The way the maintenance activities of the railway infrastructure in the Netherlands have been performed has changed over the past ten years, due to a changing relation between the companies working in the railway sector. This has lead to new contracting models for maintenance, where the responsibility for the performance of the activities has shifted from the railway company to the contractors. Care must be taken however to use this model of contracting for signalling systems. Due to the nature of these systems it is difficult to find the right performance specifications which give the contractors freedom in their activities, but still maintain a high level of safety. Therefore the signalling systems must be carefully analysed to be able to determine which maintenance can be contracted using performance specifications and which maintenance must be prescribed.