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>> “ I cannot understand not closing the roadway during the bridge installation and testing.” <<
They were the low bidders!
OK, Money is usually the answer to a management trying to get ahead by skipping obvious safety precautions, but in this case I suspect that they will determine that laws were also broken by this lamebrained move to leave traffic on the highway.
When the Highway Patrol needs to remove debris from the road way, they often completely stop traffic.
It is not enough to say it costs too much to stop traffic for a while, they could easily have told the city that this was their (the city’s) responsibility. The city would have to manage without the roadway for a few days, and the cost to the project management should not be affected.
The risk of a collapse was probably considered very low, but was highest during the first few hours when testing and re-tensioning the stress cables. The severity of a collapse was not too severe if traffic was restricted from using the roadway, but with cars under the structure the severity was astronomical. This was not a hard call for a reasoning manager to make.