We consider the problem of scheduling a maximal amount of additional, low priority transport through a large multiperiod network, given that we may not interfere with an existing schedule for high priority transport. The problem is transformed into the Time-Expanded network(TENET) without traverse time using TENET Generator (TENETGEN). We describe two specialized heuristic algorithms that guarantee the optimal solutions and show the effectiveness of them by comparing quite favorably with Dinic.