Which suspension component primarily controls the lateral stability of a vehicle?

The component that primarily controls the lateral stability of a vehicle is the sway bar. The sway bar, also known as an anti-roll bar or stabilizer bar, is designed to reduce body roll during cornering by connecting the left and right sides of the suspension. When a vehicle turns, the body tends to lean to one side due to centrifugal force. The sway bar helps balance this force by creating a resistive force that limits the amount of lean, thus enhancing lateral stability and improving handling.

In contrast, control arms, leaf springs, and torsion bars primarily serve different functions. Control arms are essential for connecting the wheel assembly to the vehicle's chassis and allowing for vertical movement, but they do not directly address lateral stability. Leaf springs and torsion bars are more focused on supporting the weight of the vehicle and managing vertical loads, rather than improving stability during lateral movements. Hence, the sway bar is specifically engineered to enhance lateral stability, making it the correct answer to the question.