A drive device is operable on the basis of a detection value of the somersault detection device. A closure device (16) closes the roof opening section (12) through the operation of the drive device. The drive device is a gas producer. The closure device is an air bag which is inflated by the gas producer but can also be a strap-shaped component. The drive device can also be a tractive wire unit. The closure device can also be a sun blind (16), in which an air bag is incorporated.
