Computer simulations are utilised to study the energy used by heavy haul trains and the amount of energy that can be generated from dynamic braking of these trains; these studies allow the potential for the application of hybrid locomotives to be evaluated. An in-house written software package is used to perform simulations on the energy balance between energy usage and the energy generated from dynamic braking for heavy haul operations on two typical track routes in Australia. The simulation results show that the energy generated from dynamic braking can contribute up to 30% of the energy used in locomotive traction. Detailed analyses show that the locomotives can operate at an average power that is much less than full power, and an energy hybridisation potential factor is defined, with the maximum factor reaching a value of 63%. This factor indicates the considerable potential for using hybrid locomotive traction in heavy haul applications.