Automatic sliding door with a drive unit and traversable door leaves (2, 3), which can be moved into an open position and into a closed position, wherein the drive unit has at least one electric drive motor with a transmission and an endless toothed belt, to which the individual door leaves (2, 3) are attached, by means of drivers on one face of the endless toothed belt, wherein the traversable door leaves (2, 3) can assume two different closed positions (4, 5), wherein the drive unit has a control unit, by means of which the door leaves (2, 3) can be traversed into the closed positions, or into the open position, wherein the door leaves (2, 3) can be traversed from the first closed position into the second closed position, characterised in that a first closed position is intended for normal driving operation, and the second closed position is intended for a safety requirement, wherein the door leaves (2, 3) are moved together into the first closed position such that a pin-form profile strip on a closing edge of one door leaf is moved only as far as into an opening region of a groove-shaped profile strip arranged on a closing edge of the other door leaf, so that the door leaves (2, 3) achieve a wind-tight and/or watertight closure in the first closed position, and wherein the door leaves (2, 3) can be traversed from the first closed position into the second closed position such that, in the second closed position, the door leaves (2, 3) adopt a form-fit connection with their closing edges (6, 7), which can be moved onto one another, wherein the pin-form profile strip of one closing edge penetrates into an entire overlapping region of the groove-shaped profile strip of the other closing edge. the drive unit has at least one electric drive motor with a transmission and an endless toothed belt, to which the individual door leaves (2, 3) are attached, by means of drivers on one face of the endless toothed belt, wherein the traversable door leaves (2, 3) can assume two different closed positions (4, 5), wherein the drive unit has a control unit, by means of which the door leaves (2, 3) can be traversed into the closed positions, or into the open position, wherein the door leaves (2, 3) can be traversed from the first closed position into the second closed position, characterised in that a first closed position is intended for normal driving operation, and the second closed position is intended for a safety requirement, wherein the door leaves (2, 3) are moved together into the first closed position such that a pin-form profile strip on a closing edge of one door leaf is moved only as far as into an opening region of a groove-shaped profile strip arranged on a closing edge of the other door leaf, so that the door leaves (2, 3) achieve a wind-tight and/or watertight closure in the first closed position, and wherein the door leaves (2, 3) can be traversed from the first closed position into the second closed position such that, in the second closed position, the door leaves (2, 3) adopt a form-fit connection with their closing edges (6, 7), which can be moved onto one another, wherein the pin-form profile strip of one closing edge penetrates into an entire overlapping region of the groove-shaped profile strip of the other closing edge.