From Halo Bulletin 8-15-12: 

Pioneer Specialization: Spartan optimization for deployment into uncharted, hostile territory (such as uncolonized worlds or Forerunner constructs like Requiem) for the purpose of gathering/relaying information.

Fast Track Armor Mod: The Fast Track armor mod allows Spartans to gain more experiential data from each encounter, effectively ranking up quicker during the process.

The Fast Track armor mod features armor that has wiring which runs throughout the armor to control temperatures in extreme conditions. Gameplay-wise, it gives the player more post-game experience. In-game, if you get 10 points per kill, you don’t get more at that exact moment, but after the game it modifies the amount of experience your Spartan earns to increase the speed at which you rank up. It’s not for everybody because it takes up a primary spot (that could be used for something like carrying an extra grenade or sprinting longer). And, in case you were wondering, you can’t change to it at the end of a game and get more experience for the entire match. Yes, we’re on to you…

HFFL’s thoughts:

Objective: Plain and simple it’s an EXP booster. Though don’t try to switch to this mod at the end of a game to boost the whole game’s experience. 343 has that taken into account and built in a fail safe that will only allow for more experience while the mod is active.

Subjective: I actually like this one and can see it being used often for those of us who want to get a lot of experience quickly.

Armor: The armor itself is okay. No complaints…but for that big “Cyclops” eye on the helmet. My face kind of wrinkles up on that one.

Emblems: Decent emblems. I like the one immediately under the “PR” symbol. Kind of looks “Transformer-ish” and that’s a good thing to me.