Chris - good link, thx.

Mike - I think the main reason not to use a rope is strength. The loads produced by a 150-200 lb human fetching up against a lifeline are enormous. Besides the kinetic energy of the body, the fact that the line will take the load at 90 degrees or so from its strongest dimension (linear) would require that the line be sized pretty large for any kind of safety factor. Maybe one of those fancy new synthetics that are as strong as steel would work. But I don't think you could get a line strong enough to fit through the holes in a stanchion, it would be too large.

I've got some 1/4" 3-strand woven through my stanchions right now, Totally inadequate for the job as a lifeline for a human, they do work for a CrewDog. I forget when it was that I put them on, sometime in the summer, when I mounted the stanchions. The line grows mildew fast there, faster than you would think, it being as exposed as it is. It also tends to be stretchy; easily adjusted, but not very "secure" feeling when you grab it.

Just some thoughts...