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Minor collisions such as this one are the most common type of crash.

A car accident or car crash is an incident in which an automobile collides with anything that causes damage to the automobile, including other automobiles, telephone poles, buildings or trees, or in which the driver loses control of the vehicle and damages it in some other way, such as driving into a ditch or rolling over. Sometimes a car accident may also refer to an automobile striking a human or animal. Car crashes — also called road traffic accidents (RTAs), traffic collisions, auto accidents, road accidents, personal injury collisions, motor vehicle accidents (MVAs), — kill an estimated 1.2 million people worldwide each year, and injure about forty times this number (WHO, 2004). In the UK the Department of Transport publish road deaths in each type of vehicle. These statistics are available as "Risk of injury measured by percentage of drivers injured in a two car injury accident." These statistics show a ten to one ratio of in-vehicle accident deaths between the least safe and most safe models of car.

The statistics show[How to reference and link to summary or text] that for popular, lightly built cars, occupants have a 6–8% chance of death in a two-car accident. (e.g. BMW 3 series 6%, Subaru Impreza 8%, Honda Accord 6%). Traditional "safety cars" such as the Volvos halve that chance (Volvo 700 4% incidence of death, Volvo 900 3%).

Motorcyclist deaths within England and Wales stand at 53% of the annual road death statistics. Scooters/mopeds up to 50cc only account for 3% of those deaths. 2% of the scooter deaths were 16–19 year olds who had not taken CBT (Compulsory Basic Training). (Statistics taken from 2004/2005 DSA annual road deaths percentages)

Trends in collision statistics

In an accident resulting from excessive speed, this concrete truck rolled over into the front garden of a house. There were no injuries, but significant damage was caused.

Road toll figures show that car collision fatalities have declined since 1980, with most countries showing a reduction of roughly 50%. This drop appears to confirm the efficacy of safety measures introduced thereafter, assuming that driver behaviour has not changed significantly.

In the United States, fatalities have increased slightly from 40,716 in 1994 to 42,884 in 2003. However, in terms of fatalities per 100 million miles driven, the fatality rate has dropped 16% between 1995 and 2005. Injuries dropped 37% over the same period. (National Traffic Safety Administration, 2006)

It has been noted that road fatality trends closely follow the so-called "Smeed's law" (after RJ Smeed, its author), an empirical rule relating injury rates to the two-thirds power of car ownership levels. An analysis by John Adams can be found here.

Backup collisions

Backup collisions happen when a driver reverses their car into an object, person, or another car. Although most cars come equipped with rear view mirrors, which are adequate for detecting vehicles behind a car, they are inadequate on many vehicles for detecting small children or objects close to the ground, which fall in the car's blind spot. Large trucks have much larger blind spots that can hide entire vehicles and large adults.

According to research by Kids and Cars – an organization devoted to preventing (non-traffic) motor-vehicle-related deaths and injuries – 49% of the non-traffic, non-crash fatalities involving children under 15 from 2001–2005 were caused by vehicles backing up.

The CDC reported that from 2001–2003, an estimated 7,475 children (2,492 per year) under the age of 15 were treated for automobile back-over incidents.

In its “Deaths and Injuries Resulting from Certain Non-Traffic and Non-Crash Events,” report issued in May of 2004, the National Highway Traffic Safety Administration found that back-up collisions most often:

  • Occur in residential driveways and parking lots
  • Involve sport utility vehicles (SUVs) or small trucks
  • Occur when a parent, relative or someone known to the family is driving
  • Particularly affect children less than five years old

The driver of the car backing up and hitting an object, a person, or another car is usually considered to be at fault.

Prevention organizations suggest that parents use common sense, and also take safety measures such as installing cross view mirrors, audible collision detectors, rear view video camera and/or some type of reverse backup sensors


  Driver factors
  27%   Roadway
  6% 3%   3%
Vehicle factors

Breakdown of British and
American crash causes

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.[1]

Psychological causes

Human factors

Human factors in vehicle collisions include all factors related to drivers and other road users that may contribute to a collision. Examples include driver behavior, visual and auditory acuity, decision-making ability, and reaction speed.

