The impact of having a 15-minute break with and without consuming an energy drink on prolonged simulated highway driving

Abstract

Introduction: Driving a car may be negatively affected by driver sleepiness. This is especially seen under monotonous conditions such as prolonged highway driving. This study examined the effects of energy drink (ED) on simulated highway driving. Materials and methods: In a double blind crossover study, N = 21 healthy volunteers performed a 4-hour driving test in the STISIM driving simulator. After 2 hours driving, a 15-minute break was scheduled in two of the three conditions. During the break subjects consumed either 250 ml ED (Red Bull) or a placebo drink (Red Bull without caffeine (80 mg), glucuronolactone, taurine and B-vitamins). Subjects were instructed to drive with a steady lateral position while maintaining a constant speed of 95 km/h. The primary outcome measure was the number of lapses. A lapse is considered to be a short period of inattention and is defined by a deviation from the mean lateral position for >100 cm for 8 seconds or more. Results: No significant differences were observed between the ED, placebo, and continuous driving (9.2, 9.9, 12.5 lapses) in hour 2. In hour 3, significantly fewer lapses were observed after consuming ED versus continued driving (4.3 versus 9.5 lapses, p = 0.020), and having a break and a placebo drink produced a non-significant reduction in the number of lapses (7.4 lapses, p = 0.365). In hour 4 after consuming ED, again significantly fewer lapses were observed when compared with continued driving (6.2 versus 9.4 lapses, p = 0.014). After placebo, the number of lapses in the 4th hour were similar to those observed in the 2nd hour of driving (9.9 versus 9.9 lapses, p = 0.456). In hour 3, the improvement by consuming ED relative to placebo did not reach significance (p = 0.097). In hour 4, consuming ED was significantly more effective in reducing the number of lapses than having a break only (p = 0.034). Conclusion: A 15-minute break in combination with consuming an energy drink significantly reduces the number of lapses during prolonged simulated highway driving.