Freight railways are the major means of transportation of bulk material, such as iron ore from the origin to the destination. Usually for heavy haul railways, the detination is a port. To improve profit and ensure the quality of services of a railway, a good timetable design is crucial. However, all the work provided on the Train Timetable Problem, an NP-hard problem, is usually only applied locally to a single railway. This article deals with the train timetabling problem applied to mixed traffic railways with both cargo trains and passenger trains sharing the same resources with different priorities. Moreover, a public base benchmark of problems is proposed so that future work can be compared. This base is used to show that the problem cannot be solved to optimality within a reasonable time frame for production sized instances, and a genetic algorithm is proposed.