# Digital Twin Framework for Road Infrastructure Management
## 3 Digital Twins in the Road Infrastructure Industry
### DT Standards Relevant to the Road Infrastructure Industry  
Several principal standard-developing organizations, such as the International Organization for Standardization (ISO), International Electrotechnical Commission (IEC), the International Telecommunication Union, and the Institute of Electrical and Electronics Engineers (IEEE), play a key role in shaping DT-related standards. [PERSON] et al. [13] reviewed the current landscape of DT standards developed by these major organizations. Their review was structured around a five-dimensional DT framework comprising a physical entity, virtual entity, connection, DT data, and services. The authors also examined associated challenges and outlined future directions for standard development. The study concluded that although standardization efforts are underway, most standards remain in their early stages, having only been initiated in recent years due to the relatively immature application of DTs. [PERSON] et al. [20] proposed an interoperable DT framework based on the IEEE standards, encompassing layers from the physical level to visualization, to support DT development. They categorized existing concepts and standards under physical sensors and actuators, communication, frameworks, security, cloud computing, visualization and simulation, and reference architecture models. Similarly, [PERSON] et al. [21] assessed DT-related standards established by major standard-developing organizations, focusing on areas such as communication, interoperability, security, quality, user interaction, and engineering. They identified a connection between these existing standards and their platform, Change2 Twin. Recently, the ISO and IEC jointly developed two standards: ISO/IEC 30173 (Digital Twin Concepts and Terminology) [22] and ISO/IEC 30172 (Digital Twin Use Cases) [23]. ISO/IEC 30173 defines terminology related to the data, models, performance, and applications of DTs. It also presents core concepts such as DT applications, systems, life-cycle processes, application types, functional views, and stakeholder roles. In contrast, ISO/IEC 30172 outlines representative use cases of DTs across various sectors, including smart manufacturing, smart cities, smart buildings, and smart energy systems, using descriptive narratives supported by illustrations or diagrams. Furthermore, upcoming ISO/IEC standards such as DT Maturity (PWI JTC1-SC41-7 DT) and DT Reference Architecture (PWI JTC1-SC41-5 DT), currently under development, are expected to contribute significantly to future DT standardization efforts [18]. Conversely, the ISO 23247 series (Automation Systems and Integration--Digital Twin Manufacturing Framework) provides a structured framework to guide the development and implementation of DTs in the manufacturing sector. This framework offers standardized guidelines and methods for creating DTs and is divided into four parts: (1) overview and general principles; (2) reference architecture; (3) digital representation of manufacturing elements; and (4) information exchange [24]. * ISO 23247-1: Overview and general principles--Outlines general principles and requirements for developing DTs in manufacturing;* ISO 23247-2: Reference architecture--Defines a reference architecture with functional views;
* ISO 23247-3: Digital representation of manufacturing elements--Specifies basic information attributes for observable manufacturing elements;
* ISO 23247-4: Information exchange--Describes technical requirements for information exchange among entities within the reference architecture. ISO 23247-2 provides guidelines for a DT reference model tailored to manufacturing (Figure 3). This model comprises four domains: the observable manufacturing domain (OMD), device communication domain, DT domain, and user domain. The OMD represents the physical asset, which is monitored by and interacts with the device communication domain. It includes elements such as personnel, equipment, material, processes, products, facilities, and the environment.