The relationship between driver distraction and mental workload

Driver distraction and mental workload are two constructs that are closely related, but which are affected by different aspects of the driving situation and may also have different effects on driving performance. This chapter introduces the concept of latent driver distraction, a form of driver distraction that does not materialise in measurably unsafe driving behaviour, but that does impair being able to respond adequately to upcoming safety-critical situations. It proposes using one of the measurement tools for mental workload as an indication of latent driver distraction. It further raises the issue of evidence for increased mental workload being used often as a direct indication of all types of driver distraction. However, measurements should focus on the type of driver distraction that is measured, instead of translating an increase in one of the constructs into a supposed increase in the other construct. The relationship between mental workload and driver distraction is made explicit.