A retractable horizontal lifeline assembly includes a lifeline, a drum, and a crank. The lifeline has an intermediate portion interconnecting a first end and a second end. The drum has a base and is rotatable. The first end of the lifeline is operatively connected to the drum and the intermediate portion of the lifeline is windable about and paid out from the base. The drum is operatively connected to a first anchorage structure. The second end is operatively connected to a second anchorage structure. The crank is configured and arranged to be releasably connectable to the drum and is rotatable to rotate the drum and tension the lifeline. The crank includes a tension indicator to provide indication when the tension in the lifeline has reached a predetermined level. The crank is capable of tensioning the lifeline to a level greater than the predetermined level.