Rollover of heavy vehicle is an important road safety problem worldwide. Although rollovers are relatively rare events, they are usually deadly accidents when they occur. In order to improve roll stability, most of modern heavy vehicles are equipped with passive anti-roll bars to reduce roll motion during cornering or riding on uneven roads. This paper proposes an H ∞ approach to design active anti-roll bars using the yaw-roll model of a single unit heavy vehicle. The control signals are the torques generated by the actuators at the front and rear axles. Simulation results in both frequency and time domains are provided to compare two different cases: passive anti-roll bars and H ∞ active anti-roll bars. It is shown that the use of two H ∞ active (front and rear) anti-roll bars drastically improves the roll stability of the single unit heavy vehicle to prevent rollover.