Risk compensation is a theory which tries to understand the behavior of people engaging in potentially hazardous activities. It refers to the tendency of people to adjust their behavior in response to the perceived level of risk, behaving less cautiously where they feel more protected and more cautiously where they feel a higher level of risk. The theory emerged from road safety research after it was observed that many interventions failed to achieve the expected level of benefits but has since found application in many other fields.
Risk compensation is related to the broader term behavioral adaptation which includes all behavior changes in response to safety measures, whether compensatory or not. However, since researchers are primarily interested in the compensatory or negative adaptive behavior the terms are sometimes used interchangeably.
Notable examples include observations of increased levels of risky behavior by road users following the introduction of compulsory seatbelts and bicycle helmets and motorists driving faster and following more closely behind the vehicle in front following the introduction of anti-lock brakes. However this effect may be small compared to the fundamental benefits of these interventions, resulting in a net safety benefit, albeit one slightly smaller than was expected.
- 1 Examples
- 2 Peltzman effect
- 3 Risk homeostasis
- 4 See also
- 5 References
- 6 Other sources
- 7 External links
Anti-lock braking systems are designed to increase vehicle safety by reducing skidding.
A number of studies show that drivers of vehicles with ABS tend to drive faster, follow closer and brake later, accounting for the failure of ABS to result in any measurable improvement in road safety. The studies were performed in Canada, Denmark and Germany. A study led by Fred Mannering, a professor of civil engineering at Purdue University supports risk compensation, terming it the "offset hypothesis". A study of crashes involving taxicabs in Munich of which half had been equipped with anti-lock brakes noted that crash rate was substantially the same for both types of cab, and concluded this was due to drivers of ABS-equipped cabs taking more risks.
However, the Insurance Institute for Highway Safety released a study in 2010 that found motorcycles with ABS 37% less likely to be involved in a fatal crash than models without ABS. A 2004 study found that ABS reduced the risk of multiple vehicle crashes by 18 percent, but had increased the risk of run-off-road crashes by 35 percent.
In Britain in 1981 at a time when the government was considering the introduction of seat belt legislation, John Adams, of University College London, suggested that there was no convincing evidence of a correlation between the seat-belt legislation and reductions injuries and fatalities based on a comparison between states with and without seat belt laws. He also suggested that some injuries were displaced from car drivers to pedestrians and other road users. The 'Isles Report' echoed these concerns. Adams subsequently argued that the reduction in fatalities that followed the introduction of legislation could not be attributed with confidence to seat-belt use due to the simultaneous introduction of breath testing for driving under the influence of alcohol.
However, a 2007 study based on data from the Fatality Analysis Reporting System (FARS) of the National Highway Traffic Safety Administration concluded that between 1985 and 2002 there were "significant reductions in fatality rates for occupants and motorcyclists after the implementation of belt use laws", and that "seatbelt use rate is significantly related to lower fatality rates for the total, pedestrian, and all non-occupant models even when controlling for the presence of other state traffic safety policies and a variety of demographic factors."
Swedish change to driving on the right
In Sweden, following the change from driving on the left to driving on the right there was a drop in crashes and fatalities, which was linked to the increased apparent risk. The number of motor insurance claims went down by 40%, returning to normal over the next six weeks. Fatality levels took two years to return to normal.
Shared space is a relatively new approach to the design of roads, where the level of uncertainty for drivers and other road users is deliberately increased by removing traditional demarcations between vehicle traffic such as railings and traffic signals, and has been observed to result in lower vehicle speeds and fewer road casualties. Shared space seeks to minimise demarcations between vehicle traffic and pedestrians, often by removing features such as curbs, road surface markings, traffic signs and regulations. Typically used on narrower streets within the urban core and as part of living streets within residential areas, the approach has also been applied to busier roads, including Exhibition Road in Kensington, London.
Schemes are often motivated by a desire to reduce the dominance of vehicles, vehicle speeds and road casualty rates. First proposed in 1991, the term is now strongly associated to the work of Hans Monderman who suggested that by creating a greater sense of uncertainty and making it unclear who had right of way, drivers reduce their speed, and everyone reduces their level of risk compensation. The approach is frequently opposed by organisations representing the interests of blind, partially sighted and deaf who often express a strong preference for the clear separation of pedestrian and vehicular traffic.
There is strong evidence that reducing speed limits normally reduces crash, injury and fatality rates, for example, a 2003 review of changes to speed limits in a number of jurisdictions showed that in most cases where speed limits had been decreased that the number of crashes and fatalities had decreased and that where speed limits had been increased the number of crashes and fatalities had increased.
