The directional and handling responses of articulated heavy vehicles are known to be somewhat less predictable, particularly under emergency-type maneuvers. This poses complex control challenges for the driver and the road safety. Moreover, the yaw stability of an articulated vehicle is very sensitive to vehicle forward velocity and cargo load, which could vary considerably. The vast majority of the active safety control strategies in the literature, however, focus on assessments of stability limits and controller considering constant forward speed. In this paper, a gain-scheduling optimal control technique is proposed for enhancing yaw stability limits of articulated commercial vehicles considering a broad range of forward speeds. For this purpose, an optimal feedback control method is used to design a family of yaw moment controllers corresponding to different vehicle velocities. Each yaw moment controller is designed such that the instantaneous tractor yaw rate and articulation angle responses track the target values at each specific speed. A gain scheduling mechanism is subsequently constructed via interpolations among the controllers corresponding to each constant forward speed. The proposed method permits on-line updating of the control gains with variations in the vehicle speed, and thereby proved greater robustness and improved control performance under varying speeds. The effectiveness of the proposed yaw stability control scheme is evaluated through software-in-the-loop (SIL) co-simulations involving Matlab/Simulink and TruckSim under path-change maneuvers at various forward speeds. The relative merits of the proposed gain-scheduling optimal control are illustrated by comparing its performance with that of the conventional optimal feedback control method. Simulation results demonstrate that the proposed gain scheduling optimal control can yield enhanced yaw stability limits of articulated heavy vehicles at different vehicle velocities, by making the tractor yaw rate and articulation angle follow the desired values over a wide range of forward speeds.