The producer surplus(PS) is defined as fare revenues minus operations costs for the operator. Operations costs increase with the number of trains, the number of passengers, travel distance and travel time. We use a cost function used in Swedish appraisal, where operations costs are assumed to be linear in train operating time (niti), passenger time(Diti) and passenger distance(DiL). The producer surplus of a change of travel times and the number of trains from situation 0to situation 1 is then