A screenshot would be helpful to see exactly what you're referring to. The layer on that multipolygon relation was raised to level 4 in changeset 144170003, probably in an attempt to have it draw over the top of underlying roads but I believe roads *always* draw over the top of closed ways/multipolygons, which would ultimately be for clarity I would assume. Having the bridge's multipolygon draw over the top of roads underneath would hide them and ultimately drawing the roads is more important for the functionality of a map than drawing supporting structures around the roads. Some sections in this area (e.g. the lightrail) is drawn in a dashed line but it's a pretty messy workflow as roads have to be broken up and fragmented in overlapping sections just to draw them right, which causes a lot of inconsistency over time and maintenance overhead. If there's a better way to do it, do let us know (e.g. some parameterized way that tells an object to be covered wherever it intersects with another object - but I doubt it)!