Alcohol
The consumption of alcohol prior to driving is closely correlated with increased crash risk[1] Following the consumption of an alcoholic beverage, effects on the brain begin to be noticed within 10 minutes[2]. The effects upon the brain include reduced awareness and concentration, slower reaction times, increased confidence and assessment of abilities, and lowered ability to accurately judge risk[3], all of which impair the ability of an individual to safety operate a vehicle, and increase the risk that a crash will occur.
The chance of being involved in a serious accident rises rapidly with increased blood alcohol concentration (BAC), with studies showing an 83% increase in risk with a BAC of 0.05g/dl (5mg alcohol per deciliter of blood), over a BAC of zero[4],[5]. Above this level, the risk continues to rise dramatically, wdrivers with BAC’s between 0.051g/dl and .08mg/dl are 7.2 times more likely to be involved in a fatal crash as those who have consumed no alcohol[6]. This has seen a the legal alcohol limit reduced to 0.05 in many western countries, with New Zealand, the United Kingdom, Canada and the United States as notable exceptions. In New Zealand, alcohol is a factor in 31% of all fatal accidents, according to 2008 figures[7].
Speed
Speed is a contributing factor in up to 30% of all fatal crashes[8]. This increase in risk is related to both an increased risk of a crash occurring, and the likely increase in severity of any accident. The likelihood of being involved in a car accident increases exponentially with increasing speed, one study in Adelaide suggesting that a 10km/hr reduction in speed would reduce the number of accidents by at least 42%[9]. This study also found that risk of being involved in a fatal accident was roughly equal when travelling at 72km/hr as when having a BAC of 0.12, nearly three times Australia’s legal limit. The severity of any crash is also increased by speed, with the risk of serious injury occurring rising exponentially. The risk of being involved in a fatal accident increases by a factor of two from 60km/hr to 65km/hr, however by 70km/hr this has increased by a factor of four, and by 80km/hr by a factor of 31[10].
It is important to note that a difference exists between excess speed, that is driving above the legal speed limit, and inappropriate speed[11]. The former is what is usually measured and reported in studies considering speed as a factor, however is probably a more useful measure of how important speed was in an individual crash. This is because ‘inappropriate speed’ is not fixed, but rather varies with different weather and traffic conditions, so that a vehicle may be travelling at a speed inappropriate for current conditions, increasing the likelihood of a crash occurring, even while being under the legal speed limit.
Age
Young people are disproportionally represented in statistics of road accidents. In Australia, for example, those aged 17-25 make up 13% of the total population, yet count for 29% of total road injuries and deaths, a pattern mirrored in industrialized nations worldwide[12]. This increased risk is related both to a lack of driving experience, and the reduced ability of youth to correctly observe and analyse risk. This leads to increased risk-taking behavior such as dangerous overtaking, speeding, and generally undertaking hazardous maneuvers[13] [14].
Fatigue
Fatigue is being increasingly recognised as a contributing factor in vehicle accidents. It is particularly important for commercial drivers, due to the long hours of driving that they do, however all drivers may be affected by it at some time or another[15]. Fatigue dulls the perceptions of drivers in a manner similar to alcohol, causing a loss of concentration and focus, and subsequent lowering of ability to keep control of the vehicle[16]. At its most extreme, fatigued drivers may fall asleep at the wheel, and potentially drive either off the road, or across the centre line into the path of oncoming traffic.
Use of hand-held devices
Distractions are another major contributing factor to road accidents. The most common of these is the use of mobile telephones, which have been linked to reduced concentration and ability to maintain position and following-distance on the road, reduced decision making, and a reduced ability to correctly gauge speed as well as safe gaps in traffic flow[17]. Studies on this issue have shown that reaction times of drivers talking on the telephone are 0.5-1.5 seconds slower than usual[18], and evidence suggests there is a four times higher risk of being involved in a crash as a result of this[19].
[1] Raymond Peck, Michael Gebers, Robert Voas, Eduardo Romano (2008). ‘The relationship between blood alcohol concentration (BAC), age, and crash risk’. Journal of Safety Research, 39: 311-319
[2] Institute for Road safety Research. (2009) ‘Driving under the influence of alcohol’. http://www.swov.nl/rapport/Factsheets/UK/FS_Alcohol_UK.pdf
Accessed, October 07, 2010
[3] A.J. McLean and O.T. Holubowycz (1981). Alcohol and the risk of accident involvement. Alcohol, Drugs, and Traffic Safety. Proceedings of the 8th International Conference of Alcohol, Drugs, and Traffic Safety, Stockholm, 15-19 Hune 1980. Almqvist and Wiksell International: 113-123
[4] Raymond Peck, Michael Gebers, Robert Voas, Eduardo Romano (2008). ‘The relationship between blood alcohol concentration (BAC), age, and crash risk’. Journal of Safety Research, 39: 311-319
[5] Margie Peden, Richard Scurfield, David Sleet, Dinesh Mohan, Adnan A. Hyder, Eva Jarawan and Colin Mathers (2004). World Report on Road Traffic Injury Prevention. Geneva, World Health Organisation
[6] E. Chamberlain and R. Solomon (2002). ‘The case for a 0.05% criminal law alcohol concentration limit for driving’. Injury Prevention 8: 1-17
[7] Ministry of Transport (2009). Motor vehicle crashes in New Zealand in 2008. Report prepared by Transport Monitoring, Ministry of Transport
[8] Margie Peden, Richard Scurfield, David Sleet, Dinesh Mohan, Adnan A. Hyder, Eva Jarawan and Colin Mathers (2004). World Report on Road Traffic Injury Prevention. Geneva, World Health Organisation
[9] C. Kloeden, A McLean, V Moore and G. Ponte (1997) Travelling speed and the risk of crash involvement. University of Adelaide
[10] J McLean and C. Kloeden (2002). ‘Alcohol, travelling speed and the risk of crash involvement’ in D Mayhew and C Dassault (eds.) Proceedings of the 16th International Conference on Alcohol, Drugs and Taffic Safety, Montreal, 4-9 August 2002. Montreal, Societe de l’assurance automobile de Quebec: 73-79.
[11] Margie Peden, Richard Scurfield, David Sleet, Dinesh Mohan, Adnan A. Hyder, Eva Jarawan and Colin Mathers (2004). World Report on Road Traffic Injury Prevention. Geneva, World Health Organisation
[12] Laurence Lam (2003) ‘Factors associated with fatal and injurious car crash among
learner drivers in New South Wales, Australia’. Accident Analysis and Prevention 35: 333-340
[13] Brian Jonah (1986) ‘Accident risk and risk-taking behaviour among young drivers’. Accident Analysis & Prevention 18 (4): 255-271
[14] Margie Peden, Richard Scurfield, David Sleet, Dinesh Mohan, Adnan A. Hyder, Eva Jarawan and Colin Mathers (2004). World Report on Road Traffic Injury Prevention. Geneva, World Health Organisation
[15] J Horne and L Reyner (1999). ‘Vehicle accidents related to sleep: a review’. Occupational and Environmental Medicine 56: 289-294
[16] Ibid.
[17] I.D. Brown, A.H. Tickner and D.V.C. Simmonds (1969) ‘Interference between concurrent tasks of driving and telephoning’. Journal of AppliedPsychology, 53: 419-424
[18] Ibid.
[19] D.A. Redelmeir and R.J. Tibshirani (1997) ‘Association between cellular-telephone calls and motor vehicle collisions’. New England Journal of Medicine 336: 453-458