These guardrail end terminals were developed for the sole purpose of saving lives.
The first generation terminals that was tested and then subsequently approved by the Federal Highway Administration (the large square head) worked very well.
The second generation was introduced in the late 90's and worked perfectly.
The third generation was introduced in 2000-2001, it begins to work until the head encounters the first guardrail splice and then begins to choke..
The current (fourth) generation which was introduced in or around 2004. This version has a 4" feed channel and is the most common End Terminal to date, frequently chokes.