Road safety barrier

1. A retainer for use in a wire rope road safety barrier, the wire rope safety barrier comprising a plurality of posts for supporting one or more wire ropes above the ground, the retainer comprising:

an arm for embracing at least half of a circumference of the post whereby the retainer can be held on the post at a position along its length, and

a tab extending from the arm for retaining the wire rope against the post, the tab being frangible or yieldable at a break point when subjected to a lateral force by the wire that exceeds a predetermined amount of force to permit a separation of the wire rope from the road safety barrier within a predetermined impact zone,

wherein the post includes an outer surface,

wherein the arm includes an upper edge, a lower edge and an annular surface configured to engage with the outer surface about at least half of the circumference of the post when the retainer is held on the post, the annular surface having a first width defined as a vertical distance between the upper edge and the lower edge when the retainer is held on the post, and

wherein the tab is attached to the arm at the break point and includes an arcuate portion configured to engage the wire rope and a region attached to the arcuate portion, the region providing a planar surface configured to engage the outer surface, the planar surface having a second width being defined by a horizontal distance between a first edge and a second edge of the tab when the retainer is held on the post, and

wherein the first width is less than the second width.

2. The retainer according to claim 1 , wherein the arm is in the form of a ring.

3. The retainer according to claim 1 , wherein the arm is in the form of a split ring that can be positioned on the post from a direction transverse to a longitudinal axis of the post.

4. The retainer according to claim 1 , wherein said predetermined amount of force is inversely proportional to a lateral extent along a line of the road safety barrier of an impact zone that is subject to a wire rope deflection.

5. The retainer according to claim 1 , wherein the tab is configured to press the wire rope against the post.

6. The retainer of claim 1 , wherein the region includes a first end, and

wherein the arcuate portion of the tab includes a first end attached to the break point and a second end attached to the first end of the region.

7. The retainer of claim 1 , wherein the arm is in the form of a split ring including a first free-end and a second free-end separated by a gap,

wherein the arm allows the gap to be temporarily expanded to allow the arm to be secured to the post by engaging the arm with the post in an axial direction relative to a longitudinal axis of the post.