A 1985 report based on British and American crash data found driver error, intoxication and other human factors contribute wholly or partly to about 93% of crashes.[1]

An RAC survey of British drivers found that most thought they were better than average drivers; a contradictory result showing overconfidence in their abilities. Nearly all drivers who had been in a crash did not believe themselves to be at fault.[2] One survey of drivers reported that they thought the key elements of good driving were:[3]

  • 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 crashing 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.[3]

An AXA survey concluded Irish drivers are very safety-conscious relative to other European drivers. However, this does not translate to significantly lower crash rates in Ireland.[4]

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 behavior during emergencies, and their hazard perception.

There are demographic differences in crash rates. For example, although young people tend to have good reaction times, disproportionately more young male drivers feature in accidents,[5] with researchers observing that many exhibit behaviors and attitudes to risk that can place them in more hazardous situations than other road users.[3] This is 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 might 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.[6] 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:[7]

Conversely, a location that does not look dangerous may have a high crash frequency. This is, in part, because if drivers perceive a location as hazardous, they take more care. Accidents may be more likely to 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 fact can be used to improve safety, by putting up signs in accident-prone locations, like ones stated above.)

This phenomenon 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,[8] and another argued that compulsory seat belt laws have not been accompanied by a clearly attributed fall in overall fatalities.[9]

In the 1990s Hans Monderman's studies of driver behavior led him to the realization 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 recognize 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.[10]

Some crashes are intended; staged crashes, for example, involve at least one party who hopes to crash a vehicle in order to submit lucrative claims to an insurance company. [11] In the 1990s, criminals recruited Latin immigrants to deliberately crash cars, usually by cutting in front of another car and slamming on the brakes. It was an illegal and risky job, and they were typically paid only $100. Jose Luis Lopez Perez, a staged crash driver, died after one such maneuver, leading to an investigation that uncovered the increasing frequency of this type of crash.[12]

Motor vehicle speed

The U.S. Department of Transportation's Federal Highway Administration review research on traffic speed in 1998.[13] The summary states:

  • That the evidence shows that the risk of having a crash is increased both for vehicles traveling slower than the average speed, and for those traveling above the average speed.
  • That the risk of being injured increases exponentially with speeds much faster than the median speed.
  • That the severity/lethality 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.

The Road and Traffic Authority (RTA) of the Australian state of New South Wales (NSW) asserts speeding (travelling too fast for the prevailing conditions or above the posted speed limit[14]) is a factor in about 40 percent of road deaths.[15] The RTA also say speeding increases the risk of a crash and its severity.[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" 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

Driver impairment describes factors that prevent the driver from driving at their normal level of skill. Common impairments include:

Main article: Driving under the influence
File:Relative risk of an accident based on blood alcohol levels .png

Relative risk of an accident based on blood alcohol levels.[18]

In Canada 33.8% of motor vehicle deaths were associated with alcohol use.[19] See also: alcohol-related traffic crashes in the United States;

Physical impairment

Poor eyesight and/or physical impairment, with many jurisdictions setting simple sight tests and/or requiring appropriate vehicle modifications before being allowed to drive;


Insurance statistics demonstrate a notably higher incidence of accidents and fatalities among teenage and early twenty-aged drivers, with insurance rates reflecting this data. Teens and early twenty-aged drivers have the highest incidence of both accidents and fatalities among all driving age groups. This was observed to be true well before the advent of mobile phones.

Females in this age group suffer a somewhat lower accident and fatality rate than males but still well above the median across all age groups. Also within this group, the highest accident incidence rate occurs within the first year of licensed driving. For this reason many US states have enacted a zero-tolerance policy wherein receiving a moving violation within the first six months to one year of obtaining a license results in automatic license suspension. No US state allows fourteen year-olds to obtain drivers licenses any longer.

