Work Package 1 – Methodology & Research
Work Package-leader: Anja Knoche, Federal Highway Research Institute, Germany
Within the Integrated Project different methodologies (for example epidemiological, experimental research) will be applied using a wide variety of observational parameters, for example experimental variables measuring performance and activation state, accident data based on case control studies or from medical records, experimental on-road data under varying conditions. In order to combine the results from all different studies conducted in DRUID, a theoretical framework and an integration methodology will be established using the results of alcohol research as reference base.
Why will we use the results of alcohol research as reference base? For alcohol, a huge body of empirical results and theoretical considerations has been accumulated over the past 100 years. Additionally, the effects of different legal thresholds on driving safety are well understood. Once the model established by using alcohol as a reference substance, the model can be applied for all other substances under study. Additionally, a procedure will be developed which allows to combine the results from different studies into a quantitative estimate of impairing effects on driving.
Beside the conduction of experimental research the relevant literature about the effects of those substances on human performance and driving behaviour will be evaluated for their impact on traffic safety. This meta-analysis is weighted for methodological standards of studies and for a quantitative estimation of driving related skill-parameters (for example attention, reaction time, lane keeping). The results of the meta-analysis will be included in the threshold calculation for psychoactive substances together with the outcome of the experimental and epidemiological research.
A total of 15 experimental studies will be designed to assess the effects of drugs, alcohol and medicines on driving performance under experimental, placebo-controlled conditions. The studies will include drugs and medicines that have been frequently implied in epidemiological research to potentially increase crash risk; as well as "novel" or "recent" drugs which are supposed to affect driving performance but where not enough knowledge exists. The studies will be conducted with the psychoactive substances alone and in combination. To preserve as much as possible the driver’s mobility under medical treatment the experimental studies will compare the driver fitness of ill persons which have to take their medicines with and without these medical treatments.
Driving performance will be assessed using psychomotor and cognitive tests measuring skills related to driving, driving simulators and on-road driving tests. On-the-road tests will include combined city and highway driving tests in order to measure performance under varying workload conditions, and will involve the fundamental aspects of driver vehicle interactions. Tests in advanced driving simulators will be developed to assess similar fundamental driving skills, but in addition include tests of reactions on traffic signals, compliance with traffic control devices, risk taking behaviour and situation awareness as well. By using the same basic parameters in on-the-road and simulator studies (for example reaction time in a sudden event) a comparison of their results will be guarantied. In the current proposal, the effects of stimulants and hypnotics will be assessed both in driving simulators and on-the-road driving tests in order to cross-validate both experimental approaches. In order to give a comparable data base for the saliva samples from epidemiological studies all experimental studies will use blood and saliva samples of each participant for analysing.
Based on the results of epidemiological research, odds ratios regarding the accident risk for various drugs and medicines can be computed for different substance concentrations and thus contribute to setting concentration thresholds. The results of the experimental research conducted within Task 1.2 will be used in order to proof the risk calculations conducted in work package 2 "epidemiological studies".
Taking into account the consumption-driving patterns of substance users, the prevalence of substances among road users in general traffic and in accident causation, the experimental studies results and the results of relative risk calculation from epidemiological studies will be integrated in the established theoretical framework. Recommendations for thresholds for the substances under investigation as a proper indicator of impaired driving comparable to the promille thresholds for alcohol (alcohol per se limits) will be formulated according to the results.
The last step in work package 1 will be a synopsis of the different results and the knowledge which was collected and summarised in this IP concerning the recommendation for further regulations. This synopsis also implies a comparison of the results with respect to the different legal conditions in the European Member States. This includes the prevalence of substances as well as the adequacy of recommended thresholds. This analysis will take into account the results of work package 6 where the legal regulations in the different countries are outlined.
A literature review about the rationale of defining thresholds methodology to extract and define thresholds from empirical findings and the demonstration of the functions of thresholds within the legal system of a country will be demonstrated. There do exist two alternatives: a zero-tolerance approach and an approach of a controlled acceptance. Both issues must be discussed on the base of empirical findings and with respect to models in criminology. Also, the relevant literature about the effects of raising or lowering thresholds must be analysed. In case of zero-tolerance legislation analytical thresholds for psychoactive substances have to be defined. These analytical thresholds will be recommended by a round table of experts.
The empirical body of findings in this IP has to be analysed with respect to those methodological and practical considerations. The result must be a well-founded set of alternatives for setting thresholds which can serve as a rational base for legislative actions, taking into account to preserve as much as possible the drivers mobility under medical treatment.
A special role in this context play subsitute substances (for example Methadone) and drugs used as medicines (for example Cannabis, Morphine). Recommendations for patients using such substances will be worked out based on the existing knowledge. These recommendations will give an important input for the strategies of conditional withdrawal in Task 6.2.