A single GravWalk Block is 280-340 polygons (depending on the particular railing variant).
While the GravWalk is still getting pipe-lined into the game, Ive taken the liberty of making a Light Bridge block set, kind of like the ones found in the Halo Franchise. Both sets still need a bit of work to refine the textures, and the Light Bridge still needs construction stages modeled, as well as all the back end work. One Light Bridge emitter block sits just over 400 polygons though the bridge blocks themselves are only a single poly.
All in all I'm quite happy with how both are turning out, and Ill be sure to post both once they are in-game.