Magnus Hjälmdahl

The alerting effect of hitting a rumble strip—A simulator study with sleepy drivers

A moving base driving simulator experiment was carried out in order to investigate the effects of milled rumble strips on driver fatigue. There were rumble strips both at the edge line and centre line. Four different physical designs of milled rumble strips (yielding noise values from 1.5 to 16 dBA) and two placements on shoulder were used in the experiment. Sound and vibrations from real milled rumble strips were reproduced in the simulator. In total 35 regular shift workers drove during the morning hours after a full night shift. The main results showed an increase in sleepiness indicators (EEG alpha/theta activity, eye closure duration, standard deviation of lateral position, subjective sleepiness) from start to before hitting the rumble strip, an alerting effect in most parameters (not subjective sleepiness) after hitting the strip. The alertness enhancing effect was, however, short and the sleepiness signs returned 5 min after the rumble strip hit. Essentially no effects were seen due to type of strip. It was concluded that various aspects of sleepiness are increased before hitting a rumble strip and that the effect is very short-lived. Type of strip, as used in the present study did not have any effect.

Effects of d-amphetamine on simulated driving performance before and after sleep deprivation

RationaleStimulant drugs are commonly abused and also used to promote wakefulness, yet their effects on driving performance during sleep deprivation have not been thoroughly researched in experimental studies.ObjectivesThe aims were to assess the effects on fundamental driving parameters during simulated driving of two doses of d-amphetamine and further to assess the interaction between d-amphetamine and sleep deprivation.MethodsA double-blind, placebo-controlled experiment including 18 healthy male volunteers was conducted.ResultsThe participants felt more alert when taking a dose of d-amphetamine than when taking placebo, and the effect was stronger for the higher dose. However, the data did not show any evidence that taking d-amphetamine prevented the subjects from becoming successively sleepier during the night. A significant main effect of the dose was found for three out of the five primary indicators where the lower dose led to improved driving. These indicators were crossing-car reaction time, and coherence and delay from a car-following event. Regarding sleep deprivation, a main effect was found for four of the primary indicators and three of the secondary indicators. The results showed overall impaired driving with respect to standard deviation of lateral position and delay in reaction time when the sleep-deprived conditions were compared to the alert condition. We found no interactions between dose and sleep deprivation for any of the performance indicators.ConclusionsOur results suggest that administration of d-amphetamine does not compensate for impairment of driving due to fatigue. The positive effects of 10xa0mg were not further improved or even sustained when increasing the dose to 40xa0mg.