Old age

Old age, with some jurisdictions requiring driver retesting for reaction speed and eyesight after a certain age;

Sleep deprivation

The consequences of sleep deprivation can impact on the performance of cognitive processes and have important negative consequences; not only to the health of the individual, but those around them as sleep deprivation increases the risk of human-error related accidents, especially with vigilance-based tasks involving technology.[20] Research done on the increase in accidents involving sleep deprived individuals has been useful in illuminating the adverse effects and increased risk involved with lack of sleep. Reduced duration of sleep as well as an increase in time spent awake are factors that highly contribute to the risk of traffic collisions, the severity and fatality rates of which are on the same level as driving under the influence of alcohol.[21][22] This is especially relevant for young adults as they require 8–9 hours of sleep at night to overcome excessive daytime sleepiness[23] and are among the highest risk group for driving while feeling tired and sleep-deprived related crashes.[21][24]

Collision prevention

Although many crashes are caused by [[[driver behavior]] that is difficult to alter, by mechanical failure, or by road conditions, some technical solutions would automatically detect how close the driver is to the car in front and automatically adjust the car's acceleration to prevent the car from getting closer than the distance in which it can safely stop.

  • Sobriety detectors: These locks prevent the ignition key from working if the driver breathes into one and is shown to have consumed alcohol.
  • Drifting monitors: These devices monitor how close a vehicle is traveling to lane markers and, if it starts to drift toward or over the markers without the turn signal being activated, sounds an alarm.
Drug use

Including some prescription drugs, over the counter drugs (notably antihistamines, opioids and muscarinic antagonists), and illegal drugs.


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.[25]

Combinations of factors

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,[26] or
  • Taking recommended doses of several drugs together, which individually do 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.[27]

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 jeopardize themselves or others when on the road.


A large body of knowledge has been amassed on how to prevent car crashes, and reduce the severity of those that do occur. See Road Traffic Safety.

United Nations response

Owing to the global and massive scale of the issue, with predictions that by 2020 road traffic deaths and injuries will exceed HIV/AIDS as a burden of death and disability,[28] the United Nations and its subsidiary bodies have passed resolutions and held conferences on the issue. The first United Nations General Assembly resolution and debate was in 2003[29] The World Day of Remembrance for Road Traffic Victims was declared in 2005. In 2009 the first high level ministerial conference on road safety was held in Moscow.

The World Health Organization, a specialized agency of the United Nations Organization, in its Global Status Report on Road Safety 2009, states that over 90% of the world’s fatalities on the roads occur in low-income and middle-income countries, which have only 48% of the world’s registered vehicles, and predicts that road traffic injuries will rise to become the fifth leading cause of death by 2030 [30]


Main article: Epidemiology of motor vehicle collisions
File:Road traffic accidents world map - Death - WHO2004.svg

Deaths for road traffic accidents per 100,000 inhabitants in 2004.[31]

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File:Traffic related deaths - Road fatalities per vehicle-km.svg

Road fatalities per vehicle-km (fatalities per 1 billion km)

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Worldwide it was estimated in 2004 that 1.2 million people were killed (2.2% of all deaths) and 50 million more were injured in motor vehicle collisions.[32][33] India recorded 105,000 traffic deaths in a year, followed by China with over 96,000 deaths.[34] This makes motor vehicle collisions the leading cause of injury death among children worldwide 10 – 19 years old (260,000 children die a year, 10 million are injured)[35] and the sixth leading preventable cause of death in the United States[36] (45,800 people died and 2.4 million were injured in 2005).[37] In Canada they are the cause of 48% of severe injuries.[38]

