Currently, numerous single track railway lines are disused due to economic reasons. One way they could be reactivated for bidirectional on demand traffic is by small cabin-like vehicles, lateral stabilized by a system of control moment gyroscopes and a moveable mass. Regarding such a vehicle, there is currently no reference in comparison with other vehicles and no experimental experience or the like. To ensure the functionality and safety of the vehicle even before its realization, a model-based design is carried out for development, analysis, optimization and testing. This paper is focused on the co-simulation of such a vehicle that is controlled by a longitudinal control. In order to take into account the complex interaction between the longitudinal dynamics and the running gear, the entire system must be considered here including the wheel/rail interaction. Co-simulations are performed considering both the mechanical model of the vehicle and the control of the longitudinal dynamics of the overall system. The simulation results show that functionality and safe operation can be ensured by the vehicle longitudinal controls. As a result, the simulation and the measurement of the real system show a good match. By means of HIL and co-simulations, function tests could be shifted to earlier development stages, in order to accelerate the overall development.