By Kim Smiley
On the evening of January 19, 2015, an overpass on Interstate 75 near Cincinnati collapsed, killing one and injuring another. The overpass was undergoing construction when it unexpectedly collapsed onto the road below it, which was still open to traffic.
This incident can be analyzed by building a Cause Map, a visual root cause analysis, to intuitively lay out the many causes that contributed to an accident by showing the cause-and-effect relationships. Understanding all the causes that played a role, as opposed to focusing on a single root cause, expands the potential solutions that can be considered and can lead to better problem prevention. A Cause Map is built by asking “why” questions and documenting the answers.
In this example, a construction worker was operating an excavator on the overpass when it collapsed. When the bridge collapsed the worker was crushed by the steel beams he was moving. The additional weight of evacuator and steel beams on the overpass likely contributed to the collapse. The overpass was being demolished as part of a project to remake this section of the Interstate and a portion of the overpass had already been removed. The work that had been done appears to have made the structure of the bridge unstable, but the construction company was not aware of the potential danger so the worker was operating on top of the overpass and the road beneath it was still open to traffic.
A truck driver traveling under the overpass at the time of collapse suffered only minor injuries, but came within inches of being crushed by the bridge. It really was simple luck that no other vehicles were involved. Had the collapse happened earlier in the day when there was more traffic, the number of fatalities may very well have been higher. As investigators review this accident, one of the things they will need to review is the fact that the road below the bridge was open to traffic at the time of the collapse. An additional relevant piece of information is that the construction company had financial incentives to keep the road open as much as possible because they would be fined for any amount of time that traffic was disrupted.
In addition to the safety impacts of this accident, the overpass collapse dramatically impacted traffic on a busy road with an estimated 200,000 vehicles traveling on it daily. It took nearly a day to get all lanes of the interstate cleaned up and reopened to traffic. No one wants to close roads unnecessarily and the goal of minimizing traffic is an excellent one, but it has to be balanced with safety. The collapse of the overpass wasn’t an unforeseeable random accident and the demolition needs to be done in a safe manner.