The decentralised railway signalling systems have a potential to
increase capacity, availability and reduce maintenance costs of
railway networks. However, given the safety-critical nature of
railway signalling and the complexity of novel distributed
signalling solutions, their safety should be guaranteed by using
thorough system validation methods. To achieve such a high-level of
safety assurance of these complex signalling systems, scenario-based
testing methods are far from being sufficient despite that they are
still widely used in the industry. Formal verification is an
alternative approach which provides a rigorous approach to verifying
complex systems and has been successfully used in the railway
domain. Despite the successes, little work has been done in applying
formal methods for distributed railway systems. In our research we
are working towards a multifaceted formal development methodology of
complex railway signalling systems. The methodology is based on the
Event-B modelling language which provides an expressive modelling
language, a stepwise development and a proof-based model
verification. In this paper, we present the application of the
methodology for the development and verification of a distributed
protocol for reservation of railway sections. The main challenge of
this work is developing a distributed protocol which ensures safety
and liveness of the distributed railway system when message delays
are allowed in the model.