Assessing Effects of Alcohol and Medicines on Driving Performance in a Simulator Environment
Gunnar D. Jenssen, SINTEF Technology And Society, Lone-Eirin Lervåg, SINTEF Technology And Society, (more Authors Will Be Considered When Writing The Paper),
The paper will present and discuss a validated methodology for using an advanced driving simulator for assessing effects of alcohol and drugs on driving performance. In addition, implications for policies on medicines and driving will be discussed.
Driving under influence of alcohol or drugs is extremely dangerous and causes a substantial part of road traffic fatalities. This also involves prescription and over the counter medicines, that are legal, but still impair driving skills. De Gier (2005) states that a conservative estimate indicates that 10% of the adult population drives under the influence of impairing medicinal drugs, causing abouth 4500 deaths, 135.000 injuries each year in Europe. The problem is increasing with an elderly population, who expect to keep up their mobility despite an extensive use of medicines.
As for alcohol, research and large epidemiological studies has proven a strong relationship between blood ethanol concentrations (BAC) and accident risk. For other drugs and medicine, however, the knowledge on how blood drug concentration affects crash risk is sparse. This is among other factors related to the methodological difficulties with assessing drug driving and traffic safety issues. As epidemiological studies on the traffic safety effects of drugs and alcohol are rare and influenced by a number of confounding factors, experimental studies are of great importance.
A Norwegian study conducted in collaboration by SINTEF Transport Research and St. Olav University Hospital, has developed and validated a driving simulator tool for future assessment of drug effects on driving performance. The purpose of the study was to establish a driving simulator test battery sensitive to ethanol effects, and to validate the methodology by comparing driving under the influence of ethanol both on a closed-circuit test track and in the driving simulator.
A driving test scenario typical for accidents involving alcohol and sedative drugs were developed and a cross-over trial with 20 male drivers were conducted, comparing driving performance on the test track and in the driving simulator. Each subject underwent a total of six driving trials of one hour duration each; three in an instrumented vehicle on a closed-circuit test track and three in an advanced driving simulator with a driving scenario modeled as a virtual copy of the test track. The scenario consisted of narrow lanes with curves, hills, dips and straight road sections. Test subjects were titrated to BAC levels of approximately zero, 0,5 ‰ and 0,9 ‰. The study was conducted in a randomised, cross-over, single blind fashion, using placebo drinks and placebo pills as confounders. The outcome measures were standard deviation of lateral position (SDLP), mean speed, speed fluctuations, steering wheel movements, braking/acceleration, and reaction time to unexpected events. Statistical analysis were conducted, using a linear mixed model with SDLP as dependent variable, measuring BAC as covariate, and participant as random effect.
Results show that both on the test track and in the simulator, the SDLP increases significantly with higher ethanol levels in a dose dependent manner. Correlation between test track and simulator results, suggests that SDLP is a valid and sensitive measure of driving impairment under the influence of ethanol in the simulator. The results are also comparable to historical data from Dutch on-road motorway tests (Verster et al., 2004), with the effects in the present study being most pronounced in curves.
Focus of the ETC paper:
The present study has concluded that the SINTEF advanced driving simulator is a sensitive and valid tool to assess driving impairment from ethanol. The ETC paper will focus on the methodology for assessing driving impairment due to alcohol and drugs, discussing how the results from the validation study may be extended to include other sedative drugs as well, by using ethanol as a positive control. Further, the implication for national and European policies regarding medicine use and driving will be discussed.
Association for European Transport