This study examined the effect of different levels of caffeine and glucose on driver fatigue. The experiment was conducted using the TRL advanced full-mission driving simulator and provided a range of realistic traffic scenarios. 48 experienced drivers aged between 25 and 50 participated in this study. The sample was split evenly by gender. The study employed a double-blind, placebo controlled, repeated measures design. The three experimental conditions were: (1) Control drink (330ml, taste matched to energy drinks), (2) Level 1 energy drink (330ml, 60g glucose and 25mg caffeine), (3) Level 2 energy drink (330ml, 60g glucose and 40mg caffeine). These drinks were formulated in order to taste and appear the same in all conditions, the only difference being the caffeine and glucose dose. All participants were tested during the post lunch dip where natural alertness is at a low. Overall the results indicate an improvement in driving performance (lane keeping, reaction time and following performance) after drinking the level 2 drink (containing 40 mg caffeine and 60g glucose) compared to the control drink. Some measures also showed a slight improvement with the level 1 drink (containing 25 mg caffeine and 60g glucose).

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