Inter and intra-individual differences in steering wheel hand positions during a simulated driving task.

This paper describes an experimental study focusing onto the way drivers use the steering wheel while performing a 2D tracking task. The stimulus during this task was a steering wheel angle signal recorded in real situations involving turns and straight lines performed at about 30 km/h. The hand positions of 20 volunteers were recorded in 6 steering scenarios involving 7 road geometries using a 3D motion capture system. The hand movement data were analysed via a descriptive/inferential procedure: each hand was considered using nine indicators - eight membership value averages linked to eight fuzzy angle windows and a frequency value related to the off steering wheel position - while the indicators were investigated using multiple correspondence analysis and non-parametric global and post-hoc tests. Results showed that inter-individual differences were larger than intra-individual differences. Considering 2 × 9 = 18 windows, the inter-individual differences mainly appeared during two main kinds of steering hand strategies: with versus without crossing hands, the latter being the most often used (17 among 20 participants). The intra-individual data showed that some drivers maintained a nearly identical strategy for all road geometries, while other drivers changed their hand position with the direction and/or maximum angle value of the turn. Practitioner Summary: Understanding hand position strategy could be used to design steering wheel assistance in relation to a driver's physical resources with a view to adapting the steering wheel to disabled drivers.