# Leveraging Digital Twin Technology for Sustainable and Efficient Public Transportation
## 3 Challenges and Limitations of Digital Twins
### High Costs and Infrastructural Requirements  
High costs and infrastructural requirements are also technical challenges that can arise in the process of implementing DT technology. Digital twins can create better fleet management, optimize routing, and enhance maintenance schedules. This can be beneficial to agencies as well as the public transport used in the long run. However, the initial investment required can prevent many organizations from initiating DT technology. A study highlights energy efficiency and reduced operational costs of DT implementation but also mentions that the upfront financial commitment is an inconvenience [78]. Apart from initial setup costs to adopt DTs in bus transportation, ongoing maintenance and operational expenses should also be considered. Regular updates to not only the software but also hardware, along with personnel training/management, add to the overall operating costs [33]. In one study, the authors mention that state Departments of Transportation (DOTs) face significant challenges in managing multiple assets across extensive networks. Since integration requires investment in both technology and training, many transportation agencies can be discouraged [66]. Proper functioning of DTs requires a solid technological foundation that includes advanced sensors, data analytics, and communication systems all working with each other. The bus and transit infrastructure relies on the seamless integration of these components. Using Internet of Things (IoT) devices is essential for data collection and real-time monitoring of bus fleets, but this can be costly and require significant infrastructural upgrades. For example, using networks such as 5G/6G can increase the costs associated with implementing digital twins in transportation systems [33; 60]. Successful implementation of DTs in bus transportation systems relies on managing and analyzing the large amounts of data produced in real time. Handling data from multiple sources in different formats requires advanced data analysis tools and strong systems to ensure the data are accurate and reliable. However, developing and maintaining these systems can be expensive, especially for smaller transit agencies [80]. The complexity of digital twins also requires a deep understanding of how transportation systems work as a whole. Without a clear framework to connect all parts of the transportation network, the potential benefits of digital twins might not be fully realized. As a result, transportation agencies require skilled professionals to manage and interpret the massive amounts of data generated by digital twins, adding another layer of difficulty to their implementation [61]  
Some transit agencies that operate on limited budgets can consider these technological and skilled manpower requirements as financial burdens. Another concern is the high computational cost associated with simulation and modeling of DT environments. The authors of one study discussed the impracticality of widespread DT application because of associated computational expenses. Another study indicates that the aging and deteriorating infrastructure can pose problems with effective management. Since the systems require up-to-date and real-time information to perform optimally, advanced computational resources are required for ideal operation conditions [101,109]. The need for extensive infrastructure includes not only the physical assets on its own but also the underlying data management systems for a DT framework. One study points out the multiple stages of DT implementation where the technology involved and its integration into the existing systems are carefully considered. The increase in the complexity of these systems will lead to increased operational costs to ensure that the organizational infrastructure can support the continuous data flow and processing demands of digital twins [110]. In conclusion, DT technology has the potential to improve bus transportation systems, but it also comes with significant challenges.