## 5 Conclusions  
The study reported by this article aimed to review smart city applications to facilitate the mobility of older adults. Relevant application domains were identified, including requirements and development platforms, accessibility, localization, mobility assistance, health conditions monitoring, promotion of healthy lifestyles, and data analytics. The results show that there is an ongoing effort to take advantage of the smart cities' paradigm to make cities more age-friendly by facilitating the mobility of older adults, namely by using a diversity of sensing data provided by a broad range of sensors. However, issues such as user privacy, data standardization and integration, and sensors' characteristics were poorly addressed. The results also show that there is a lack of maturity of the developed applications, which constitutes a major barrier to their dissemination. Moreover, it is foreseen that the number of articles related to the topic will increase in the future, since the research effort increased over the years: the oldest articles that were included were published in 2013 and more than two-thirds of the included articles were published in the last four years. According to the study protocol (e.g., search keywords and inclusion and exclusion criteria) this review only considered the research related to smart cities' applications specifically focused on facilitating the mobility of older adults. However, older adults constitute a heterogeneous population group with different needs, life experiences, expectations, and personal factors, which means that, when needed, there are older adults able to use applications developed for the general population. In this respect, one of the limitations of this study is related to the fact that there are other smart cities' applications and services developed for the general population that can be used by older adults to facilitate their mobility (e.g., pedestrian mobility [102], multi-modal routes' support [103], smart parking [54], traffic management [104], assistance to drivers [105; 106], intelligent transport systems [25; 106; 105], or mobility as a service [38; 58]). Moreover, it should be noted that this review did not consider other possible studies aiming to facilitate the mobility of older adults without being supported in smart city infrastructures, nor articles whose primary focus was not the use of IT (e.g., [107]). Additionally, the review did not consider articles published after March 2021. Moreover, is always possible to point out limitations about both the chosen keywords and the databases that were used in the research. Likewise, since most articles were published in conference proceedings, there will certainly be similar articles that have not been included because they were presented in non-indexed conferences. It should also be noted that the grey literature was not considered in this review and that this can be seen as a gap of some significance. Despite these limitations, in methodological terms, the authors tried to follow rigorous procedures for the articles' selection and data extraction, so that the results are relevant for identifying IT-based applications requiring smart cities' infrastructures to facilitate the mobility of older adults, which may contribute to future developments. Based on the findings of this systematic literature review, it is possible to conclude that most of the identified studies supported older adults' requirements, which means that there is a trend in the research of practical solutions. However, only one article reported an experimental set-up to assess the proposal solution in a real-life scenario. The remainder articles proposed concepts, architectures, and proof-of-concept prototypes. Four proof-of-concept prototypes were validated by older adults, but the respective experimental designs exhibit limitations. The technological solutions should respond to user needs and not the other way around.