# Application of Digital Twin in Handling and Transportation of Hazardous Chemicals
## 3 Methodology
### Basic Functions of the DT System  
Considering the needs of different types of users from different perspectives, the system functions should meet the following aspects, and the specific details are shown in Figure 3.  
Figure 3: Basic functions of the system. Figure 2: The framework of the constructive of DT system for hazardous chemicals. (1) Terminal and station patrol inspection. The purpose of the DT system is to effectively present the 3D appearance of the whole process of hazardous chemical loading, unloading and transportation. The high-precision, detailed and dynamic expression of the participants in each link enables managers to conduct aerial inspection of any link at any time and find security risks and technical loopholes from a broader perspective. (2) Risk discrimination. Use the visual interface to identify the risk points in the operation. According to the route of tankers in the station, judge whether the operation is reasonable, and whether the existing loading and unloading process is reasonable. Further, for the new pipelines in the station, observe the rationality of profile setting from all angles with the help of the system. (3) Simulation of rescue plan. Many scholars have conducted expensive research on hazardous chemical traffic accidents, and have an understanding of the evolution mechanism and propagation path of fire, explosion and other accidents [30; 31]. Once some changes happen in the real world, the corresponding reaction is presented in DT, so by setting the location and scale of various accidents in DT, the system simulates accident impacts on surrounding traffic networks and residents. The next step is retrieving the rescue plan or traffic control strategy from the accident rescue resource pool, applying these specific operations regarding rescue, and verifying the effectiveness of rescue plans relying on the system simulation platform. By evaluating the simulation results, experts can moderate and improve accident disposal schemes. (4) Transportation tracking. The main purpose of the system is to understand the current driving state of each tanker loaded with hazardous chemicals, and display the position, speed, loading capacity and other information of the vehicles in the system. Every vehicle must install GPS and other sensors to provide location according to Chinese law, chemical companies and terminals usually have their own monitoring system, companies will ask drivers to feedback their information. We need is to collect this data and integrate it into DT. (5) Driving behavior simulation. Invite drivers to participate in simulated driving in different scenarios at the initial stage of system establishment, collect drivers' reactions in sections with complex traffic conditions, mixed traffic and lane changing of different types of vehicles, and collect vehicle acceleration, turning speed, the turning radius of key sections, and other information into the vehicle driving simulation module of the system, to enhance the effectiveness of the driving behavior simulation. (6) Accident prediction. Many sensors have been set in the cab to monitor the driver's unsafe behavior [32; 33]. The DT system combines algorithms for special usage, such as lane-changing behavior [34], this kind of algorithm is integrated into the system, and the environmental parameters detected by the vehicle are substituted into the calculation, when the tanker drives onto an accident-prone road section, it monitors the road conditions and traffic flow status, predicts the lane-changing behavior of other vehicles, and reminds the driver through sensors, screens, and mobile phones. At the same time, the inspection results of the facilities in the station and the daily inspection results of tankers are entered into the system to automatically assess the risk. (7) Market information presentation. Enterprises pay attention to market revenue, and the state pays attention to mastering information such as economic and social development and industrial structure.