A 1994 study by Jeremy Jackson and Roger Blackman using a driving simulator, reported that increased speed limits and a reduction of speeding fines had significantly increased driving speed but resulted in no change in the accident frequency. It also showed that increased accident cost caused large and significant reductions in accident frequency but no change in speed choice. The abstract states that the results suggest that regulation of specific risky behaviors such as speed choice may have little influence on accident rates.
The issue of risk compensation has been a central topic in the heated debate concerning the effectiveness of Bicycle helmet use and legislation. See Bicycle Helmet (Risk compensation section) for details.
Recent studies indicate that skiers wearing helmets go faster on average than non-helmeted skiers, and that overall risk index is higher in helmeted skiers than non-helmeted skiers. Moreover, while helmets may help prevent minor head injuries, increased usage of helmets has not reduced the overall fatality rate.
Other recent studies have concluded that helmet use is not associated with riskier behavior among skiers and snowboarders, and that helmet usage reduces the risk and severity of head injuries.
'Booth's rule #2', often attributed to skydiving pioneer Bill Booth, states that "The safer skydiving gear becomes, the more chances skydivers will take, in order to keep the fatality rate constant". Even though skydiving equipment has made huge leaps forward in terms of reliability, including the introduction of safety devices such as AADs, the fatality rate has stayed roughly constant when adjusted for the increasing number of participants. This can largely be attributed to an increase in the popularity of high performance canopies, which fly much faster than traditional parachutes. A greater number landing fatalities in recent years has been attributed to high speed manoeuvres close to the ground.
Safety equipment in children
Experimental studies have suggested that children who wear protective equipment are likely to take more risks.
Risky sexual behavior and HIV/AIDS
Evidence on risk compensation associated with HIV prevention interventions is mixed. Harvard researcher Edward C. Green argued that the risk compensation phenomenon could explain the failure of condom distribution programs to reverse HIV prevalence, providing a detailed explanations of his views in an op-ed article for The Washington Post and an extended interview with the BBC. A 2007 article in the Lancet suggested that "condoms seem to foster disinhibition, in which people engage in risky sex either with condoms or with the intention of using condoms". Another report compared risk behaviour of men based on whether they were circumcised.
The Peltzman effect is the hypothesized tendency of people to react to a safety regulation by increasing other risky behavior, offsetting some or all of the benefit of the regulation. It is named after Sam Peltzman, a professor of Economics at the University of Chicago Booth School of Business. When the offsetting risky behavior encouraged by the safety regulation has negative externalities, the Peltzman effect can result in redistributing risk to innocent bystanders who would behave in a risk-averse manner even without the regulation. For example, if some risk-tolerant drivers who would not otherwise wear a seat belt respond to a seat belt law by driving less safely, there would be more total collisions. Overall injuries and fatalities may still decrease due to greater seat belt use, but drivers who would wear seat belts regardless would see their overall risk increase. Similarly, safety regulations for automobiles may put pedestrians or bicyclists in more danger by encouraging risky behavior in drivers without offering additional protection for pedestrians and cyclists.
The Peltzman effect has been used to explain Smeed's Law, an empirical claim that traffic fatality rates increase with the number of vehicle registrations per capita, and differing safety standards have no effect. Recent empirical studies have rejected Smeed's Law, which is inconsistent with the observation of declining fatality rates in many countries, along with the associated theory of risk homeostasis (see below). . Roy Baumeister has suggested that the use of helmets in American football and gloves in boxing lead to examples of the Peltzman effect.
Risk homeostasis is a theory developed by Gerald J. S. Wilde, a professor emeritus of psychology at Queen's University, Kingston, Ontario, Canada. It states that humans optimize their level of risk according to four utility factors:
- The expected benefits of risky behavior (examples: gaining time by speeding, fighting boredom, increasing mobility).
- The expected costs of risky behavior (examples: speeding tickets, car repairs, insurance surcharges).
- The expected benefits of safe behavior (examples: insurance discounts for accident-free periods, enhancement of reputation of responsibility).
- The expected costs of safe behavior (examples: using an uncomfortable seat belt, being called a coward by one's peers, time loss).
The level of risk that provides the greatest net benefit is termed the target level of risk. The theory predicts that people will compare their target level of risk to the perceived level of risk and adjust their behavior until the two are equal. When safety measures are introduced, the added sense of protection prompts drivers to engage in riskier behavior to optimize the cost/benefits of the four utility factors, and the overall risk remains basically the same in spite of the safety measures.
