On an open go-kart chassis, what safety structure is absent?

On an open go-kart chassis, the absent safety structure is a roll cage.

An open kart has no roll cage surrounding the driver. Its protection instead comes from the low seating position, the open-wheel layout, protective bodywork or bumpers, and the driver’s equipment. The design is standard in much sprint and circuit karting, where a cage would add weight and change the kart’s handling characteristics.

A caged kart is a different chassis type: a tubular structure surrounds the driver and is used especially in some dirt-track and oval-kart applications. The distinction is about the frame’s construction, not whether the kart is safe or whether it has a steering wheel. Open karts still need steering wheels, seats and braking systems to operate.

A seat belt is also not the defining missing part. Many racing karts do not use car-style seat belts because a restrained driver can be exposed to different risks in a lightweight, open vehicle. Safety rules instead emphasize helmets, gloves, suits, suitable footwear and track barriers, with exact requirements varying by class and governing body.