# Usage of V2X Applications in Road Tunnels
## 6 Future Work  
Positioning improvements are needed and should be considered in future V2X communication strategies, as well as urban planning and city management, because the availability of GNSS positioning is limited. However, for many applications, the GNSS approach is only one working solution. In some cases, an assisted approach could be used, e.g., for navigation, route planning, etc. However, in V2X communication, the centralized positioning approach is required at the level of the entire tunnel. The centralized approach is needed for the synchronization of all units placed in the tunnel at that moment.  
A progressive approach is the use of BLE-based communication [46] as a complement to C-ITS, which can very accurately detect indoor positions [47], for example, vehicles in the tunnel, by transmitting accurate information to the navigation and tunnel control system with the minimization of cost investments. The application is planned for future work and further development, and its usage for the V2X application will be considered in the subsequent experimental studies.  
Positioning for the purposes of V2X communication in the tunnel could be based on the specific approach of the roadside unit (RSU) positioning [16; 17], which could be implemented in the tunnel, and not only in positioning, but also in transmission of V2X data and its dissemination throughout the tunnel. Further applications could also be applied, and the RSUs could be connected to the tunnel control system and devices in the tunnels, such as variable message signs, etc. This approach could be a systematic way of how to use assisted localization methods with limited GNSS availability. The main advantage is the possibility of implementing further functionalities, such as time corrections. Furthermore, the security aspects of advanced approaches should be prepared, especially for the operation of autonomous vehicles, where security is crucial [48; 49; 50].  
It is also necessary to perform advanced analysis on more data, in all parts of the tunnel, but also in different tunnels to ensure that the solution could be applied everywhere. It is absolutely essential to prove the same with other V2X units.  
Methodology, J.B. and T.T.; testing, J.B. and T.T.; formal analysis, J.B.; data curation, J.B.; writing--original draft preparation, J.B.; writing--review and editing, J.B., T.T., V.A., and Z.B.; visualization, J.B.; supervision, T.T. and V.A.; project administration, T.T. and Z.B.; funding acquisition, T.T and Z.B. All authors have read and agreed to the published version of the manuscript. This research was funded by the Technology Agency of the Czech Republic (grant number CK01000163), and by the Department of Transport Telematics CTU in Prague, Faculty of Transportation Sciences.  
Not applicable.  
Informed Consent Statement: Informed consent was obtained from all subjects involved in the study.  
Data Availability Statement: Data are available from the authors after an official request.  
The research was supported by the Technology Agency of the Czech Republic under the research project \"Research of alternative methods of position determination and its integrity with GNSS for drivers using C-ITS\" No. CK01000163, and also this article was supported by the Grant Agency of the Czech Technical University in Prague, grant No. SGS22/121/OHK2/2T/16, \"Usage of BLE devices for determining the position and speed of the vehicle in the tunnel\" as well.  
The authors declare no conflict of interest.