Wilde noted that when Sweden changed from driving on the left to driving on the right in 1967, this was followed by a marked reduction in the traffic fatality rate for 18 months after which the trend returned to its previous values. It was suggested that drivers had responded to increased perceived danger by taking more care, only to revert to previous habits as they became accustomed to the new regime. This hypothesis is elucidated in Wilde's book.
In a Munich study, part of a fleet of taxicabs were equipped with anti-lock brakes (ABS), while the remainder had conventional brake systems. In other respects, the two types of cars were identical. The crash rates, studied over 3 years, were a little higher for the cabs with ABS, and Wilde concluded that drivers of ABS-equipped cabs took more risks, assuming that ABS would take care of them; non-ABS drivers were said to drive more carefully since they could not rely on ABS in a dangerous situation. Likewise, it has been found that drivers behave less carefully around bicyclists wearing helmets than around unhelmeted riders.
The idea of risk homeostasis is controversial; some consider its views "extreme". It has not attracted widespread support. Some critics say that risk homeostasis theory is contradicted by car crash fatality rates. These rates have fallen after the introduction of seat belt laws.
- "Risk compensation is the term given to a theory which tries to understand the behaviour of people in potentially hazardous activities. In the context of the road user, risk compensation refers to the tendency of road users to compensate for changes in the road system that are perceived as improving safety by adapting behaviour (Elvik and Vaa,2004). So measures, designed to improve traffic safety, may bring along negative consequences in a way that individuals increase the riskiness of their driving behaviour because they feel safer (Dulisse, 1997)." Behavioural Adaptation, RiskCompensation, Risk Homeostasis and Moral Hazard in Traffic Safety Literature Review Klara Vrolix Steunpunt Verkeersveiligheid, September 2006 https://doclib.uhasselt.be/dspace/bitstream/1942/4002/1/behavioraladaptation.pdf
- "The early risk compensation literature deals with road safety... Several recent studies examine risk compensation in response to both aggregate and specific consumer product and workplace safety regulations." James Hedlund Risky business: safety regulations, risk compensation, and individual behavior Inj Prev 2000;6:82-89 doi:10.1136/ip.6.2.82 http://injuryprevention.bmj.com/content/6/2/82.long#sec-7
- "A term, closely related to risk compensation, is ‘behavioural adaptation’. Behavioural adaptation is a wider term referring to all behavioural changes triggered by a safety measure (OECD, 1997). Strictly spoken, this includes all positive and negative behavioural changes induced by road safety measures. Nevertheless, the emphasis is primarily put on the negative aspects of this phenomenon."Behavioural Adaptation, Risk Compensation, Risk Homeostasis and Moral Hazard in Traffic Safety Literature Review Klara Vrolix Steunpunt Verkeersveiligheid, September 2006 https://doclib.uhasselt.be/dspace/bitstream/1942/4002/1/behavioraladaptation.pdf
- "Behavioural adaptation generally does not eliminate the safety gains from programmes, but tends to reduce the size of the expected effects." Behavioural Adaptation, Risk Compensation, RiskHomeostasis and Moral Hazard in Traffic Safety - Literature Review Klara Vrolix Steunpunt Verkeersveiligheid, September 2006 https://doclib.uhasselt.be/dspace/bitstream/1942/4002/1/behavioraladaptation.pdf
- Grant and Smiley, "Driver response to antilock brakes: a demonstration on behavioural adaptation" from Proceedings, Canadian Multidisciplinary Road Safety Conference VIII, June 14–16, Saskatchewan 1993.
- Sagberg, Fosser, and Saetermo, "An investigation of behavioural adaptation to airbags and antilock brakes among taxi drivers" Accident Analysis and Prevention #29 pp 293–302 1997.
- Aschenbrenner and Biehl, "Improved safety through improved technical measures? empirical studies regarding risk compensation processes in relation to anti-lock braking systems". In Trimpop and Wilde, Challenges to Accident Prevention: The issue of risk compensation behaviour (Groningen, NL, Styx Publications, 1994).
- Venere, Emil (2006-09-27). "Study: Airbags, antilock brakes not likely to reduce accidents, injuries". Purdue University News Service.
- Gerald J. S. Wilde (1994). "7. Remedy by engineering?". Psyc.queensu.ca. Retrieved 2010-12-07.
- "Motorcycle ABS: Skepticism Debunked". Ultimate Motorcycling. 2012-05-16. Retrieved 2012-08-18.
- "Effectiveness of ABS and Vehicle Stability Control Systems" (PDF). Royal Automobile Club of Victoria. April 2004. Retrieved 2010-12-07.
