# Digital Twin Framework for Road Infrastructure Management
## 7 Discussion and Conclusions  
DT technology is an emerging concept that is becoming indispensable in road infrastructure management owing to its capabilities and potential. To fully harness and systematically apply DT technology within the industry, a formalized approach must be adopted. The ISO 23247 manufacturing DT standard is one of the most commonly referred standards, consisting of four parts, with Part 2: Reference Architecture being most relevant to this study. Although this standard can serve as a reference for the AEC industry until dedicated standards are developed for the built environment, its applicability is limited due to its primary focus on the manufacturing domain. Additionally, the inherent complexity of the AEC industry, characterized by multiple stakeholders and a rapidly evolving technology-driven environment, further limits its direct adoption. Nevertheless, several studies have cited and applied the ISO 23247-2 DT framework--i.e., reference architecture within the road infrastructure domain. Many researchers and scholars have also proposed their own DT framework models, often drawing from existing frameworks in manufacturing and other relevant sources. As no widely accepted standards or reference models currently exist for DT in the road infrastructure industry, particularly from a road management perspective, this research aimed to explore how existing studies address DT framework models and their proposed frameworks. To achieve this, we adopted a bottom-up approach, thoroughly examining literature related to the road infrastructure domain, including road infrastructure network management, road bridges, road tunnels, and other civil infrastructures and urban DTs. Consequently, we identified relevant DT layer structures and their key components and selected a total of 26 studies employing a DT layered approach, specifically frameworks and/or reference models in the areas of road infrastructure (eight papers), bridges (six papers), tunnels (five papers), and other civil infrastructures and urban DTs (seven papers), based on their alignment with the objectives of this study. We defined the DT layers by comparing and analyzing their definitions and functionalities across the selected studies. Based on this analysis, we derived and proposed five DT layers: the data acquisition and transmission layer; the data processing, integration, and storage layer; the data/digital modeling layer; data analytics/application layer; and the users/UI layer. Thus, this study presented the DT framework and its main components from a functional perspective, focusing on identifying and visualizing key DT functionalities derived from selected studies to inform future applications. Therefore, defining common DT layers is essential to developing a comprehensive DT framework for managing road infrastructure which could also serve as integrated network-level management of road assets. Furthermore, we compared the proposed framework with the ISO 23247-2 DT manufacturing framework (reference architecture) to enhance understanding and facilitate its practical application in the development of road DTs. In addition, the implementation scenario is discussed as a case study, illustrating how the proposed DT framework can be applied to the BMS to address existing challenges and enhance future (potential) applications. DTs and frameworks like the one proposed in this study are expected to significantly contribute to the development and application of intelligent transportation systems, especially with the rise of autonomous vehicles. They provide intelligent infrastructures that serve as foundational elements for these systems. Furthermore, this framework could facilitate the integration of smart infrastructures to develop smart cities. The proposed DT framework can be adopted for various road infrastructure DT applications throughout the asset lifecycle, guiding future DT applications in the industry and supporting standardization efforts within the domain.