Individual differences and their impact on the safety and the efficiency of human-wheelchair systems

Objective: The extent to which individual differences in fine motor abilities impact indoor safety and efficiency of human-wheelchair systems was examined. Background: To reduce the currently large number of indoor wheelchair accidents, assistance systems with a high level of automation were developed. It was proposed to adapt the wheelchair’s level of automation to the user’s ability to steer the device to avoid drawbacks of highly automated wheelchairs. The state of the art, however, lacks an empirical identification of those abilities. Method: A study with 23 participants is described. The participants drove through various sections of a course with a powered wheelchair. Repeatedly measured criteria were safety (numbers of collisions) and efficiency (times required for reaching goals). As covariates, the participants’ fine motor abilities were assessed. Results: A random coefficient modelling approach was conducted to analyse the data, which were available on two levels as course sections were nested within participants. The participants’ aiming, precision, and arm-hand speed contributed significantly to both criteria: Participants with lower fine motor abilities had more collisions and required more time for reaching goals. Conclusion: Adapting the wheelchair’s level of automation to these fine motor abilities can improve indoor safety and efficiency. In addition, the results highlight the need to further examine the impact of individual differences on the design of automation features for powered wheelchairs as well as other applications of automation. Application: The results facilitate the improvement of current wheelchair technology