# Applications of Digital Twin across Industries: A Review
## 8 Smart City  
A smart city is the one that utilizes information and communication technology to efficiently run it, by sensing, analyzing, and integrating the key information of core systems and thus making intelligent decisions to the needs of the city, which include livelihood, environment, public safety, city services, industrial/commercial activities, etc., [126]. Insmart cities, DTs have found their application in urban planning also, to improve the quality of life of people. One such example is Carson City in Nevada, USA. Carson City Public Works Department developed a DT for the management of their water supply, which resulted in supplying water to 50,000 citizens of the city efficiently and a 15% reduction in operational hours [127]. Using a DT for planning and decision making can lead to cities that are more economically, environmentally, and socially sustainable. In 2018, the National Research Foundation (NRF) of Singapore created a 'Virtual Singapore', combining 3D maps, city models, and a data platform with fine details including texture, building materials, geometry, and components of facilities, etc. NRF believes that Virtual Singapore will be beneficial not only to the government, but also to its citizens, business owners, and other research communities by acting as a testbed for new ideas and by providing information that will help in the decision-making process, as well as in resource planning and management. It can also be used to improve the accessibility of a specific area and simulate emergency situations [128]. Another city adding to this list is Amaravati, India. The DT of the city is being designed for a population of 3.5 million people costing USD 6.5 billion. The project is going to cover an area of 217 km\({}^{2}\), which includes 134 km of the metro network, 316 km of main roads, over 100 hospitals and schools, 40 colleges, 3 universities, and 3 state government buildings [129]. According to Cityzenith, the company responsible for developing the DT of the city, Amaravati will be one of the top three digitally advanced cities in the world on completion. Having cities on digital platforms will allow their stakeholders to monitor the construction progress in real-time, the environment and overall wellness of the city, mobility and traffic, the microclimate and climate change, etc. Moreover, it will serve as a portal to all citizens for all government information, notifications, forms, and applications [130]. A similar project has been launched by the government of Victoria, Australia, to create a DT of a 480 hectares area called Fishermens Bend near Melbourne, Australia. The project will have real-time data visualization of public transport and building occupancy, tools for planning analysis and analytics, traffic flow predictions, power and water usage forecasts, etc., [131]. The DT of a smart city can be used for disaster management or emergency response plans [132; 133]. The DT of the Docklands area in Dublin, Ireland, developed by [PERSON] et al. [134], was fed with the rainfall amount and river levels data to predict when flooding could occur, which could be used to alert the citizens of possible floods. In smart cities where flooding has been identified as a problem, historical data of the city can be used for creating a longer-term flood prevention mechanism, planning city skyline, or for large-scale projects such as introducing water storage areas or diverting rivers accordingly. A DT can change the way we look at our cities and living spaces. It can help authorities in resource allocation, urban planning, and sustainable development. It can also give urban designers as well as architects, engineers, constructors, property owners, and citizens an opportunity to study and analyze the city's infrastructure in different scenarios and assess any future risks, thus improving the overall performance of a city, its infrastructure, processes, and services [135].