The harness was designed at Big MT's Y-17 medical facility with autonomous casualty recovery in mind. The suit tracks the vital functions of the user and, once a certain injury threshold is reached, it takes over the motor functions of the user and walks them to the designated home base out of harms way. It is a miracle of research, employing intelligent fibers and artificial muscle, rather than the crude hydraulics that dominated military technology back in 2077.
However, due to the prototypical status of these suits, they suffer from several major issues. First, if a home base is not defined, the suits enter an unpredictable wander state. Second, while it is possible to calibrate the upper injury threshold for the override to kick in, the sensors cannot detect if the user is still alive. Third, the suits record all user movements and can effectively "learn" to replicate their shooting and fighting reflexes, but lack any IFF software. All of these issues combined have led to them breaking out of the Big MT's research facilities and wreaking havoc around the crater.
With no defined home base and no ability to detect the death of the users, the suits acted as mobile coffins: soldiers and researchers trapped inside had no ability to shut them down and were forced to suffer a slow, agonizing death. Even after two centuries, the suits, still carrying the bones of their original users, continue to function, scouring the Big MT of undesirables.
The Y-17 trauma harnesses resemble nothing else than the walking dead, skeletons clad in red rubber suits, heads encased in spherical glass helmets. The suits have oxygen tanks on its back, which are in turn attached to additional armor plating around the neck and shoulder area, the area which the helmet is hermetically sealed to.
The Y-17 trauma override harness is a pre-War autonomous suit created to evacuate wounded soldiers from the battlefield by taking over their motor functions. However, certain design mishaps coupled with the harness recording feature resulted in these harnesses becoming literal walking dead, technological horrors stalking the Big MT.
The harness is coded in the game as a humanoid non-player character and it is wearing non-playable armor. Also, all harnesses are coded as female, and are affected by the bonus damage from the Lady Killer and Cherchez La Femme perks. Despite their semi-mechanical nature, they are not considered to be robots or power armor, and thus do not take EMP damage from weapons like the pulse gun or sonic emitter.
Although the suit contains a skeleton with no living tissue, limb dismemberment will display the same visual effects as dismembering any standard humanoid non-player character, including white flesh and red blood. It is also possible to eat the corpse if the Cannibal perk has been taken. Also, the harness may contain blood sausage or thin red paste upon death if players have the Them's Good Eatin' perk.
When decapitating one with a helmet, the helmet will break, but the skull won't come out. Oddly enough, gibs may include eyeballs.
If using the Living Anatomy perk it can be hard to tell its HP and DT, due to this non-player character's very long name which causes the HP and DT values to be pushed past the bottom edge of the screen.
The harness has a very similar appearance to the space suit, but without gloves. Sometimes, it even has a helmet.
Despite the lack of gloves, the suit is somehow able to manipulate the hands of its dead occupant and use them to operate weapons.
If the Courier stays close enough to a Y-17 trauma override harness, you can hear the occupant's bones rattling when it takes damage. This is even subtitled as "Small number of bones rattling.", and "Large number of bones rattling" upon its death.
Standing in the X-12 research center long enough could cause one harness to glitch up into the players area, transporting several others (all from the X-12 facility) with it. This can cause a dangerous firefight.
With the Wild Wasteland trait, the Y-17 master trauma harness will say "Hey, who turned out the lights?!" This is a reference to the Doctor Who episodes "Silence in the Library" and "Forest of the Dead" when a group of microorganisms called the "Vashta Nerada" ate a character (Proper Dave) during one of the episodes. Said character had been wearing an environmental suit that shares a passing resemblance to a space suit, and his skull had been pressed to the visor on his helmet while the Vashta Nerada inside the suit made it walk around, similarly to the helmet-wearing trauma harnesses. The suit also had a thought based communication system that tended to retain echoes of the user's consciousness known as "data ghosts" that deteriorated into repeating single sentences, "Hey, who turned out the lights" being the sentence repeated by the suit after Dave's death.