Costes ambientales de la dispersión urbana

Driver attitudes and belief systems

Many substance impaired drivers appear to have a belief that they are not in fact significantly impaired by alcohol or other substances possibly because of either a natural or an acquired tolerance to the effects of alcohol or other substances. People, especially males, with a family history of alcohol use disorders appear to have less subjective feelings of intoxication than people without a family history and may be more likely to drive with high blood alcohol concentrations believing that they are safe to do so as they do not ‘feel’ intoxicated. Practised heavier drinkers who have developed some degree of tolerance to alcohol appear to feel less of the sedating effects of alcohol as blood alcohol levels drop after drinking, but more of the stimulant effects as blood alcohol concentrations rise when initially drinking (Quinn and Fromme, 2011). Established heavy drinkers, who may or may not have a family history, may therefore be more likely to drive with high blood alcohol concentrations impulsively due to the stimulant effects of alcohol or less perception of driving skill impairment (Gustin and Simons, 2008). Supporting this view, Marczinsky and Fillmore (2009) observed that as blood alcohol concentrations began to fall students with a history of “binge drinking” showed an “acute tolerance to alcohol’s effect on subjective intoxication”. This effect was accompanied by an increased willingness to drive compared to “non binge drinking students”.

Albery and Guppy (1996) in an analysis of self perception of the risks of drink driving found that most people underestimate the risk for having an accident, sober or impaired, but this effect is greatest amongst people with an established history of drink driving. Anti-social attitudes also appear to have a role in repeatedly drinking and driving. In a study of recidivist drink driver perceptions of the fairness and legitimacy of legal sanctions for drink driving Freeman et al. (2006) found over half of the participants in the study had low levels of respect for the law and questioned the government’s right to tell them that they could not drink and drive.

Despite these beliefs repeat drink drivers have a greater chance of being involved in fatal and non fatal motor vehicle accidents. Twenty-eight percent of drivers killed in alcohol related accidents in New Zealand in 2003-2004 had been convicted for alcohol impaired driving within the preceding five years and a quarter of those drivers had more than one previous conviction (Ministry of Transport, 2009). Chang et al. (2002) state that of all drivers killed in motor vehicle accidents in America those with a blood alcohol concentration of 100 mgs per 100 mls of blood or greater are six times more likely to have had a prior conviction for impaired driving.

Demographic and personal factors

Various studies have identified a range of personal and background factors that are more prevalent in people who drive while substance impaired. They are however not necessarily predictive of who will choose to drive while substance impaired in the first place or who is more likely to repeatedly do so.

A longitudinal study following 43,403 Swedes born in 1966 identified that the risk of first time impaired driving conviction was significantly associated with:

• earlier criminal convictions • living rurally

• parental substance abuse • having a teenage mother

• growing up with domestic violence (Christoffersen, Soothill and Phillips, 2008)

In a longitudinal study of approximately 1000 people born in 1972 and 1973 in Dunedin self reported drinking drivers were more likely than non-impaired drivers to:

• be alcohol dependent • be male

• have lower socioeconomic status • have no academic qualifications

• drink at bars or have after-work drinks before driving

• use another substance, most commonly cannabis and/or LSD, at the same time as drinking and driving

(Morrison et al., 2002)

Figures from the Ministry of Justice indicate that repeat substance impaired drivers in New Zealand between 2006 and 2010 were more likely to be:

• male, with an increasing rate of conviction over time compared to females (Figure 5) • aged between the ages of 20 and 49, with the steepest increase in repeat offending

in the 20 to 29 year old age range (Figure 6)

• European, though Màori remain disproportionately over represented in the rates of conviction (Figure 7)

Figure 5: Gender of people with three or more substance impaired driving convictions 2006-2010 0 1,000 2,000 3,000 4,000 5,000 6,000 7,000 Male Female 1 2 3 4 5

Figure 6: Age range of people with three or more substance impaired driving convictions 2006-2010 1 2 3 4 5 0 500 1000 1500 2000 2500 20-29 30-39 Under 20 50-59 60 and over 40-49

Figure 7: Ethnicity of people with three or more substance impaired driving convictions 2006-2010 0 500 1000 1500 2000 2500 3000 3500 1 2 3 4 5 Màori European Pacific Island

Source: Ministry of Justice, 2010

Alongside factors that are common to many people involved in criminal offending it appears that repeat substance impaired drivers are also more likely than the general population to have co-existing mental health problems.

Figure 8: Comparing the prevalence of co-existing problems between repeat (2 or more) alcohol impaired driving offenders and a general community sample

0% 20% 40% 60% 80% 100%

Lifetime Disorder Prevalence

General Population Repeat DUI Offenders 3+ Past year disorders

2 Past year disorders 1 Past year disorders

3+ Past year disorders 2 Past year disorders Any Past year disorders Any Past year disorders

* * * * * * *

*Indicates a significant difference between prevalence rates Source: The DRAM 2007 (adapted from Shaffer et al., 2007).

Summarising research into the characteristics of substance impaired drivers that are predictive of a greater risk for future substance impaired driving the following factors have all been identified as being more prevalent amongst that population than the general population:

• being male • being young

• being single, separated or divorced • being indigenous

• being unemployed or working as a manual labourer • having a history of other traffic or criminal offences • problematic alcohol and/or substance and/or gambling

• having personality problems such as anti-social attitudes, poor impulse control, intermittent explosive disorder or conduct disorder

• having a co-existing disorder such as post traumatic stress disorder, generalised anxiety disorder, low mood or major depression, attention deficit disorder or bipolar affective disorder

Appendix 5: Substance impaired driving group