No filters were used. The tripod was placed near the stone wall that extends from the bridge so that it could be in view for visual context. This 30-second exposure allows for ambient light to evenly light darker areas of the bridge. The reflected bright spot in the middle of the span in the foreground is from a passing ship. I chose to keep this picture because of that unintended, yet beneficial side effect.
Good pictures are frequently a matter of luck.
Notice the star-like effect from the light in the middle of the picture. This is an artifact of the lens itself. Notice the same light on the next image that shows it with a mist filter.