The overall purpose of the research described in this report was to establish a quantitative picture of the type and extent of drugged driving in New Zealand and investigate the level of driving impairment produced by the more commonly used drugs, both legal and illegal. The research had five main objectives: 1 Conduct a statistically representative stratified telephone survey of New Zealand drivers to provide accurate and up-to-date information about the incidence of legal and illegal drugs consumed in New Zealand prior to driving. 2 Based on information collected in the survey, conduct a follow-up survey of drivers who had indicated they drove after drug use to determine the timing, type and extent of driving, presence of other vehicle occupants, and whether any self-selected countermeasures were used. 3 Carry out a systematic review of the available research literature on the degree of driving impairment produced by the most commonly taken drugs in New Zealand. 4 Conduct an internet survey of drivers’ attitudes and perceptions of drugged driving, including the use of prescription drugs 5 Investigate the feasibility and approval requirements for establishing a procedure to obtain toxicology reports (based on blood samples) of trauma patients admitted to Waikato hospital as a result of a motor vehicle crash. Phase 1 of the telephone survey focused on the incidence of drugged driving in New Zealand. A stratified sample (n=2,000; mean age = 47.62 years; 59.30% female) of drivers (representative of the age and gender of licensed drivers) from across New Zealand completed the telephone survey. Participants were asked to indicate if they took or used any prescription medications, over-the-counter medication, or drugs for recreational purposes. Specifically they were asked about their use of alcohol, amphetamine/ methamphetamine, anti-anxiety drugs, antidepressants, anti-nausea medication, anti-psychotics, cannabis, cocaine/crack, ecstasy, kava, hallucinogens, strong painkillers, opiates, party pills, prescription stimulants, sedatives and synthetic cannabis. Of those surveyed, the drugs (other than alcohol) most commonly taken within three hours prior to driving were strong painkillers (9.81%), antidepressant medication (6.05%), anti-nausea medication (3.50%), cannabis (2.55%) and anti-anxiety medication (2.86%). Information regarding the incidence of drugged driving was also obtained from the internet survey. Participants completing the online survey (n = 434; mean age = 34.54 years; 63.59% female) were younger compared with the telephone survey participants and the percentage of those driving within three hours of taking drugs was generally higher. The drugs taken most frequently just prior to driving were the same as in the phone survey: strong opioid-based painkillers (16.59%), antidepressant medication (14.29%), cannabis (12.67%), anti-nausea medication (5.76%) and anti-anxiety medication (5.53%). Because the individual drugs belonging to some of these prescription medication types can have quite different actions, for analysis of their impairing effects they were re-classified by their mechanism of action (eg selective serotonin re-uptake inhibitors (SSRI)) rather than the illness they were prescribed to treat (eg antidepressants). Examining the drivers’ characteristics associated with the specific drug types revealed some interesting differences between these drugged driving sub-groups. For example, the majority of those taking strong opioid-based painkillers within three hours of driving were female (58.80%) with an average age of 41.67 years. The average age of those taking SSRIs was similar (41.73 years) but there was an even greater proportion of females (78.70%). The benzodiazepine (BZD) users were slightly younger (mean age = 38.44 years) and again, over half of the sample was female (60.60%). Participants using prescription stimulants prior to driving were on average aged 39.33 years, and half of the sample were female. The respondents reporting driving within three hours of using illegal substances (cannabis and amphetamine/methamphetamine) were generally younger (mean age = 30.32 years and 30.90 years respectively) and 59.60% of the cannabis users were male. The follow-up phone survey focused on participants (n = 450, mean age = 48.10 years, 57.11% female) who reported taking strong painkillers (eg codeine, tramadol, methadone, morphine), SSRIs (fluoxetine, citalopram, paroxetine and sertraline), BZDs (diazepam, lorazepam, alprazolam), cannabis and stimulants (amphetamine, methamphetamine, methylphenidate). A significant proportion of the phone (16.59%) and internet survey participants (9.95%) reported taking combinations of different drugs prior to driving. The drug combinations frequently involved alcohol (43.01% overall), and different types of strong painkillers were often combined. Using the information from the telephone survey regarding the most commonly used drugs, a systematic review was conducted to determine the degree of driving impairment caused by those drugs. The review focused on studies published between 2005 and 2015 and also drew on findings from the Driving Under the Influence of Drugs, Alcohol and Medicines project (DRUID) project funded by the EU 6th Framework Programme. The systematic review findings indicated that cannabis, opioid-based pain killers and BZDs are associated with increased crash risk. Controlled studies have shown that cannabis and BZDs impairdriving-related skills, while codeine and oxycodone may have impairing effects. The effects of morphine and methadone are unclear due to variable results in the literature and a lack of reliable data. There is currently little evidence that SRRIs or tramadol are associated with increased crash risk or produce driving-related impairments, but in both cases further research is needed. In terms of the effects of stimulants on driving, most studies report improvements in driving-related performance (eg reaction time), but they may lead to increased risk taking and they do not compensate for the effects of