The west span of the Bay Bridge connects San Francisco and Yerba Bunea Island. The bridge has two decks stacked on top of each other, and all of the cars on the bottom only get a view of the bridge above and the road ahead.
Which way should traffic on the upper deck go? It's an arbitrary decision. Or maybe not? In this case traffic flows into the city on the upper deck, so you get majestic sweeping views of the San Francisco skyline. This simple decision suggests that the city is more important than the island.