Gating terminals allow controlled penetration along a portion of its length.  For example, Energy Absorption Systems manufactures a gating system called Universal Barrels (a.k.a. Fitch Barrels).

Non-Gating terminals provide full redirection capabilities along its entire length.  Connecticut DOT provides free plans for a non-proprietary non-gating system called the Narrow Connecticut Impact Attenuation System (NCIAS).

Unique Redirective-Gating Attenuator

Firstly. when a vehicle impacts near the back of the CIAS, it "redirects" the vehicle away from the fixed object, so this is its redirective capability.

Secondly, the CIAS "captures" vehicles impacting at or near the nose and along its sides.  This is the gating capability of the CIAS.