## 1 Introduction  
The quality of the railway infrastructure is fundamentally important for infrastructure companies as well as the customers and passengers. Infrastructure companies are responsible for keeping their infrastructure assets in good, reliable, and serviceable condition. For this purpose, German infrastructure companies receive funding for the replacement of infrastructure from the German federal government. This funding is regulated in a contract between the government and infrastructure companies, the so-called Leistungs- und Finanzierungsveriepharung (LuFV) [1]. In addition to replacement, infrastructure companies also perform maintenance to preserve and improve the condition of assets. Most railway infrastructure companies receive financial support from public funds. Expenditure per person is particularly high in Luxembourg [2] and Switzerland [3], for example. In Switzerland, the financing and expansion of the railway infrastructure are provided by the Railway Infrastructure Fund and the Strategic Railway Infrastructure Development Program. The federal government uses the funds to finance the railway infrastructure costs. This includes the operation, maintenance, and expansion of the railway infrastructure [4]. The infrastructure assets of the railway stations are also part of the railway infrastructure in Switzerland according to Article 62, Paragraph 1 of the Railway regulations in Switzerland [5]. To be able to measure the quality of the infrastructural assets, quality indicators in Germany are defined in the LuFV. Quality indicators are used to ensure reasonable financial input and good infrastructure conditions. Different quality indicators are used for various railway infrastructure assets. For track infrastructure, several indicators are used to describe the condition of the infrastructure [6]. In [7], the quality indicators for the assessment of station infrastructure are described. However, since the correlation between financial funding and infrastructure quality was previously unknown, railway infrastructure companies were asked to scientifically establish a cause-effect relationship in the newly adopted LuFV III [7]. This cause-effect relationship should be bidirectional and transparent in order to determine future target values and budgets for respective quality indicators. A bidirectional relationship means that both the infrastructure quality expected, using a fixed financial budget for replacement and maintenance measures, and the budget required for a specified target quality can be calculated. To determine the expected quality for a certain budget, the overall financial budget must be given as input. More specifically, the total budget must be distributed among the different infrastructure assets. Various scenarios can be generated for budget allocation to infrastructure assets. In addition to budget allocation, the prioritization of the measures required is also an elementary part of the cause-effect relationship. The cause-effect relationship can be used to analyze different strategies for budget allocation and the prioritization of measures. To establish a cause-effect relationship between financial budget and infrastructure quality, both degradation functions and the effects of maintenance and replacement measures must be defined. In this paper, the cause-effect-relationship for the railway station infrastructure assets of DB Station&Service AG--the German infrastructure operator for railway stations--is discussed. Station infrastructure includes assets and facilities at passenger stations. Track facilities that serve railway operations are not part of the station infrastructure and will not be considered. This paper aims to describe different budget allocation and prioritization strategies and to analyze their effect on measured quality indicators. An elementary component of the development of a cause-effect relationship as described, alongside replacement and maintenance with their effects and costs, is the degradation of investigated infrastructure.