[AU N EGL]

Originally Posted by ScotsBrutesFan

An airfence is a a generic term used to mean one of two types of safety structure

1 an airbag which is inflated but has vents to allow the air out when someone/thing hits it. the deformation as the air is released absorbs the energy of the impact. Downside..it's possible to slide under this type of fence and hit the wall/barrier behind it unabated. This type is being replaced by ...

2 an air foam barrier, similar idea to 1 but instead of it being inflated, it's actually a large piece of foam which has lots of tiny air pockets. when on impact the air is squeezed out as the foam compresses absorbing the energy of the impact. These can be set further away from a hard barrier to allow them to mmove and absorb impact that way too. They can also be used instead of tyre walls at chicanes etc.

Number 2 sounds like the NASCAR "safe" walls.