The intended audience for this paper is not primarily railway planners but people working with appraisal methodology .Appraisal methodology covers all sorts of inputs, valuations and processes, from future fuel prices to the value of a statistical life. To ensure that CBAs for different investments can be compared and ranked consistently, there are often national guidelines for appraisal methods, inputs and parameters. In contrast, principles for timetable construction are surprisingly neglected. The ultimate objective of this paper is to start a discussion about such principles. Again, which timetable principle is appropriate depends on the prevailing institutional setting the incentives of the involved stakeholders and the process for resolving capacity conflicts. The principle needs to capture the essential interactions between demand, supply, capacity constraints and the capacity allocation process. Once such a principle is established, it can be used to calculate timetables both in the do nothing and in the investment scenario..