A roll cage is a specially engineered and constructed frame built in (or sometimes around, known as an exo cage) the passenger compartment of a vehicle to protect its occupants from being injured in an accident, particularly in the event of a roll-over.
There are many different roll cage designs depending on the application, hence different racing organizations have differing specifications and regulations. They also help 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. Due to the lack of a protective top, some modern convertibles utilize a strong windscreen frame acting as a roll bar. Also, a roll hoop may be placed behind both headrests (usually one on older cars), which is essentially a roll bar spanning the width of a passenger's shoulders.
A newer form of rollover protection, pioneered on the Mercedes-Benz R129 in 1989, 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, Volvo C70, Mercedes-Benz SL 500, and Jaguar XK.
Roll bars are also used historically on row crop tractors, and roll cages are common as part of the cab on modern tractors.
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A racecar roll cage sans body
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Roll bar on an Esther.
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Roll cage in a Porsche 997 GT3 RS.
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Roll hoops on an Audi TT.
Famous quotes containing the words roll and/or cage:
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—H.L. (Henry Lewis)
“Out of the cage came Eve,
escaping, escaping.
She was clothed in her skin like the sun
and her ankles were not for sale.”
—Anne Sexton (1928–1974)