Multibody simulations are widely used for the dynamic analysis of railway vehicles, including the acceptance of vehicle running behaviour. Among these, the freight vehicles have, generally, friction damped suspensions for which numerical modelling is particularly challenging due to the contacting geometries, the intermittent contact, and the frequent stick-slip transitions. The impact of modelling decisions of friction-damped suspensions on the acceptance quantities for vehicle behaviour is the focus of this work. The selection of friction models and tuning of their parameters is challenging. In particular, the selection of friction coefficients is not straight forward, as friction conditions vary during operation and over time. This work aims to address both problems. A model of a friction-damped freight locomotive is used to simulate the dynamic response of the vehicle under realistic operation conditions and assess the impact of the friction modelling decisions. The results show that the use of different friction models provides similar results if the parameters are appropriately tuned. In contrast, the selection of friction coefficients significantly impacts the acceptance quantities, with emphasis on the wheel-rail forces at small radius curve transitions. The results recommend that the standard should include variations of the friction coefficients used for the friction-damped suspensions.