A roll cage is a specially constructed frame built in or around the cab of a vehicle to protect the occupants from being injured in an accident, particularly in the event of a roll-over. Roll cages extend in front of the driver, next to the A-pillar, to provide as much high-speed protection as possible in a coupé. This is compared to the protection provided in open wheel racing, where a solid shell encases the majority of the driver's body as well as a rollover hoop that extends over the driver's helmet. A roll cage can also do a great deal to stiffen the chassis, which is desirable in racing applications.

A roll bar is a single bar behind the driver that provides moderate roll-over protection. A targa top is a body style that integrates an externally-visible roll bar that a semi-convertible top attaches to. Convertibles have particular concerns for roll-over protection. In most modern convertibles a strong windscreen frame acts as a roll bar.

Roll hoops are essentially two roll bars, one behind the driver and one behind the passenger. Sometimes just a single roll hoop behind the driver is used. Sometimes they are integrated into the design of the body.

A newer form of rollover protect is deployable roll hoops that are normally hidden within the body of a car. When sensors detect an imminent rollover, the roll hoops quickly extend and lock in place. Cars that have a deployable rollover protection system include the Peugeot 307 CC [1], Mercedes-Benz SL 500, and Jaguar XK.

A sway bar (also stabilizer bar, anti-sway bar, roll bar, or anti-roll bar, ARB) is an automobile suspension device. It connects opposite (left/right) wheels together through short lever arms linked by a torsion spring. A sway bar increases the suspension's roll stiffness -- its resistance to roll in turns, independent of its spring rate in the vertical direction.

The first is the reduction of body lean. The reduction of body lean is dependent on the total roll stiffness of the vehicle. Increasing the total roll stiffness of a vehicle does not change the steady state total load (weight) transfer from the inside wheels to the outside wheels, it only reduces body lean. The total lateral load transfer is determined by the CG height and track width.

The other function of anti roll bars is to tune the high g / limit understeer behavior of the vehicle. The limit understeer behavior is tuned by changing the proportion of the total roll stiffness that comes from the front and rear axles. Increasing the proportion of roll stiffness at the front will increase the proportion of the total weight transfer that the front axle reacts and decrease the proportion that the rear axle reacts. This will cause the outer front wheel to run at a higher slip angle, and the outer rear wheel to run at a lower slip angle, which is an understeer effect. Increasing the proportion of roll stiffness at the rear axle will have the opposite effect and decrease understeer.