To ensure transferability of driving simulator-based user trials (where motion sickness onset is likely) it is important to understand if motion sickness affects human performance and therefore user trial data validity. 51 participants had their task performance ability measured in six defined categories (including physical, cognitive, visual and the intersections of each) both before and after a driving simulator exposure. Their motion sickness state was compared to their change in task completion scores across the six areas. Findings revealed that motion sickness had a significant effect on cognitive performance, physical performance, physical-visual performance and physical-cognitive performance. There was no gender effect on motion sickness severity, but it did affect participant dropout, where female nausea was a significant effector. Age had no effect on motion sickness onset and other findings are also discussed. Conclusions from this research aid in the understanding of simulator-based user trial data validity.