i just saw a crash into one 2 weeks ago on my way back from goldie. a little hatch back had put the front right bar into the steel rope fence.
the damage wasnt too bad,,, it was drivable. it look like the wire had SLOWED down her car while she was against it. btw, the fence was still standing.
so i think theyre a good thing. but on a head on impact i wouldn't like to be in the car. the fences look like they could easily decapitate u.
so on a head on=bad
on grazes and brushes=good