In this paper, firstly, we propose a modeling of a Railway Signalling System in Statechart and the system's dynamic behavior is analyzed in this model. This system is the ERTMS/ETCS (European Rail Traffic Management System/European Train Control System) Level 2 whose performance is evaluated in terms of the availability. Secondly, the epistemic uncertainties (imprecision) are introduced into the transition rates of the system and handled by a methodology based on two-phase Monte Carlo simulation. In the two-phase Monte Carlo simulation, epistemic variables are sampled in the outer loop and the model of the system is executed in the inner loop. The originality of this work lies in modeling the dynamic behavior of the ERTMS/ETCS Level 2 and proposing a methodology based on two-phase Monte Carlo simulation to evaluate the availability of the system considering epistemic parametric uncertainties.