To determine with certainty the capacity of a railway line or network a train timetabling problem should be solved. However due to the size and complexity of this timetabling problem, simpler approximations and simulations are more often used in practice. Absolute capacity on the other hand may be more simply obtained by ignoring the possibility of collision conflicts which are manifested as interference delays and occur as a result of insufficient passing facilities. This is achieved by allowing trains to pass through one another on non-critical sections in the timetable. Under this assumption, the full timetabling problem may be considerably reduced. In this paper details of a timetabling approach are presented and the calculation of important parameters required in the approach. Mathematical models for solving both the full and reduced timetabling problem are then developed. Alternative heuristics however are also proposed and extended because the reduced problem is still of considerable size and complexity
