A car accident is a road traffic incident which usually involves one road vehicle colliding with, either another vehicle, another road user, or a stationary roadside object, and which may result in injury or property damage, or possibly death.

Terminology

Phrases used to describe accidents include: auto accident, car crash, car smash, car wreck, fender bender, motor vehicle accident (MVA), personal injury collision (PIC), road accident, road traffic accident (RTA), road traffic collision (RTC), road traffic incident (RTI), smash-up and traffic collision, "failure to communicate".

As the factors involved in collisions have become better understood, some organisations have begun to avoid the term "accident," as the word can suggest an unpredictable, unpreventable event. Although these events are rare in terms of the number of vehicles and drivers on the road, addressing the contributing factors can reduce the likelihood of collisions. For example, proper signing can decrease driver error and thereby reduce crash frequency by a third or more ^[1]. That is why these organisations prefer the term "crash," "collision," or some other term.

However, treating these incidents as anything other than "accidents" has been criticised for holding back safety improvements, because a culture of blame may discourage the involved parties from fully disclosing the facts, and thus frustrate attempts to address the real root causes.^[2]

 Background

Road crashes, causing death, injury, and damage have always happened since animals were domesticated. History tells of many notable historic personalities who were the victim of such incidents. Louis IV of France died in 954 after falling from his horse, as did at least two kings of England: William I (William the Conqueror) in 1087 and William III in 1702. Handel was seriously injured in a carriage crash in 1752.^[3]

The British road engineer J. J. Leeming, compared the statistics for fatality rates in Great Britain, for transport-related incidents both before and after the introduction of the motor vehicle, for journeys, including those by water, which would now be undertaken by motor vehicle:^[4] For the period 1863–1870 there were: 470 fatalities per million of population (76 on railways, 143 on roads, 251 on water); for the period 1891–1900 the corresponding figures were: 348 (63, 107, 178); for the period 1931–1938: 403 (22, 311, 70) and for the year 1963: 325 (10, 278, 37).^[4] Leeming concluded that the data showed that "travel accidents may even have been more frequent a century ago than they are now, at least for men.

Irish scientist Mary Ward died on 31 August 1869 when she fell out of her cousins' steam car and was run over. She is believed to have been the world's first motor vehicle accident victim.

A truck crash.

In the United States the calculable costs of motor-vehicle crashes are wage and productivity losses, medical expenses, motor vehicle damage, employers’ uninsured costs, and administrative expenses. (See the definitions for a description of what is included in each component.) The costs of all these items for each death (not each fatal crash), injury (not each injury crash), and property damage crash was: Average Economic Cost per Death, Injury, or Crash, 2006: Nonfatal; Disabling Injury; $55,000; Property Damage Crash (including nondisabling injuries) $8,200; Death; $1,210,000; Expressed on a per death basis, the cost of all motor vehicle crashes—i.e. fatal, nonfatal injury, and property damage—was $5,800,000. This includes the cost of one death, 197 property damage crashes (including minor injuries, 54 nonfatal disabling injuries). This average may be used to estimate the motor vehicle crash costs for a state provided that there are at least 10 deaths and only one or two occurred in each fatal crash. If fewer than 10 deaths, estimate the costs of deaths, nonfatal disabling injuries, and property damage crashes separately.

Defined in sections 2.3.4 through 2.3.6 of the Manual on Classification of Motor Vehicle Traffic Accidents (7th Edition) ANSI Standard D16.1-2007 are defined by severity motor vehicle injuries Estimates are given here of the costs by severity of injuries. http://www2.nsc.org/lrs/statinfo/estcost.htm

Road incidents result in the deaths of an estimated 1.2 million people worldwide each year, and injure about forty times this number (WHO, 2004).

 Contributing factors

See also: Road-traffic safety

Many jurisdictions require the collection and reporting of road traffic incident statistics. Such data enables figures for deaths, personal injuries, and possibly property damage to be produced, and correlated against a range of circumstances. Analysis of this data may allow incident clusters and incident causes to be identified.

Emergency responders at an accident in Colorado Springs, Colorado.

An early study by J. J. Leeming, a British road engineer, compared the circumstances around road deaths as reported in various American states (before the widespread introduction of 55 mph speed limits and drink-driving laws):^[4]

'They took into account thirty factors which it was thought might affect the death rate. Among these were included the annual consumption of wine, of spirits and of malt beverages — taken individually — the amount spent on road maintenance, the minimum temperature, certain of the legal measures such as the amount spent on police, the number of police per 100,000 inhabitants, the follow-up programme on dangerous drivers, the quality of driver testing, and so on. The thirty factors were finally reduced to six on elimination of those which were found to have small or negligible effect. The final six were:

• (a) The percentage of the total state highway mileage that is rural.
• (b) The percent increase in motor vehicle registration.
• (c) The extent of motor vehicle inspection.
• (d) The percentage of state-administered highway that is surfaced.
• (e) The average yearly minimum temperature.
• (f) The income per capita.

