Lorazepam impairs highway driving performance more than heavy alcohol consumption

•We compared benzodiazepine (BZD) intake with blood alcohol concentration (BAC).•16 participants underwent a 2-h driving paradigm in real-world and simulated settings.•Weaving (SDLP) and inappropriate line crossings were higher in the simulator.•The SDLP increment after BZD equalled high BAC values in both real and simulated conditions.•We recommend that physicians be made more aware of BZD-related risks.

While research indicates that benzodiazepine (BZD)-like drugs impair driving performance, it remains unclear (i) how far BZDs affect lane-keeping performance, compared with alcohol and (ii) to what extent this impact can realistically be measured in a simulated environment. To clarify these issues, 16 healthy male drivers who had never previously taken BZDs underwent a randomized, crossover, double-blind, placebo-controlled driving paradigm (with the BZD lorazepam) in both real-world and simulated settings. Two lane-keeping variables, namely inappropriate line crossings (ILCs) and standard deviation of lateral position (SDLP), were recorded during the driving sessions. Analyses revealed that (i) a single lorazepam dose (2 mg given by mouth) caused higher SDLP increases than a blood alcohol concentration of above 0.05%, and that (ii) this BZD effect was amplified in the simulated driving setting, mainly for ILCs. As a consequence, we recommend that physicians be made more aware of BZD-related risks and that researchers make a clear distinction between the effects of BZD intake per se and the impact of simulated driving settings.