of Hope" project to provide retired Toronto ambulances a second life by donating them to the people of El Salvador. Since laws in Ontario require ambulances to be retired after just four and a half years in service, the City of Toronto decommissions and auctions 28 ambulances each year.^[103]