A 3:1 (Z-rig) haul system is commonly used in rope access rescue primarily because:
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A
It provides a 3:1 mechanical advantage, tripling the hauling force relative to input force
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B
It allows the rope to be rigged without any additional equipment beyond standard ascenders
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C
It is the only haul system approved by SPRAT for rescue operations
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D
It automatically locks if the haulers release the rope