# Urban Traffic Signal Control under Mixed Traffic Flows: Literature Review
## 3 Technological Background
### Intelligent Transportation System Overview  
The development of a sustainable transportation system requires efficient use of existing infrastructure and continuous integration of information and communication technologies. Data transmission, traffic flow control, and the administration of transportation networks are all made possible by the deployment and application of cutting-edge communications and electronic and computational capabilities. A large number of these systems were closed systems running independently or in a closed system environment. To deliver better and safer mobility and transition to ITS, these systems have to collaborate and interact with one another [13] as shown in Figure 1. The emphasis of this paper is on Advanced Traffic Management Systems.  
The key factor for the success of ITS is the technology to access, gather, and interpret measurement data collected by various traffic sensors and, among others, from CVs and CAVs related sensors. Generally, two types of sensing platforms can be distinguished in this case: intra-vehicular sensing platforms and urban sensing platforms [15]. As the name suggests, the intra-vehicular sensing platform gathers information about a vehicle's conditions, while urban sensing platforms gather data on traffic conditions. To capture data during V2V and V2I interactions, sensor technology is a crucial component. Based on the collected data, the transportation management system are then given access to these data for additional processing, analysis, and decision-making [15]. Thus, relying on CVs or CAVs eliminates classical problems with traffic data collection. Having the ability to communicate with the environment, CVs or CAVs can provide data beyond the line of sight of fixed-mounted classic sensors. Exploiting that detailed data from CVs or CAVs, the temporal and spatial characteristics of congestion can now be precisely determined. Thus, more effective traffic control and vehicle rerouting countermeasures can be planned and implemented. Computing with those new data sources can provide appropriate solutions, e.g., altering the timing of traffic signal programs, disseminating data via variable message signs and vehicle navigation systems, or even planning new road capacities. Moreover, collected data from CVs or CAVs can also be used for the evaluation of implemented congestion countermeasures [16].  
The implementation of ITS solutions based on CVs or CAVs has advantages for every entity in the traffic and transportation ecosystem. It is manifested in the improvement of the overall transport network level of service. The advantages for society include a decrease in traffic accidents by promoting safe driving. Furthermore, traffic congestion decrease can be achieved by proper and timely traffic information distribution, which will also benefit by reducing the environmental impact of traffic. Road maintenance services will benefit from exploring traffic data and detecting unsafe regions and frequently congested places. Furthermore, the drivers will gain benefits in terms of expenses, comfort, and safety.