Recently, the relationship between driver distraction and road safety has come strongly into focus, based on findings presented from Naturalistic Driving Studies and Field Operational Tests.

Reviews of current literature on the subject show that the available conceptual frameworks for describing the relationship between secondary task involvement and driver performance are predominantly linear and mono-dimensional, i.e. they propose a single, direct and linear correlation between secondary task engagement and reduction in driver performance. However, as research into other areas of human performance show, descriptions of a linear and/or mono-dimensional character rarely are sufficient to predict the differences between mono- and multitasking in human operators.

Transferred to automotive safety, this means that to evaluate the effects of new in-vehicle systems on driver performance, a more sophisticated framework is needed. In particular, any warning/intervention capabilities of the vehicle, the current performance capacity of the driver, and primary task demand variation all need to be added and accounted for in order to accurately assess the extent to which secondary task involvement may degrade primary task performance.

In this paper, a conceptual framework which takes these additional dimensions into account is outlined. The framework describes how driver performance capacity, the availability of active safety systems in the vehicle and the current demands from the traffic environment should be jointly considered in relation to the effects on driver performance of secondary task engagement. Based on this, general areas where improvements can be made in order to mitigate negative consequences of non-driving tasks are presented.