A welded tubular structure inside a vehicle that protects occupants in case of a rollover or impact. Required for many forms of motorsport.
Roll cage is a welded tubular steel structure installed inside a vehicle to protect occupants in case of a rollover or impact. The cage typically consists of a main hoop behind the driver, a front hoop ahead of the driver, side bars, harness mounting points, and various connecting tubes that triangulate the structure for rigidity and impact resistance.
Roll cage design and construction is regulated by motorsport sanctioning bodies (FIA, NASCAR, NHRA, etc.) for cars used in racing. The specifications cover tube material (DOM steel, chromoly), tube diameter (typically 1.5 to 1.75 inches), wall thickness, and configuration (number and placement of tubes). The construction must be welded by certified welders to specifications appropriate for the racing class.
Roll cages are required in most forms of organized racing (drag racing above certain speeds, all road racing, all rally, all drift competitions in major series). They are not required for amateur track days in most cases. Roll cages compromise daily driving practicality (added weight, reduced interior space, reduced rear visibility) and are generally not installed on cars used as daily drivers.