A comparative analysis of mental effort on motorway and conventional road driving

The review of the different theoretical approaches explaining mental effort in the execution of tasks allows us to differentiate two effort types: task-related effort and state-related effort. Driving a vehicle is a complex task which requires both effort types made by the driver, since the aspects relating to the driving task and the driver's state play a role in determining the amount of mental effort and, therefore, of the attention resources finally used. Our research aims to determine whether or not differences appear in mental effort invested by drivers on two road types: motorway and conventional road. To that end, mental effort was analysed in a number of volunteers while driving on both types of roads. Effort was derived from two cardiovascular activity spectral measurements: the amplitude of the 0,1 Hz frequency component and an index of sympathovagal activity-calculated by means of the ratio 0,1 Hz / 0,25 Hz components-of the inter-beat interval variability, the 0,1 Hz component being a value exclusively sensitive to the task-related effort. Results show that mental effort derived from the index of sympathovagal activity was generally greater on the motorway than on the conventional road. Yet, this difference was not found for the mental effort derived from the 0,1 Hz component, suggesting that the difference found could be put down to the state-related effort and not to the task-related one.