4.1. Performance
User performance while using an AR instruction method was assessed against the paper instruction method using total training time. Maintenance training times varied significantly between tasks, with a significant increase from low-demanding to high-demanding regardless of instruction method type (i.e., a 50% increase). The training time for the high-demanding task was significantly higher than the low-demanding task in the AR-based instruction method (24.48 vs. 13.30 min) and the paper-based instruction method (28.76 vs. 13.36 min). Using AR instructions, the time was saved by 0.45% for the low-demanding task and 14.94% for the high-demanding task as compared to paper instructions. The study’s findings revealed that using AR-based instruction during high-demanding tasks significantly speeds up maintenance training when compared to paper-based instruction. It could be argued that paper-based instruction for this highly demanding task is time-consuming as it requires browsing papers and extracting different features. In contrast, the introduced AR-based instruction provides different functionalities that can be presented on demand (i.e., virtual and real contents). On the other hand, no advantage in training time was observed while using AR for the low-difficulty task with a small number of task steps. Thus, AR instructions showed great improvement in training time as the difficulty level increased.The findings of this study are in line with those in existing studies [