Interesting concept with the bridge. While I do think i see what your trying to do with it, I think it just looks far too long and narrow. It seems as if most players would get knocked off or sniped really easily. It wouldn't be such a problem if there was an safer alternate route that isn't the cart track, but in general it seems like you need to close up that canyon a little more. Also, for those boxes on the bridge, you might want to add a little variety to them (oildrums, smaller boxes, etc...), as they seem just copy and pasted over and over.
Interesting idea, keep working at it.