Vehicle control and drowsiness - VTI

13 Analysis of the mean value of the lateral positionFigure 29 shows the mean value of the lateral position for tired and alert subjectsin the “Hök” study, calculated for every five-minute period. The Y-scalerepresents the vehicles position measured from the middle line on the road to theleft side of the vehicle. The difference in lateral position between tired and alertdrivers is significant [F(1,18)=6.04, p=0.024]. As can be seen in figure 29, thetired subjects are closer to the middle line. A possible explanation is that on ahighway (which was the type of road used in the experiments), the driver thinks itis safer to drive closer to the middle line. There is a weak significance for changeof lateral position over time [F(23,414)=1.647, p=0.0313].2,52,42,3Lateral position (meters)2,22,121,91,81,7TiredAlert1,61,55 15 25 35 45 55 65 75 85 95 105 115MinutesFigure 29 Lateral position as a function of time for tired and alert subjects. TheY-scale represents the position of vehicles measured from the middle line on theroad to the left side of the vehicle.A egression analysis of mean values of the drowsiness rating and lateral positionfor tired and alert drivers was carried out. The analysis showed that there is nosignificant relationship between increasing drowsiness and increasing lateralposition. The mean values of the drowsiness rating and lateral position arecalculated for every five minutes during the two-hour drive.58 VTI meddelande 922A