AS 1428.1 is the Australian standard for general design requirements for access and mobility. It governs how spaces, doors, and gates are designed so people with disabilities can use them. For gate work, the rule that bites most often is the clear-opening width.
The minimum clear opening for a single-leaf gate or door on a compliant access path is 850 mm. 'Clear opening' is the width with the gate fully open, measured between the leading edge of the leaf and the opposite door stop.
For a pedestrian gate, that means the gate leaf has to be at least 950 mm wide if the frame stiles eat 50 mm each side. For practical safety margin against build tolerance, spec a 1000 mm gate.
AS 1428.1 also governs handle types (lever handles, not knobs), latch heights (operable from a wheelchair), and threshold gradients. Pool gates are a separate standard (AS1926.1) which can override.