Hybrid or attenuator systems have an independent base plate and post linked together using a pin. This is a similar system as the hinged rockfall catchment systems. The angle between the post and base plate is variable and is controlled by retaining ropes attached to the head of the post which are anchored on the upslope side of the system.
Since there is no lower bearing rope it allows impacted material to pass through the plane made by the fence posts. The netting of the system extends down the slope below the base of the fence. This covers the lower slope, controlling the movement of debris as it progresses downward.
These systems are useful in limiting energy of projectiles and controlling movement of debris along long slopes. These systems work well in areas that experience a higher frequency of rockfall in which a traditional rockfall catchment fence system higher on the slope would be costly or logistically prohibitive to maintain.
There are no testing guidelines or certification processes for hybrid rockfall fences. With this said, 1:1 scale testing following the ETAG 27 guidelines has been carried out on certain Trumer systems up to 3000 kJ.