A Hardware-in-the-Loop (HiL) system for Electronic Control Units (ECU) of electro-pneumatic brake systems is presented. The HiL system runs a real-time capable vehicle model comprising of both the vehicle dynamics and the electro-pneumatic brake system.The dynamic behaviour of the vehicle can be simulated either by a real-time multi-body vehicle model or by a simpler system dynamic (double-track) model. To assess the quality of the system dynamic vehicle model, it is compared to a multi-body vehicle model which was validated with comprehensive experimental results. Discrepancies can be seen for highly unsteady manoeuvres. Reasons for these discrepancies caused by the modelling topology of the system dynamic vehicle model are given.In order to simulate the electro-pneumatic brake system, a real-time model has been developed and validated. The different topologies of brake systems can be assembled from components and integrated into the vehicle model. The model of the brake system determines the transient response of brake torques at the wheels as a result of the electrical signals given by the ECU.The HiL system allows the simulation of anti-lock braking manoeuvres as well as manoeuvres that feature interventions of the Electronic Stability Control system (ESC). Using this developed approach, it is possible to estimate the consumption of air during an anti-lock braking manoeuvre or to assess the performance of the ESC during various manoeuvres. In the future, the presented system can support the homologation process of ESC by adjusting the parameters of the system in advance or by a virtual homologation of some of the numerous vehicle variants.