This paper examines the performance of different active control strategies for improving lateral stability of car-trailer systems using numerical simulations. For car-trailer systems, three typical unstable motion modes, including trailer swing, jack-knifing and roll-over, have been identified. These unstable motion modes represent potentially hazardous situations. The effects of passive mechanical vehicle parameters on the stability of car-trailer systems have been well addressed. For a given car-trailer system, some of these passive parameters, e.g., the center of gravity of the trailer, are greatly varied under different operating conditions. Thus, lateral stability cannot be guaranteed by selecting a specific passive parameter set. To address this problem, various active control techniques have been proposed to improve handling and stability of car-trailer systems. Feasible control methods involve active trailer steering control (ATSC) and active trailer braking (ATB). Recently, a variable geometry approach (VGA) has been investigated. The essence of this method is to actively control the lateral displacement of the car-trailer hitch in order to improve high-speed stability of the vehicle system. To derive the three controllers, their respective yaw plane models are introduced. The simulation results based on each control method are examined and compared against each other. Through the benchmark comparisons, the features of different control strategies are identified and their applicability discussed.