## 4 Case Analysis: Validity Check for the Framework
Based on these analyses, it can be inferred that the frameworks for the analysis of the actual use environments and derivation of the key components of living labs are well applied to this product as a whole. Next, when it comes to the framework for prioritization, it can also be concluded that the framework is not only applicable, but also useful for the product. According to the method in Figure 5, the technological context of the product has the lowest priority, because the product does not work dependently on other products or systems. In contrast, the key elements of the other two real-use environments of the product have higher priorities when implementing in living labs for the verification process. Specifically, the road delineation by light, i.e., the major function of the product, is something that should be designed in consideration of the user demographics, because all users should be able to recognize the light while driving a car. Especially, according to previous research, human visual angle changes with age [43]. This indicates that the test method and threshold value of the luminous intensity should be confirmed, necessarily taking into account the different visual angles with ages. In a similar vein, other studies claim that drivers must be able to pay enough attention to cyclists running on the roadside [44]. In addition to the user demographics, various user activities, such as driving lanes and speed, and other drivers' situations, such as the number of cars in other lanes, are also important in designing, evaluating, and optimizing the product. For example, when evaluating the performance of the product for certification, the measured luminosity of the product must be high enough so that the sharp curve chevron can be recognized at the maximum speed limit of the road when driving in the innermost lane (i.e., user activity at the time of the product is used). The physical real-use environments of the product also have a higher priority. Particularly in the aspect of the natural environment, the fiber-optic LED pads must be designed to function in a variety of outdoor conditions such as heavy rain and high temperature in summer. Moreover, in order to optimize the product to the real-use environments including dusty areas, the dust-proof properties of the product should be designed, by considering the fact that the product is likely to be used on the roads with dirt, mountains, or deserts around it (i.e., natural environment), or on the roads adjacent to factories or construction sites (i.e., artificial environment). Lastly, it is already clear from the preceding analyses that the test methods that need verification (e.g., the luminous intensity) are highly relevant to the physical use environments, as well as the user characteristics. Taken together, these analyses above provide evidence that the framework for the prioritization also fits the real sample case well, as a useful tool. Next, the applicability of the proposed frameworks is further examined with four additional NCPs: air-ventilated welding helmets, heating curtains, IoT-based manhole tops, and floor noise level meters. The analysis results are summarized in Tables 2 and 3. For a better understanding, the key background information about the four products is provided below. Air-ventilated welding helmets are a new convergence product designed to reduce the heat increases when worn, by ventilating the inside air with external air. Despite expectations for increased user satisfaction, there are concerns that various welding fumes floating in the welding place may flow into the product through the fan. Some experts may say that the main function of a welding helmet is to protect a user's eyes from the welding lights, and that even if fumes flow inside the product, the user is protected by a dust mask. However, other experts may point out that it is necessary to develop and verify a test method and criteria to ensure that hazardous fumes do not get inside the welding helmet due to the different features (i.e., ventilation fan).