Cognitive load and task switching in drivers: Implications for road safety in semi-autonomous vehicles

• Cognitive psychology principles are used to explain task switching during driving. • Cognitive overload and underload impair subsequent driving performance. • Attentional switch costs following a takeover response can persist for 5 min. • Suggestions are given for improving the safety of Level 3 automated driving. As the semi-automation of motor vehicles advances, the prevalence of multitasking and task switching while driving has increased. In the next phase, known as conditional automated driving (level 3 automation), drivers will be able to fully engage in distracting tasks, yet they must be prepared to promptly resume control of the vehicle and maintain safe driving if requested to by the vehicle. In such situations, the driver’s ability to flawlessly switch between the distracting task and the driving task becomes vitally important. This narrative review discusses conditional automated driving within the framework of cognitive psychology concepts of attention and task switching. Delayed reaction time and deteriorated driving performance are attributed to cognitive overload and switch cost. Factors that contribute to driving switch cost are identified and categorized, and several road safety concerns are raised, including: i) switch cost may last for between 20 s to 5 min; ii) inexperienced drivers may be unable to adequately control the vehicle after resuming manual control; and iii) low- and high-intensity non-driving tasks have a greater impact on takeover performance. To minimise the risk to road safety, suggestions have been provided to vehicle manufacturers, road users and regulatory authorities.