# Deep Neural Networks for Spatial-Temporal Cyber-Physical Systems: A Survey
## 3 DNNs in CPS-Based Spatial-Temporal Data
### CPS Application Domains
#### 3.2.1 Transportation CPS  
It is popularly known as smart transportation. Physical systems are integrated with computational and communication techniques to realize various goals, such as improving traffic flow, toll collection, reducing congestion, smart parking, enhancing safety, safe pedestrian crossing, reducing carbon emissions, and autonomous driving, among others. Transportation CPS is a sophisticated, heterogeneous system that intends to offer effective services connected to various modes of transportation and traffic management. Transportation CPS manages a variety of new data sources, including geospatial transportation area, connected vehicle, roadside unit (RSU), and traffic network data. It also empowers users to be better informed and use transportation systems in a more innovative, safer, and organized fashion. Smart transportation technology can offer services such as utilizing cameras to enforce traffic regulations, dialing 911 in the event of a car accident, and tracking the speed limit of vehicles, among others. There are several forms of security and privacy issues related to transportation CPS, targeting its essential elements such as IoT devices (sensors, actuators, microcontrollers, etc. ), cloud services, and location-based services, among others. Examples of security issues include data tampering, man-in-the-middle (MITM) attacks, eavesdropping, impersonation, distributed denial of service (DDoS) attack, and artificial intelligence (AI)-based attacks, etc. In addition, model inversion, model poisoning, model evasion, and model extraction are typical ways of attacking AI models, which leads to severe impacts on driverless cars. While location privacy and commuter privacy are among the privacy concerns. To address the security and privacy issues in transportation CPS, both industry experts and researchers in academia are actively engaged in research to solve the problems. Nonetheless, despite these challenges, transportation CPS has the potential to revolutionize transportation systems, making them safer, more efficient, and more sustainable. Transportation CPS can be categorized into vehicle transportation (which involves the integration of computing, communication, and physical systems within a vehicle); infrastructure transportation CPS (which consists of the integration of computing, communication, and physical procedures in transportation infrastructure); and system-level transportation CPS (which involves the integration of computing, communication, and physical systems at the system level). Vehicle transportation CPS includes sensors, actuators, embedded systems, autonomous driving, etc. The main goal of vehicle transportation CPS is to improve safety, energy efficiency, and user experience. Transportation infrastructure for the transportation CPS includes traffic lights, sensors, cameras, communication networks, and other components that enable traffic monitoring, control, and management. The main objectives of transportation infrastructure CPS are to increase safety, improve traffic flow, and lessen congestion. System-level transportation CPS includes data analytics, simulation, optimization, and control algorithms that enable efficient and effective transportation planning, operation, and management. The main goal of system-level CPS is to improve the overall performance and sustainability of transportation systems. Real-time requirements for processing large amounts of data, secure communication mediums, interoperability among different systems, and effective collaboration between different stakeholders are among the challengesfaced by transportation CPS nowadays. However, despite these challenges, transportation CPS has the potential to revolutionize transportation systems, making them safer, more efficient, and more sustainable. As shown in Figure 4, using the autonomous car as an example in the transportation CPS domain, the sensors/actuators will collect and send spatial-temporal data of the moving vehicle.