See also


  1. 1.0 1.1 Harry Lum & Jerry A. Reagan Interactive Highway Safety Design Model: Accident Predictive Module. Public Roads Magazine.
  2. I'm a good driver: you're not!.
  3. 3.0 3.1 3.2 (January 2007) The Good, the Bad and the Talented: Young Drivers' Perspectives on Good Driving and Learning to Drive (PDF), Road Safety Research Report No. 74, Transport Research Laboratory. URL accessed 2008-01-04.
  4. Home. Galway Independent. URL accessed on 2012-01-15.
  5. Thew, Rosemary (2006). Royal Society for the Prevention of Accidents Conference Proceedings. (PDF) Driving Standards Agency.
  6. forecasting older driver's accident rates. Department for Transport.
  7. Cite error: Invalid <ref> tag; no text was provided for refs named leeming
  8. Sagberg, Fosser, & Saetermo (1997). An investigation of behavioral adaptation to airbags and antilock brakes among taxi drivers, 29, 293–302, Accident Analysis and Prevention.
  9. Adams, John (1982). The efficacy of seat belt legislation. (PDF) SAE Transactions.
  10. Ben Hamilton-Baillie (Autumn 2005). Streets ahead.
  11. Lascher, Edward L. and Michael R. Powers. “The economics and politics of choice no-fault insurance.” Springer, 2001
  12. Dornstein, Ken. “Accidentally, on Purpose: The Making of a Personal Injury Underworld in America.” Palgrave Macmillan, 1998, p.3
  13. Synthesis of Safety Research Related to Speed and Speed Limits. U.S. Department of Transportation. URL accessed on 2008-03-05.
  14. Problem definition and countermeasures. NSW Roads and Traffic Authority. URL accessed on 2008-05-20.
  15. 15.0 15.1 The biggest killer on our roads. NSW Roads and Traffic Authority. URL accessed on 2008-03-05.
  16. Speeding research. NSW Roads and Traffic Authority. URL accessed on 2008-03-05.
  17. Road Casualties Great Britain: 2006. (PDF) UK Department for Transport. URL accessed on 2008-03-05.
  19. (PDF) Transport Canada.
  20. Dinges DF. (1995) An overview of sleepiness and accidents. Journal of Sleep Research, 4,4–11
  21. 21.0 21.1 Pack AI, Pack AM, Rodgman E, Cucchiara A, Dinges DF, Schwab CW. (1995) Characteristics of crashes attributed to the driver having fallen asleep. Accident Analysis and Prevention, 27, 769–775
  22. Stutts JC, Wilkins JW, Osberg JS, Vaughn BV.(2003) Driver risk factors for sleep-related crashes. Accid Anal Prev,35, 321-331
  23. Roehrs TA, Timms V, Zwyghuizen-Doorenbos A, Roth T. (1989) Sleep extension in sleepy and alert normals. Sleep, 12, 449-457
  24. Carskadon MA.(1989-1990) Adolescent sleepiness: increased risk in a high-risk population. Alcohol, Drugs and Driving,5-6,317–328
  25. Hard-Rock and Classic Music Could Lead to Road Accidents, New Survey Says. URL accessed on 2011-11-13.
  26. (Spring 2003) Road Safety Part 1: Alcohol, drugs, ageing & fatigue, Research summary, TRL Report 543, UK Department for Transport. URL accessed 2008-01-01.
  27. (Spring 2003) Road Safety Part 1: Alcohol, drugs, ageing & fatigue, Research summary, Transport Research Laboratory Road Safety Report No. 24, UK Department for Transport. URL accessed 2008-01-01.
  28. Template:UN document
  29. Template:UN document
  30. Road Traffic Deaths Index 2009 Country Rankings. URL accessed on 1010-02-02.
  31. (2004). WHO Disease and injury country estimates. World Health Organization. URL accessed on Nov. 11, 2009.
  32. Cite error: Invalid <ref> tag; no text was provided for refs named
  33. World Health Organization.
  34. ´"Nearly 300 Indians die daily on roads, shows report". Business Standard. August 17, 2009.
  35. includeonly>"BBC NEWS | Special Reports | UN raises child accidents alarm", BBC News, 2008-12-10. Retrieved on 2010-05-25.
  36. Mokdad AH, Marks JS, Stroup DF, Gerberding JL (March 2004). Actual causes of death in the United States, 2000. JAMA 291 (10): 1238–45.
  37. Report on Injuries in America :: Making Our World Safer.
  38. Motor Vehicle Collisions Most Frequent Cause of Severe Injuries.

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