**5. Conclusions**

Sensor and IoT technologies are acquiring ever-increasing importance in the techno-spatial context by collecting, processing, analyzing, and integrating large amount of data to improve the healthy functioning of our cities. In this regard, the importance of the corresponding urban assessment tools is evidenced by the vast investment made by technology giants, such as Cisco, Google, Microsoft, Ericsson, Alibaba, Oracle, in prototype sensor cities. These initiatives are helping cities, such as Toronto, Valencia, Dallas, Singapore, Kansas City, Hamburg, Shenzhen, Adelaide, Dublin, integrate IoT and related applications for big data, and actively engaging in city sensor development. The sensing city model allows policymakers to benefit from big data and urban analytics to improve urban policies, services, and operations.

The purpose of this paper is to explore and integrate di fferent sensor cities taken as case studies consistent with the research demand and to discuss technological solutions (e.g., sensors, devices, IoT, AI, platforms, digital infrastructures, computer models, ICTs), emphasizing the economic, social and environmental benefits of their practical application. Hence, the technological applications enabled by the IoT and ICTs in general have the potential to improve daily urban activities, providing a series of opportunities concerning urban dimensions such as governance, economy, environment, mobility, people and life. In this perspective, the social, environmental and economic challenges arising from the use of these tools have been explained. The study finds that disruptive urban technologies not only promote highly e fficient and computerized urban processes and e fficiency, but also improve the understanding of planning, monitoring and analysis of the performance of sensor cities by increasing awareness of citizens, businesses, local authorities, and so on.

The framework of sensor cities (see Figure 2) illustrates and defines the process of detection, collection, processing, analysis of urban data up to their transformation into information necessary for urban policymakers. In this regard, the use of IoT platforms equipped with systems, devices, sensors, algorithms, platforms, models, and so on provides a complete and exhaustive view of the future trends of urban performance measurement methodologies. Furthermore, these methodologies and approaches give rise to some important issues such as data quality and integrity, cyber security, digital data and information ethics, and regulations. These are among the critical issues that prospective research must tackle.

To recap the findings and conclude the paper, we list the following highlights of the study: (a) The proposed framework improves the understanding of the cities' progress towards becoming sensing localities to address rising issues effectively and efficiently; (b) Achieving a truly smart urbanism requires continuous monitoring trough urban platforms and dashboards; (c) The data-driven approach highlights a multitude of challenges related to urban governance; (d) Urban dashboards improve citizen accountability and awareness on urban issues, and; (e) Data security, quality, integration and stakeholders must be involved in the urban sensor strategy.

**Author Contributions:** G.D. designed and supervised the study, and finalized the manuscript. G.I., P.L., W.L. and T.Y. contributed to the write-up of the manuscript, and improved the rigor, relevance, and reach of the study. G.D. and G.I. prepared the first draft of the manuscript and assisted in data collection. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research received no external funding.

**Acknowledgments:** This research did not receive any specific gran<sup>t</sup> from funding agencies in the public, commercial, or not-for-profit sectors. The authors thank the managing editor and anonymous referees for their invaluable comments on an earlier version of the manuscript.

**Conflicts of Interest:** The authors declare no conflict of interest.


**Table A1.** Sensor city projects of high-tech companies investigated in this study (source: authors).

**Appendix A**
