Not much I can say that's already been said by the other guys. You've got a great production, and a great atmosphere as a starting point. But that's kind of where this piece stays: a starting point. Now considering you're relatively new to the cinematic approach, and that you said this was more of an underscore than a dramatic scene, you've got the right idea. But because it's a mood of propulsion or a driving force as you mentioned, there's lots of room for it to evolve without it becoming an epic dynamic statement.
Perhaps a key change, or maybe just adding onto the 4-chord progression you've got going on; you could turn it into 6 or 8 chords as the track progresses, adding tension before shit hits the fan. Also, you could try piling on more heavy-handed instrumentation, such as a string bed and/or staccato buildup, as well as more percussion. With underscores, the goal is to play with the emotions and keep things interesting without having to go over-the-top.
I hope to hear more of this though; you're off to a great start!