Tectonic: Thanks for picking that up, I totally agree . Those tubes you highlighted could be much simplier. I couldn't decide whether to left the holes in upper beams modeled or cut them with alpha and normal map. I should have tried to let the texture do it.
I think for game resolution 50k triangles might be a bit large. I've noticed some areas where you could cut down on polys a lot of your smaller tubes could be reduced in sides. on your white vehicle the upper beams could have the holes just normal mapped on instead of modeled.