I think the old bridge connects to the long bridge section near the wombats stadium near the memorial statue, which goes along and above the houses of the college campus and sororities disappearing far away in the mountains which can be seen from the gas station of east rosewood.
I caught this logical theory because if you ever drove the road of the old bridge to its end you'll notice the turn faces it back to rosewood on the level of the bridge.
I think the rest of bridges you see are just scenic additions for more realistic city which pretends to be surrounded by life elsewhere, not just restricted to the games driveable map.
Am I the only one who noticed that the inaccesible road going south out of Downtown Rockport is the turnpike? So does that mean the Turnpike existed BEFORE World? I always thought the Turnpike was only existant in World.