# Digital Twin Framework for Road Infrastructure Management
## 4 Digital Twin Framework for Road Infrastructure Management
### Proposed Digital Twin Framework for Road Infrastructure Management
#### 4.3.5 Users/User Interface Layer  
The users/UI layer enables users to interact directly with the DT to address their management and decision-making needs. Depending on their specific requirements, users can execute various analyses and simulations through functions such as data input, querying, visualization, control, and monitoring. The full range of capabilities provided by the data analytics/application layer, including road asset management, maintenance strategy, transportation management, simulation, evaluation, visualization, monitoring, and control (Figure 9), can be accessed through user-friendly interfaces supported by advanced tools. These interfaces may be provided via online web portals, desktop applications, mobile applications or platforms, APIs, or immersive environments such as VR/AR/MR or extended reality (XR), which integrates all these technologies. Additionally, automated dashboards featuring GIS-based visualization can deliver results in various formats, including interactive maps, schematic diagrams, tables, charts, and other visualization methods, enabling users to gain insights from the DT system [35, 37]. Cross-platform game engines, such as Unreal Engine and Unity, can also be used to visualize 3D models and facilitate information interoperability [32, 40]. Comparison Between the Proposed DT Framework and the ISO 23247-2 DT Reference Model for Manufacturing  
This section compares the proposed DT framework with the ISO 23247-2 DT reference framework for manufacturing to facilitate a clearer understanding of the proposed model and encourage its adoption by researchers and practitioners (Figure 10). As previously mentioned, the manufacturing reference model comprises four domains: the OMD (e.g., assets), device communication (data collection and device control), DT, and users. The first domain, OMD, lies outside the DT framework and provides the DT with information regarding physical assets, such as personnel, equipment, materials, processes, products, facilities, and the environment. The OMD is monitored and controlled through the device communication domain. Figure 10: Comparison between the proposed model and the ISO 23247-2 DT framework. In the proposed model, the data acquisition and transmission layer performs a role similar to that of the OMD and the data collection sub-domain in the manufacturing framework. This layer provides the DT with context-specific data from physical assets--such as roads, bridges, or tunnels--whether they are in as-built or as-planned conditions (Figures 6 and 7). Furthermore, similar to the OMD, contextual data may be derived from sources such as workers, machines, materials, and smart work environments, as demonstrated in smart construction applications [52]. The acquired data are then transmitted to the data processing, integration, and storage layer for further processing. In the manufacturing framework, the device communication domain obtains data from physical assets through its data collection functionality and performs the control and actuation of devices within the OME. Therefore, this domain achieves synchronization between the OMEs and their corresponding DTs. Conversely, in the proposed model, asset or device control is executed through the data analytics/application layer. The data processing, integration, and storage layer receives asset data from the data acquisition layer and processes the raw data for further refinement, categorization, and modeling within the data modeling layer. It functions as an intermediary linking road assets to their DT counterparts. Given its primary functions, this layer corresponds closely to the data pre-processing functional entity (FE) within the data collection sub-domain of the manufacturing framework, where activities such as data filtering and aggregation occur. The DT domain is the core of the manufacturing framework and governs the overall operation of the DT.