fatigue. As described above, many drivers take more than one drug prior to driving. Combinations of BZDs or cannabis with alcohol lead to high levels of driving-related impairment, with estimates suggesting the odds ratios for crash risk are multiplicative (rather than additive) when substances are taken together. The results of present surveys revealed that the extent of drugged driving in New Zealand is widespread, with over 50% of the participants who took SSRIs, BZDs or methylphenidate reporting ‘drugged driving’ once a week or more in the last 12 months. The proportion of those driving once a week or more was smaller for those driving after taking cannabis (42.6%), illegal stimulants (28.2%) and strong painkillers (25.5%). These proportions were similar to those indicating that it was ‘very likely’ they would drive within three hours of taking the drugs in the future. The timing of drug use differed markedly by drug type, with driving after legal/prescription drugs most frequently occurring in the morning prior to going to work or going shopping, and driving after cannabis use typically occurred in the evening (no data was available for stimulants). There was evidence that the respondents were aware of the potentially impairing effects of the drugs on their driving behaviour with over half of the cannabis users, almost 40% of those taking strong painkillers and a quarter of those taking BZDs and deciding not to drive within three hours of taking the drugs. The main reason given was they thought their driving was negatively affected and they were worried for the safety of others. Only a small proportion of those taking SSRIs or stimulants had decided not to drive after taking them during the last 12 months (8.5% and 4.5% respectively). Cannabis users were also most likely to report changing when they took their drugs or changing when they drove after taking cannabis (50% in each case). For strong painkillers, SSRIs and BZDs, fewer than 20% of respondents reported using either strategy in the last 12 months. Participants were also asked to provide a rating of the level of impairment produced by the drug they consumed. Cannabis was rated as producing the greatest impairment (2.8/10), followed by alcohol, strong painkillers, SSRIs and BZDs. Cannabis users also rated their driving speed and their ability to react to changing traffic as slower when driving after cannabis use compared with driving drug free. When asked to rate the degree of impairment produced by a range of different drugs in an average driver, hallucinogens, opiates, cocaine and stimulants were rated as most impairing and anti-nausea medication, antidepressants and anti-anxiety drugs were rated the least impairing. Attitudes to drugged driving appeared to be primarily influenced by the legality of the drug being taken, with over 60% of participants stating they totally disagreed with the statement that ‘it is ok to use illegal drugs and drive if you feel your driving skills have not been affected’. For prescription medications, however, opinions were nearly evenly divided, with almost a third agreeing with the statement and another third disagreeing with the statement. There was greater consensus with regard to police enforcement of alcohol, with over 80% of respondents believing that random roadside alcohol testing improved road safety. This statistic was lower for drugged driving, although over 60% of respondents thought it was a significant road safety issue and disagreed with the statement that random roadside drug testing would not improve road safety. Although a large majority of the respondents (> 60%) thought that people were likely to be caught by police for drinking and driving, only 26% of participants thought people were likely to get caught for drugged driving. There was also support from the respondents for more police time and resources to be directed towards enforcing drugged driving laws. Another aspect of the study focused on the feasibility of an alternative approach to studying drugged driving which was not reliant on participant self-reporting. This was the analysis of blood or saliva samples from drivers involved in a crash. In New Zealand, several reports have been published based on drug levels found in blood samples of dead and injured drivers analysed for blood alcohol testing, but the sample sizes have been relatively small and limited to blood collected for evidential purposes. It is clear, however, that analysis of a larger sample of drivers involved in crashes would provide a more accurate picture of the extent (and impact) of drugged driving in New Zealand. Consultation was undertaken with staff from Waikato District Health Boards, the Institute of Environmental Science and Research, the Ministry of Transport and the Waikato Police Traffic and Alcohol group to explore the feasibility of carrying out additional toxicological analyses on blood samples routinely drawn from trauma patients admitted as a result of a car crash. Currently it would not be possible to carry out additional analyses on the blood samples already drawn, but an additional sample (of blood or saliva) could be taken close to the time of the crash and sent to an external laboratory (the Institute of Environmental Science and Research) for analyses. Approval would be required from the Waikato District Health Board and the National Health and Disability Ethics Committee. The implications from the present study suggest that public education could include the effects of combined drug use, in particular the combination of alcohol and prescription medication. Drivers need to be aware that any amount of alcohol (even below the legal drink driving limit) in combination with prescription medication may affect their driving ability and increase their risk of being involved in a crash. One strategy would be to encourage people to plan when they take their medication in relation to when they need to drive and to continue to raise awareness of the fact that we are not good at judging our own levels of impairment. (Author/publisher)
Samenvatting