Roll cage

As the name suggests a roll cage is integrated into the structure of the passenger cabin to protect the occupants in the even of the car rolling over onto its side or roof. A series of metal alloy bars are wielded in the shape of the passenger cabin of a car to form a roll cage. But the criteria for designing a roll cage for a car are not just associated with the shape of the passenger cabin of the car. A roll cage is designed to increase the rigidity of the cabin by having bars in significant energy absorption points of a cabin. 

All race cars are fit with roll cages to absorb the energy of an impact anywhere around the passenger cabin to protect the driver and co-driver. Like many other safety features on race cars roll cages have also made it to production cars to protect passengers. Many modern cars come with roll cages. The Hyundai Accent in India was one of the first affordable cars that came with a roll cage integrated into the structure of the car. 

Many convertible cars like the Volvo C70 and Mercedes Benz SL500 come with deployable roll hoops that are normally hidden in the body of the car. When the sensors detect that the car is about to roll over they deploy the convertible top along with the roll hoops that extend and lock in place and prevent the passengers from coming in contact with anything outside the passenger cabin. Modern convertibles also have a strong windscreen frame to act as a roll bar. Open top SUVs come with a roll bar on top just behind the driver to provide moderate roll over protection as the car has no roof. 

There are many different types of roll cages that vary for different applications in different race series and different cars. Roll cages are also used to stiffen the chassis on a race car to improve handling and reduce body roll. This is done by running bars across the back of the passenger cabin.

Prodrive a company that is a leader in technology and safety systems for rally cars has recently developed a new type of roll cage for the Mini John Cooper Works WRC. The new roll cage has curve shaped door beams to withstand much higher impacts. Side impact protection and roll over impact is significantly improved. The new roll cage will make its way into normal road cars to improve safety.