OSHA requires fall protection with body harness and shock absorbing lanyards when working over certain heights.
The way the shock absorbing lanyards work is that basically they are woven so as to gradually reduce the shock by tearing themselves apart.
The problem with those lanyards is that they're basically ineffective with a fall of less than 15' because of the tearing action that slows you down and protects your spine.
This is all well and good, it's required in bucket trucks, too. In case something happens to the bucket that you're standing in. and as common bucket trucks have a 55' height, the 15' limit is pretty moot.
I wore mine for about four hours this morning rerunning wires in poles (we used Blue instead of brown, and I got called off the job before I could tell the helpers that they needed to brown tape the insulation).
Anyway, a bucket truck is a good place to use that safety lanyard.
Except it won't do a lot of good when you're in and out and forget to attatch the end to the top boom.