Today at the auction they had safety release straps . Two kinds. The regular nylon and one with an elastic tie wrap in between. There was a lunge rope with the same. Do you know why? Are they for horses you have difficulty tieing? We need a pair but it just seemed to me that it was one more weak link that could be broken.
Everything that we tied with has safety release snaps, we use lines that are slightly elastic in the trailers - they give a little. Is that what you mean? I don't know why they would put that in a lunge line but there must be a logical reason I guess.
There's some value in the elastic trailer ties, in that they resist, but it isn't a hard cold solid restraint that sometimes is the trigger for panic, the harder they pull, the more resistance, but they can learn to stop at a lighter touch too. we used to have a section of bicycle inner tube on tie lines at a stable I was at.
Quick releases are really good to have at the fasten point in the trailer, in case of emergency where you either can't get the knot undone, or they are pulling against it too much to undo regular snaps. Especially if there has been an accident.