- Janssen, W. (1994). "Seat belt wearing and driving behaviour: An instrumented-vehicle study Apr; Vol 26(2)". Accident Analysis and Prevention. pp. 249–2.
- "The efficacy of seatbelt legislation: A comparative study of road accident fatality statistics from 18 countries". Dept of Geography, University College, London. 1981.
- "Isles Report".
- Adams (1995). "The Failure of Seat Belt Legislation".
- Houston, David J., and Lilliard E. Richardson. "Risk Compensation or Risk Reduction? Seatbelts, State Laws, and Traffic Fatalities." Social Science Quarterly (Blackwell Publishing Limited) 88.4 (2007): 913–936. Business Source Complete. EBSCO. Web. 9 June 2011.
- Risk and Freedom: Record of Road Safety Regulation. John Adams. Brefi Press 1985. ISBN 978-0948537059
- "On the day of the change, only 150 minor accidents were reported. Traffic accidents over the next few months went down. ... By 1969, however, accidents were back at normal levels. Dagen H: The day Sweden switched sides of the road Washington Post http://www.washingtonpost.com/blogs/blogpost/post/dagen-h-the-day-sweden-switched-sides-of-the-road-photo/2012/02/17/gIQAOwFVKR_blog.html
- "On September 4 there were 125 reported traffic accidents as opposed to 130-196 from the previous Mondays. No traffic fatalities were linked to the switch. In fact, fatalities dropped for two years, possibly because drivers were more vigilant after the switch." Sweden finally began driving on the right side of the road in 1967 The Examiner Sept 2, 2009
- "An example of risk overestimation in the short run is offered by the experience in Sweden when that country changed from left- to right-hand driving in the fall of 1967. This intervention led to a marked surge in perceived risk that exceeded the target level and thus was followed by a very cautious behavior that caused a major decrease in road fatalities. ...the accident rate returned to 'normal' within 2 years." Behavioural Adaptation and Road Safety: Theory, Evidence and Action CRC Press ISBN 13:978-1-4398-5667-3 page 67 http://books.google.com/books?id=F8HfuHnFbCMC&printsec=frontcover#v=onepage&q&f=false
- British Columbia Ministry of Transportation (2003). "Review and Analysis of Posted Speed Limits and Speed Limit Setting Practices in British Columbia". p. 26 (tables 10 and 11). Retrieved 2009-09-17.
- Jackson JSH, Blackman R (1994). A driving-simulator test of Wilde's risk homeostasis theory. Journal of Applied Psychology.
- "The average speed for helmet users of 45.8 km/h (28.4 mph) was significantly higher than those not using a helmet at 41.0 km/h (25.4 mph)." How Fast Do Winter Sports Participants Travel on Alpine Slopes? Shealy, JE. Rochester Institute of Technology, Rochester, NY, USA. Ettlinger, CF. Vermont Safety Research, Underhill Center, VT, USA. Johnson, RJ. McClure Musculoskeletal Research Center, University of Vermont College of Medicine, Burlington, VT, USA. Journal of ASTM International Volume 2, Issue 7 (July/August 2005) doi:10.1520/JAI12092
- "The main findings of this study indicate that the overall Risk Index is higher in helmeted skiers than nonhelmeted skiers. The population that contributes the most to the overall Risk Index value is male helmet wearers, signifying that male helmet wearers take more risks while skiing than others." Lana Ružić & Anton TudorRisk-taking Behavior in Skiing Among Helmet Wearers and Nonwearers Wilderness & Environmental Medicine Volume 22, Issue 4, December 2011, Pages 291–296
- "This paper presents results that suggest that while helmets may be effective at preventing minor injuries, they have not been shown to reduce the overall incidence of fatality in skiing and snowboarding even though as many as 40 % of the population at risk are currently using helmets." Shealy, Jasper E. et al Do Helmets Reduce Fatalities or Merely Alter the Patterns of Death? Journal of ASTM International (JAI) Volume 5, Issue 10 (November 2008)
- "Factors associated with self-reported risk-taking behaviour on ski slopes". Br J Sports Med 44 (3): 204–6. February 2010. doi:10.1136/bjsm.2009.066779. PMID 20231601. "Helmet use is not associated with riskier behaviour on slopes. In addition, helmet use has to be recommended because helmet use reduces the risk of head injuries among skiers and snowboarders."
- "Factors associated with self-reported risk-taking behaviour on ski slopes". Br J Sports Med 44 (3): 204–6. February 2010. doi:10.1136/bjsm.2009.066779. PMID 20231601. "Safety helmets clearly decrease the risk and severity of head injuries in skiing and snowboarding and do not seem to increase the risk of neck injury, cervical spine injury, or risk compensation behavior."