'These are placed in descending order of importance. These six accounted for 70% of the variations in the rate.'

A 1985 study by K. Rumar, using British and American crash reports as data, found that 57% of crashes were due solely to driver factors, 27% to combined roadway and driver factors, 6% to combined vehicle and driver factors, 3% solely to roadway factors, 3% to combined roadway, driver, and vehicle factors, 2% solely to vehicle factors and 1% to combined roadway and vehicle factors.^[5]

Driver behaviour

A Honda Accord after colliding with a building.

A 1985 report based on British and American crash data, found that driver error, intoxication and other human factors contribute wholly or partially to about 93% of crashes.^[5]

An RAC survey of British drivers found that most considered themselves to be "good" drivers, but that most others were not. Nearly all drivers who had had an accident did not believe themselves to be to blame.^[6] One survey of drivers reported that they thought the key elements of good driving were:^[7]

• controlling a car including a good awareness of the car's size and capabilities
• reading and reacting to road conditions, weather, road signs and the environment
• alertness, reading and anticipating the behaviour of other drivers.

Although proficiency in these skills is taught and tested as part of the driving exam, a 'good' driver can still be at a high risk of accidents because:

"the feeling of being confident in more and more challenging situations is experienced as evidence of driving ability, and that 'proven' ability reinforces the feelings of confidence. Confidence feeds itself and grows unchecked until something happens – a near-miss or an accident".^[7]

Accompanying changes to road designs have been wide-scale adoptions of rules of the road alongside law enforcement policies that included drink-driving laws, setting of speed limits, and speed enforcement systems such as speed cameras. Some countries' driving tests have been expanded to test a new driver's behaviour during emergencies, and their hazard perception.

There are demographic differences in accident rates. For example, although young people tend to have good reaction times, disproportionately more young male drivers feature in accidents,^[8] with researchers observing that many exhibit behaviours and attitudes to risk that can place them in more hazardous situations than other road users.^[7] This gets reflected by actuaries when they set insurance rates for different age groups, partly based on their age, sex, and choice of vehicle. Older drivers with slower reactions would be expected to be involved in more accidents, but this has not been the case as they tend to drive less and, apparently, more cautiously.^[9]

Toyota Corolla Crash in Cairo, Egypt

Crash or car bomb?

Attempts to impose traffic policies can be complicated by local circumstances and driver behaviour. In 1969 Leeming warned that there is a balance to be struck when "improving" the safety of a road:^[4]

It can safely be said that many places which look dangerous do not have accidents, or very few. Conversely, a location that does not look dangerous may have a high crash frequency. The reason for this is simple. If drivers perceive a location as hazardous, they take more care and there are no accidents. Accidents happen when hazardous road or traffic conditions are not obvious at a glance, or where the conditions are too complicated for the limited human machine to perceive and react in the time and distance available.

This phenomena has been observed in risk compensation research, where the predicted reductions in accident rates have not occurred after legislative or technical changes. One study observed that the introduction of improved brakes resulted in more aggressive driving,^[10] and another argued that compulsory seat belt laws have not been accompanied by a clearly-attributed fall in overall fatalities.^[11]

In the 1990s Hans Monderman's studies of driver behaviour led him to the realisation that signs and regulations had an adverse effect on a driver's ability to interact safely with other road users. Monderman developed shared space principles, rooted in the principles of the woonerven of the 1970s. He found that the removal of highway clutter, while allowing drivers and other road users to mingle with equal priority, could help drivers recognise environmental clues. They relied on their cognitive skills alone, reducing traffic speeds radically and resulting in lower levels of road casualties and lower levels of congestion.^[12]

Speed choice

The U.S. Department of transportation's Federal Highway Administration have a webpage documenting a review of speed research.^[13] The summary states:

• That the evidence shows that the risk of having a crash is increased both for vehicles travelling slower than the average speed, and for those travelling above the average speed.
• That the risk of being injured increases exponentially with speeds much faster than the median speed.
• That the severity of a crash depends on the vehicle speed change at impact.
• That there is limited evidence that suggests that lower speed limits result in lower speeds on a system wide basis.
• That most crashes related to speed involve speed too fast for the conditions.
• That more research is needed to determine the effectiveness of traffic calming.

