# Determining the Optimal Positions of Infill Balise Groups for ERTMS/ETCS Level 1 Applications
## 5 Conclusions  
As is evident from the literature review, research and publications explicitly concerning ETCS level 1 and other current balise-based, spot transmission train protection systems are rare. Although there are several deployments of ETCS level 1 in operation, apparently no one has ever published a comprehensible, widely applicable method on how to effectively and optimally place the necessary infill balise groups. Some works were available concerning different aspects, but a complete workflow was not in their scope. Therefore, our work focused on designing and implementing the algorithm in Python and making it available to the community and the public. With our work, calculating the optimal positions of infill balise groups for ETCS level 1 applications is possible. The algorithm is designed to be accessible and simple to use while still allowing it to adapt to a broad range of scenarios thanks to the input parameters available to the user. With that, we have managed to create an algorithm that is not confined to a specific geographical, regulatory, or contextual area of use but applicable universally in the context of ETCS level 1. The chosen implementation using Python and JSON files for input and output features fast computation times and supports the application in different scenarios, as further automation could be added on top. The scientific value of our work lies in it being the possible foundation of future research on ETCS level 1 and its effects on operations and capacity. One could use the algorithm to optimally place infill balise groups when investigating the effect different ETCS configurations have on a larger scale, such as a line, a station, or a whole network, without the need for either default positions or manual placement. For that, we have made the source code available as open source [47]. During thorough testing and the first application of the software in the planning phase for a new ETCS deployment, valuable insights on the sensitivity to each of the parameters were gained and--if necessary--changes and improvements were implemented. Owing to the chosen boundaries and interfaces of the algorithm, all ETCS trains can be modelled in this framework, covering the theoretical, technically possible speed range of up to 500 km/h, as set by the Eurobalises used [14] to transmit the data to the train. The first applications most likely will be in much lower speed regimes of regional and secondary lines where the benefits of a system of lower complexity and high economic efficiency are much needed to accelerate the wide deployment and adoption of ETCS. Additional research might add the ability to calculate the braking curves and the derived deceleration values on its own without relying on the official Braking Curves Simulation Tool [44]. This would decrease the preprocessing phase and accelerate the process by a significant amount. The algorithm is focused on application in scenarios of ETCS; however, it could also be adapted for other technically related systems. The specifics of ETCS and its special braking curves and other influencing system parameters were considered. While working on this task, it became clear that additional future work is needed to fully map the application scenarios of this tool, especially considering the need to automatically optimize the locations based on more than one train type. To date, this task must be performed iteratively with the support of the software now available. Future research therefore might cover the development of suitable methods to optimize the positions of infill balise groups for more than one train type. For this to work, it is necessary to develop an appropriate KPI, e.g., an additional weighting for the additional runtime of each individual train, which takes multiple train types into account and serves as the optimization goal. For now, the optimization algorithm and software have reached a robust state, and the railway community shall be able to benefit from our work. Conceptualization, C.W. ; methodology, C.W. ; software, C.W.