A few years ago, an entire span of a busy eight-lane interstate bridge broke apart and fell into the Mississippi River in Minneapolis during rush hour traffic. Cars, concrete, twisted metal and people went crashing into the water.
When the dust settled, 13 were dead and more than 145 injured.
The bridge was Minnesota’s fifth busiest, carrying 140,000 vehicles each day. Eventually, the NTSB cited a design flaw – plus additional weight on the bridge at the time of the collapse – as the likely cause. It was one of the country’s worst infrastructure accidents in history.
When most people think of “forensics,” images of CSI and police dusting for fingerprints immediately come to mind. But do you also think of accident reconstruction and lasers?
In 2007, at the time of the bridge collapse, our firm was one of the first to use 3D laser scanning technology. When we heard about the bridge, we made some calls to the local authorities and offered our scanning services. The response was very positive. (Because of the magnitude of the disaster, the FBI ended-up scanning the site.)
The advantage and need for laser scanning in a case like this is to preserve the scene exactly as it is. On that evening in Minneapolis, the scene was changing, literally, as the rescue was taking place.
Cars were being checked and retrieved, pieces of the bridge were being moved, and all of this was taking place in a river. The precision of high-definition laser scanning and the ability to stay out of the way of first responders and rescue teams was very important.
Once scanned, the data files and photos of the scene could be sent directly to forensic engineers, the Department of Transportation, structural experts, bridge experts and many other engineers and contractors to begin collaborating on the information and building 3D computer models and animation.
Reconstruction is a critical because understanding how the bridge landed could be an excellent predictor of how it originally fell, which could lead to the point of the initial failure and ultimate collapse.
Unfortunately, these types of structural accidents happen all of the time. Recently, there have been several events here in Atlanta where this 3D scanning technology was used or could have been used.
Remember the bus accident on I-75 at Northside Drive, also in 2007? Six were killed when the bus carrying the Bluffton University baseball team tumbled over the highway overpass and hit the ground 30 feet below. The scene was scanned to run a simulation of what might have happened. Investigators later determined that the driver mistook the exit ramp for a lane and went into the curve at full speed.
Or what about the collapse of the elevated pedestrian bridge at the Atlanta Botanical Gardens in 2008 that killed one and injured 18? This is another example of a site similar to the Minneapolis bridge collapse, but on a much smaller scale.
Another example was when a 170-foot section of the railing and fencing along Atlanta’s 17th Street Bridge came loose and crashed to the interstate below in 2011.
All of these are good examples of where 3D laser scanning technology was (or could have been) an excellent choice.
Tate Jones has over 40 years of experience in land and aerial surveying and was one of the country’s earliest adopters of 3D laser scanning technology. A nationally recognized expert in the field of 3D data capture, he has worked with hundreds of clients in the forensic engineering, law enforcement, criminal defense, architectural and construction industries. Contact him at tjones@3DForensicScans.com.