On a webpage titled "The biggest killer on our roads", the Road and Traffic Authority (RTA) of the Australian state of New South Wales (NSW), state that speeding (by which they mean travelling too fast for the prevailing conditions, in addition to speed above the specified speed limit^[14]) is a factor in about 40 percent of road deaths.^[15] On the same webpage the RTA also state that "speeding increases the risk of a crash and the severity of the crash outcome".^[15] On another webpage, the RTA qualify their claims by referring to one specific piece of research from 1997, and stating "research has shown that the risk of a crash causing death or injury increases rapidly, even with small increases above an appropriately set speed limit."^[16]

The contributory factor report in the official British road casualty statistics show for 2006, that "exceeding speed limit" (known as "speeding" in the UK) was a contributory factor in 5% of all casualty crashes (14% of all fatal crashes), and that "travelling too fast for conditions" was a contributory factor in 11% of all casualty crashes (18% of all fatal crashes).^[17]

Driver impairment

A road user's capability is affected by the physical and mental ability to assess conditions and respond quickly. Studies^[18] have established some common conditions that impair this judgement, including:

• poor eyesight and/or physical impairment, with many jurisdictions setting simple sight tests and/or requiring appropriate vehicle modifications before being allowed to drive;
• old age, with some jurisdictions requiring driver retesting for reaction speed and eyesight after a certain age;
• Fatigue;
• excessive alcohol, with simple blood-alcohol limits enforced through drink-driving laws (although some level of impairment may occur below the legal limit). See also: alcohol-related traffic crashes in the United States;
• drug use - including some prescription drugs, over the counter drugs (notably antihistamines, opioids and muscarinic antagonists), and illegal drugs.

Several conditions can work together to create a much worse situation, for example:

• combining low doses of alcohol and cannabis has a more severe effect on driving performance than either cannabis or alcohol in isolation,^[19] or
• taking recommended doses of several drugs together, which individually will not cause impairment, may combine to bring on drowsiness or other impairment. This could be more pronounced in an elderly person whose renal function is less efficient than a younger person's.^[20]

Thus there are situations when a person may be impaired, but still legally allowed to drive, and becomes a potential hazard to themselves and other road users. Pedestrians or cyclists are affected in the same way and can similarly jeopardise themselves or others when on the road.

Research suggests that the driver's attention is affected by distracting sounds such as conversations and operating a mobile phone while driving. Many jurisdictions now restrict or outlaw the use of some types of phone within the car. Recent research conducted by British scientists suggests that music can also have an effect; classical music is considered to be calming, yet too much could relax the driver to a condition of distraction. On the other hand, hard rock may encourage the driver to step on the acceleration pedal, thus creating a potentially dangerous situation on the road.^[21]

 Road design

See also: Road traffic safety

A 1985 US study showed that about 34% of serious crashes had contributing factors related to the roadway or its environment. Most of these crashes also involved a human factor.^[5] The road or environmental factor was either noted as making a significant contribution to the circumstances of the crash, or did not allow room to recover. In these circumstances it is frequently the driver who is blamed rather than the road; those reporting the accident have a tendency to overlook the human factors involved, such as the subtleties of design and maintenance that a driver could fail to observe or inadequately compensate for.^[22]

A potential long fall stopped by an early guardrail, ca. 1920. Guardrails, median barriers, or other physical objects can help reduce the consequences of an accident or minimize damage.

Research has shown that careful design and maintenance, with well-designed intersections, road surfaces, visibility and traffic control devices, can result in significant improvements in accident rates. Individual roads also have widely differing performance in the event of an impact. In Europe there are now EuroRAP tests that indicate how "self-explaining" and forgiving a particular road and its roadside would be in the event of a major incident.

In the UK, research has shown that investment in a safe road infrastructure programme could yield a ⅓ reduction in road deaths saving as much as £6billion per year^[23]. A consortium of 13 major road safety stakeholders have formed the Campaign for Safe Road Design which is calling on the UK Government to make safe road design a national transport priority^[24].

Vehicle design and maintenance

See also: Automobile safety

Wreckage of a crash from Saragossa, Spain. The car, a Seat Ibiza Mk 3, suffered extensive damage but the interior was largely unscathed.

A well-designed and well-maintained vehicle, with good brakes, tires and well-adjusted suspension will be more controllable in an emergency and thus be better equipped to avoid collisions. Some mandatory vehicle inspection schemes include tests for some aspects of road worthiness, such as the UK's MOT test or German TÜV conformance inspection.

The design of vehicles has also evolved to improve protection after collision, both for vehicle occupants and for those outside of the vehicle. Much of this work was led by automotive industry competition and technological innovation, leading to measures such as Saab's safety cage and reinforced roof pillars of 1946, Ford´s 1956 Lifeguard safety package, and Saab and Volvo's introduction of standard fit seatbelts in 1959. Other initiatives were accelerated as a reaction to consumer pressure, after publications such as Ralph Nader's 1965 book Unsafe at Any Speed accused motor manufacturers of indifference towards safety.