Effect of driving speed on reaction time during motorway driving

Effects of driving speed (70, 90 and 110 km/h) on subsidiary auditory reaction time were studied during car driving on a motorway with a speed limit of 110 km/h. Driving distance was held constant at about 200 km. Twenty-four subjects participated in a repeated-measurement design. Reaction time was found to be slower at 70 km/h than at 110 km/h. Before and after the driving session, the subjects' simple reaction time, mood, and alertness were measured in the laboratory. No significant differential after-effects of driving speed were found on any of these measures, although subjects rated themselves as less energetic towards the end of their journey when driving at the former compared to the latter speed.