## 2 Materials and Methods  
This systematic review followed the guidelines of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) [66]. To achieve its objectives the following research questions were formulated:  
* RQ1--What are the relevant smart city IT-based applications to facilitate the mobility of older adults? * RQ2--What type of data (i.e., sensors and city data) are being used to support the proposed applications? * RQ3--What are the maturity levels of the solutions being reported? * RQ4--What are the barriers for the dissemination of the solutions that were identified? Boolean queries were prepared to include all the articles that have in their titles, abstract or keywords a reference to smart city (i.e., one of the following expressions 'Smart City', 'Smartcity', 'Smart-city', 'Smart Cities', 'Smartcities' or 'Smart-cities') together with at least one of the following terms: 'Elderly', 'Older', 'Senior', 'Ageing' or 'Ageing'. The resources considered to be searched were two general databases, Web of Science and Scopus, and one specific technological database, IEEE Xplore. The literature search was concluded in April 2021. As inclusion criterion, the authors aimed to include all the articles that reported evidence of explicit use of IT-based application requiring smart cities' infrastructures to facilitate the mobility of older adults. Considering the exclusion criteria, the authors aimed to exclude all the articles not published in English, without abstract or without access to full text. Furthermore, the authors also aimed to exclude all the articles that reported overviews, reviews and applica \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Topic** & **Reference** & **Title** & **Year** \\ \hline \multirow{3}{*}{Mobility} & [53] & _Emerging big data sources for public transport_ & \\  & _planning: a systematic review on current state of art_ & 2019 \\  & _and future research directions._ & \\  & [54] & _Smart parking: a literature review from the_ & \\  & [55] & _the technological perspective._ & \\  & [56] & _The quality of smart mobility: a systematic review._ & 2020 \\  & [56] & _A systematic review of urban navigation systems for_ & 2021 \\  & [57] & _Enabling technologies for urban smart mobility: recent_ & 2021 \\  & [58] & _Trends, opportunities and challenges._ & 2021 \\  & [58] & _Barriers and risks of Mobility-as-a-Service (MaaS)_ & 2021 \\  & & _adoption in cities: a systematic review of the literature._ & 2021 \\ \hline \multirow{3}{*}{Age-friendly initiatives} & [59] & _Implementation of age-friendly initiatives in smart_ & \\  & & _cities: probing the barriers through a_ & 2020 \\  & [60] & _Smart and age-friendly cities in Romania: an overview_ & 2020 \\  & & _of public policy and practice._ & 2020 \\  & & _Smart and age-friendly cities in Russia: an_ & \\  & [61] & _exploratory study of attitudes, perceptions, quality of life and health information needs._ & 2020 \\  & & _Smart and age-friendly communities in Poland: an_ & \\  & [62] & _analysis of institutional and individual conditions for_ & \\  & & _a new concept of smart development of ageing_ & 2020 \\  & & _communities._ & 2020 \\  & [63] & _Quality of life framework for personalised ageing: a_ & \\  & & _systematic review of ICT solutions._ & 2020 \\  & [64] & _The role of mobility digital ecosystems for age-friendly_ & 2020 \\  & & _urban public transport: a narrative literature review._ & 2020 \\  & [65] & _Use of connected technologies to assess barriers and_ & \\  & & _stressors for age and disability-friendly communities._ & 2021 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: State-of-the-art reviews related to smart city mobility and age-friendly initiatives. tions that do not explicitly require smart cities' infrastructures, or that were not relevant for the specific aim of this study. The selection of the articles was performed in three steps:  
* First, the authors removed the duplicates and the articles without abstract.