To optimize the use of partially autonomous vehicles, it is necessary to develop an understanding of the interactions between these vehicles and their operators. This research investigates the relationship between level of partial autonomy and operator abilities using a web-based virtual reality study. In this study participants took part in a virtual drive where they were required to perform all or part of the driving task in one of five possible autonomy conditions while responding to sudden emergency road events. Participants also took part in a simultaneous communications console task to include an element of multitasking. Situation awareness was measured using real-time probes based on the Situation Awareness Global Assessment Technique (SAGAT) as well as the Situation Awareness Rating Technique (SART). Cognitive Load was measured using the NASA Task Load Index (NASA-TLX) and an adapted version of the SOS Scale. Other measured factors included multiple indicators of driving performance and secondary task performance. Results indicate a relationship between performance and autonomy level.