## 3 Results and Discussion
### Scientific Mapping
#### 3.2.7 Cost and Time Savings for Redesign  
When compared to the conventional review process of physical prototypes, the most frequently noted advantages of virtual reality are its cost and time savings. According to the research analyzed, industries may employ virtual prototypes to save money [43; 46; 48], minimize redesign time, and expedite time-to-market. Figure 7: Design review on a screen and a VR-based process [16]. Prototyping is an essential step in the product development process. However, after building a product model, testing its design and functionality requires time and money. In this context, a virtual prototyping system based on virtual reality technology has the potential to overcome these shortcomings [48]. The authors of [54] also describe the benefits of lowering the time for product design reviews and the amount of design and engineering design changes, as well as reducing time-to-market and optimizing costs. Immersion in virtual reality may result in cost savings as well as better and/or quicker design review processes. Because physical prototypes and mock-ups may be replaced by their virtual counterparts, virtual reality improves design verifications and the review process, which might contribute to cost savings for manufacturers [13, 19]. In [46], it is claimed that the principle of \"simultaneous engineering\", in which elements are designed and tested virtually concurrently with vehicle development, is achievable with, and potentially strengthened by, the use of virtual reality [46]. The authors use the automotive industry as an example to demonstrate that a type of control could be created early and parallel to the development of a new car model and tested within a virtual car model worldwide. Therefore, the cost of redesigning a model can be reduced if the type of control can be changed in the course of development. This capability enables creative departments to produce and test novel concepts without disrupting the conventional flow of product development. Products in development may benefit from rapid design updates, which save significant time and costs. Virtual reality allows therefore a novel, concrete, and resource-saving design evaluation method with significant application potential, since designers only need to produce the models that need to be tested, which greatly reduces time and costs [48]. Instant feedback and design modification could further improve product quality by making it possible to detect issues at an earlier stage [55]. In [54], the possibility of anticipating potential problems and design changes and having precise feedback about human-machine interactions thanks to the virtual simulation, before products are produced, is discussed. One study [55] focused on the cost savings associated with reduced travel frequencies, since virtual reality allows the replacement of physical review meetings and interaction for immersive technical discussions. A frequent worry when using virtual-reality-based prototypes is whether the correlation with conventional review and testing methods is maintained, as well as the degree of accuracy for usability testing. The reviewed studies indicate that virtual-reality prototypes do not compromise correlation, i.e., virtual-reality-based usability testing applies to the same degree and may provide results equal to conventional testing with physical prototypes. Several studies [48, 51, 66] reported that virtual reality usability testing has a significant connection with physical testing in terms of the metrics collected. The variance of quantitative data, such as operation errors and the time spent completing tasks, was statistically analyzed, and their correlations were validated and reported with sufficient correlational data between physical and virtual prototype testing outcomes.