Deceleration distance is the vertical distance a falling worker travels between activation of a fall arrest device (such as an energy absorber or self-retracting lifeline) and the moment they come to a complete stop.
Why it matters
This value is critical when calculating total fall clearance below the work surface — getting it wrong can result in the worker striking the ground despite the fall arrest system functioning correctly.
Standard limits
ANSI Z359 limits shock-absorbing lanyards to a maximum deceleration distance of 1.07 m (3.5 ft).
Total fall clearance formula
Clearance required = lanyard length + deceleration distance + worker height (D-ring to feet, ~1.8 m) + safety margin (typically 1 m).