- "Testing the risk compensation hypothesis for safety helmets in alpine skiing and snowboarding". Inj. Prev. 13 (3): 173–7. June 2007. doi:10.1136/ip.2006.014142. PMC 2598370. PMID 17567972. "No evidence of risk compensation among helmet wearers was found."
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- "On risk: perception and direction". pp. 364–365. "his finding is in alignment with risk compensation theory because it predicts that, essentially, skydivers will compensate for any new safety mechanism and consequently perform more dangerous types of jumping"
- "US Skydiving Fatalities History".
- Understanding children's injury-risk behavior: Wearing safety gear can lead to increased risk taking. Morrongiello BA, Walpole B, and Lasenby J. Accident Analysis & Prevention Volume 39, Issue 3, May 2007, Pages 618–623
- Green, Edward C. (2009-03-29). "The Pope May Be Right". The Washington Post.
- "The pope was right about condoms, says Harvard HIV expert". Sunday Sequence. BBC Radio Ulster. 2009-03-29.
- Shelton, James D (2007-12-01). "Ten myths and one truth about generalised HIV epidemics". The Lancet 370 (9602): 1809–1811. doi:10.1016/S0140-6736(07)61755-3.
- Gray, Ronald, et al; Kigozi, Godfrey; Serwadda, David; Makumbi, Frederick; Watya, Stephen; Nalugoda, Fred; Kiwanuka, Noah; Moulton, Lawrence H et al. (2007-02-01). "Male circumcision for HIV prevention in men in Rakai, Uganda: a randomised trial". The Lancet 369 (9562): 657–666. doi:10.1016/S0140-6736(07)60313-4. PMID 17321311.
- Wilson, Nicholas, Wentao Xiong, and Christine Mattson (2011). "Is Sex Like Driving? Risk Compensation Associated with Randomized Male Circumcision in Kisumu, Kenya". Williams College Economics Department Working Paper Series.
- Wilde, Gerald J.S. (2001). Target Risk 2: A New Psychology of Safety and Health. ISBN 0-9699124-3-9.
- "Over a period of 36 months they observed part of a taxi fleet in Munich, Germany. Half of the observed vehicles were equipped with an anti-lock braking system (ABS)... The overall accident rate showed a slight increase for ABS taxis, but no significant differences between cars with the superior brake-system (ABS) versus cars without the system." The Psychology of Risk Taking Behavior R.M. Trimpop ISBN 0 444 89961 8 1994 page 219 http://books.google.com/books?id=rI4c24VTriEC
- "Cyclists who wear protective helmets are more likely to be knocked down by passing vehicles, new research from Bath University suggests. The study found drivers tend to pass closer when overtaking cyclists wearing helmets than those who are bare-headed." BBC News Wearing helmets 'more dangerous' http://news.bbc.co.uk/2/hi/uk_news/england/somerset/5334208.stm
- ""What set the debate alight, rather like petrol on flames, was the proposition in 1982 that road users did not just adapt to perceptions of changing risk through compensatory behaviors, but that the process was a homeostatic one, producing overall equilibrium in safety-related outcomes." Oliver Carsten Early Theories of Behavioural Adaptations in Behavourial Adaptation and Road Safety: Theory, Evidence and Action ed Christina Rudin-Brown, Samantha Jamson CRC Press, 2013 ISBN 1439856672, 9781439856673 page 28
- O'Neill B, Williams A (June 1998). "Risk homeostasis hypothesis: a rebuttal". Inj. Prev. 4 (2): 92–3. doi:10.1136/ip.4.2.92. PMC 1730350. PMID 9666359.
- "The extreme views of risk homeostasis have attracted little support." James Hedlund Risky business: safety regulations, risk compensation, and individual behavior Inj Prev 2000;6:82-89 doi:10.1136/ip.6.2.82 http://injuryprevention.bmj.com/content/6/2/82.long
- '...risk homeostasis theory should be rejected because there is no convincing evidence supporting it and much evidence refuting it." Leonard Evans Risk Homeostasis Theory and Traffic Accident Data Risk Analysis Volume 6, Issue 1, pages 81–94, March 1986 http://onlinelibrary.wiley.com/doi/10.1111/j.1539-6924.1986.tb00196.x/abstract
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- Behavioural Adaptation, Risk Compensation, RiskHomeostasis and Moral Hazard in Traffic Safety - Literature Review Klara Vrolix
- 'Naked' streets are safer, say Tories – The Times
- Sam Peltzman on IDEAS at RePEc
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