The I-35W Bridge On Homecoming

The new I-35W Saint Anthony Falls Bridge features an innovative LED lighting system where each LED element is individually addressable, allowing any color in the spectrum to be displayed. On most nights, the bridge is bathed in a eerie blue glow that looks like something out of a science fiction movie. However, the bridge is occassionaly lit up in other colors for special occasions, but in this case, I have not yet learned what the special occasion was.

On October 21, 2011, I happened to drive past the I-35W bridge and noticed that the legs were lit up white rather than blue. On closer inspection, I found that the downstream side of the bridge was red. This isn't the first time that the bridge has been lit in a red, white, and blue scheme. For example, on September 11, 2011, the bridge was lit in alternating red, white, and blue stripes as a memorial on the tenth anniversary of the 9/11 terrorist attack. On June 26, 2009, the bridge was lit with the northern third and north main piers in blue, the middle third in red, and the southern third and south main bridge piers in white.

The mystery here is why the bridge was lit up in this scheme. There was no notice in the media. There were no national, military, or patriotic events happening that would have prompted a display. One possibility that I have considered is that this was the final day of a recent bridge maintenance project, so perhaps the lights were being tested as part of this maintenance. Another clue is that the upstream side of the bridge has been blue during other light displays, such as on Halloween. I have since learned that MN-DOT is keeping the upstream side that faces the Remembrance Garden memorial in blue as part of the memorial. As a result, the light scheme for this display was red over white, with the blue being part of the bridge memorial.

One major event that was happening in town over the weekend is homecoming at the University of Minnesota. The Gophers colors are maroon and gold. It is possible that this color scheme was intended to be the Gophers colors. Both maroon and gold are hard colors to create using additive colors such as the light provided by the LED system on the bridge. It is difficult to get dark colors like black when projecting bright light. The bright white surface of the bridge adds to the difficulty. It is possible that this was a close attempt at maroon and gold. However, the net effect ended up looking very much like the red team color worn by the Nebraska Cornhuskers, the Gopher's opponent in the Big 10 football game scheduled for the next morning.

The photo above, showing the red side of the bridge, is looking north across the Mississippi River along the downstream face of the structure from the south side of the West River Parkway. Note the small white segment at the center of the bridge. There is a small navigation light that hangs down under the bridge. That light would be lost in the bridge light display, so a short white segment was included to avoid obscuring the navigation light.

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This photo is the blue face of the bridge on the upstream side of the structure. The vantage point is a small clearing on the edge of the bluff along the sidewalk on West River Parkway. From this view, the bridge piers do look more gold than white, much closer to the gold color used by the Gophers than what we see in the top photo.

The photo above is the downstream east side of the south bridge abutment. The West River Parkway passes under the structure, along with a walking trail and a bicycle path, with downtown Minneapolis being visible in the background. The blue lights on the far side are not directly visible, but they do shine onto the embankment leading up to the abutment as well as the street. In fact, it appears that the blue light is a little brighter than the red light based on the amount of ground that is illuminated, however, that might be due to the white light under the northbound span washing out the red light.

This view is looking north across the river from the walking trail along the north side of West River Parkway as it passes under the bridge. The south main bridge piers are in the foreground, along with the south observation deck. From this angle, no red light is visible, and only two small areas of blue are showing.

This is a similar view to the photo above looking north across the Mississippi River, but from a vantage point located on the south observation deck. A line of LED light arrays are visible on each side of the bridge, with blue on the upstream side and red on the downstream side. The blue-green light between the bridge spans at the north abutment is the bridge monument located on top of the bridge deck. The north observation deck is not yet open to the public as this was written in the autumn of 2011.

This view of the red lights along the downstream face of the I-35W Saint Anthony Falls Bridge was taken from the sidewalk leading to the south observation deck.

This view of the blue lights along the upstream face of the I-35W Saint Anthony Falls Bridge was taken from the southwest corner of the south observation deck.

The main bridge piers are lit by a array of LED lights featuring three rows of bulbs. The array has green, red, and blue LED lamps, with nearly equal amounts of red and green plus a little less blue being mixed to create the slightly off-white color on the piers. There are 16 of these panels, with one on each side of each of the eight main bridge piers. They are located at the base of the piers and are incorporated into the grates that cover the drains.

The lights that run along the length of the bridge spans are made up of a single row of LED lamps. This is looking directly up at the downstream side of the bridge, where we see that the red light is composed almost exclusively of red light, with just a tiny amount of blue being added. The blue being mixed in adds weight to the theory that the color was intended to look maroon rather than red.

This photo is looking directly up towards the upstream side of the bridge, where we see a row of LED lamps showing the blue color. The red and green lamps are not used for this shade of blue. If you look close, you can see an electrical junction box located between the two light arrays, along with conduits connecting the box to the arrays.

This is another view of the downstream face of the structure lit up in red. The vantage point is the bicycle trail as it passes under the nearby 10th Avenue Bridge on the south side of the Mississippi River.

This is a closer view of the north main bridge piers from the same location on the bicycle trail as it passes under the 10th Avenue Bridge. A small amount of blue light is visible near the north bridge abutment. The green color to the left of the blue is a building in the background. The green color to the right of the blue is a reflection from the bridge monument that leaks down through the gap between the two bridge spans.

This view of the downstream side of the I-35W bridge is from a vantage point high above the river on the bluffs between the 1I-35W bridge and the nearby 10th Avenue Bridge. This gives a good view of the LED street lighting on the traffic decks. I have discovered that traffic in the far right northbound lane will light up the bridge railing. Since this photo was taken around midnight, I had to wait for a few minutes for several cars to be in the right lane at the right time to illuminate a majority of the bridge railing. This is a two second exposure at ISO100, and even at 55 miles per hour, a car doesn't cover that much distance in that amount of time.

This photo is a view looking downstream towards the blue side of the bridge. The vantage point is the main navigation span of the nearby Stone Arch Bridge. The Saint Anthony Falls Bridge is about one-half miles to the east of our of the camera location. The Lower Saint Anthony Falls Lock & Dam is located directly in front of the bridge, which slightly obstructs the view of the lower parts of the bridge piers.

This is a closer view of the main bridge span, seen from the same location on Stone Arch Bridge. most of the white reflections are from lights located on the lower falls Dam. The LED street lights on top of the bridge cast a broader shadow, of which, three are visible on the water.

This photo, also of the upstream blue face of the I-35W bridge, was taken from the entrance road to the west side of the Lower Saint Anthony Falls Lock & Dam. This road can be accessed from the parking area at Mill Ruins Park. There is a much better defined bridge reflection on the water at this location because we are much closer to the water elevation than we were on the Stone Arch Bridge.

This is a close view of the north main bridge piers from the same vantage point on the road leading to the upstream side of the lower dam. One gate of the lower dam, which is not lit up, is visible due to it partially blocking our view of the bridge piers.

These two photos are the same photo from the same location, but taken at two different exposure levels. The vantage point is looking towards downtown Minneapolis from Northern Pacific Bridge Number 9, an old railroad bridge that has been converted into a bicycle and pedestrian path crossing high over the Mississippi River. The photo above is a 2 second exposure that shows the bridge about how it looks to the naked eye. The 10th Avenue Bridge is partially blocking our view. The downtown buildings were not brightly lit up due to it being past midnight. The photo below has a 8 second exposure. While it overexposes the bridge, a ton of detail is revealed. For example, the building are well lit, the boat lock and lower dam are visible, and a blue reflection from the far side of the I-35W bridge is much better defined on the surface of the water.