My favorite point when I'm walking in to a bridge, where the bridge first becomes visible after the last curve. It's best, of course, to have the shortest possible bridge span over a waterway, perpendicular to the channel, usually. Since a rail route is not usually laid with that in mind, there is often a curve just before the bridge, to bring the tracks perpendicular to the stream channel, rails and ties being cheaper than bridge steel from Wisconsin Bridge & Iron.