To help maximize utilization of its existing infrastructure, the railway industry requires train service optimization models with headway constraints for state-of-the-art distance-to-go signalling systems. To this end, this paper introduces an approach for assessing train path feasibility in ETCS Level 2, Moving Block, and Virtual Coupling, that could be used to construct alternative graphs for timetable optimization. The methodology is the first for distance-to-go signalling systems that accounts for the impact of train acceleration and braking on the braking curve, guaranteeing a feasible and optimal timetable. The alternative graph models are specifically adapted to the train and signalling systems used, with the models for Moving Block and Virtual Coupling being the first with continuous representation of open track. The methodology is used to assess the capacity of Virtual Coupling and Moving Block, respectively, on the South West Main Line in the United Kingdom. The results show that Virtual Coupling can increase railway capacity compared to plain Moving Block, but this may depend on network topology.