Background. This article deals with powered wheelchair (PW) simulators. In any application of simulation (learning, medical prescription, experimentation of new features, etc.) it is necessary to define driving performance criteria. The aim of this work is to validate a new performance index for PW driving analysis. Methods. The validation was carried out in two stages. First, we modelled the human-machine system consisting of the pilot and the PW with the OPCM model (Optimal Preview Control Model) and we deduced the importance of the preview time or its equivalent, the preview distance . Experiments on a panel of 15 healthy subjects were carried out on the 3D simulator ViEW (Virtual Electrical Wheelchair) associated with an eye-tracker system and allowed to validate this modelling. In the second stage, the healthy panel was separated into two skill-level groups (accustomed/novice). Results. The experimental results showed that the parameter is representative of the driving quality: accustomed drivers get greater values of than the novice users during the driving. To illustrate this assertion, we conclude by a case study conducted on five subjects with motor disabilities. Conclusion. This work showed that allows to differentiate accustomed users from the novice ones using a test on healthy subjects. A second test on subjects with disabilities showed that this indicator can be used for analysing their abilities to drive the PW.