the invention relates to a decision procedure in combinational logic which requires a computing time of n for determining the congestion of a railway track system . the railway track system supports n trains , each with a route length of m itineraries . prior to setting a requested route segment for a given train , a query is performed to check train positions and whether the given train is allowed to travel on the track sectors to be used for the requested route segment , without causing a possibility that the track system may become congested . the processing steps can be reduced . a ) verification of whether a train can reach the next immediate track sector of a route ; b ) verification for a two - train variation whether a reference position of the first train prevents the second train from traveling on its route ; c ) new dependencies are created using transitivity and for combinations of two trains , a verification is made whether a cogent sequence exists . step c ) is iterated until no new dependencies occur or no train can reach its destination .