The bridge at Big Bayou Canot was not a swing bridge. It was a fixed bridge that got hit by a barge.
(OT) Well, kinda-sorta--it was
built so it could be converted to a swing span, but never equipped with the machinery to make it so. It was also never secured against unintended movement--the only thing holding it straight was gravity, so when the barge hit it, the end of the span slid sideways on its footings.
It is amazing the things that grivity holds in place on this planet. Regardless of what sort to devices had been or had not been put in place, the bridge
would not have stayed in place when hit by a barge. And, yes I have seen seconds from disaster. I have also read the NTSB repport. While there are many good and useful things in teh NTSB reports, the major portaion of which is a thorough detailing of what actually happened, IMHO some of their recommendations border on demanding protection from chunks of falling sky. It is not without reason that they have the authority to analyze and recommend, but not the authority to compel.
Here are my thought on the things said in Seconds from Disaster:
Although there were signals on the line operated by track circuits, the long welded rails did not break and did not cause the bridge approach signal to change to red. Had jointed rails still been fitted, the signal may have dropped to red, as such rails would more likely have broken at the joints.
Pure suppositon. It is just as likely that jointed rail would have heeld together. Plus, if I recall correctly the train had passed the last signal in advance of the bridge, so even if the signal had dropped to red the engineer was past the point where he could see it. Also once past the signal, the train itself shunts the circuit so teh signal would be red anyway.
The span had actually been designed to rotate so that the bridge could be converted to a swing bridge by installing a motor and control equipment, if it were ever decided that barge traffic warranted this. No such conversion had ever been done and the span's lack of lateral rigidity was a contributing factor to the accident.
This statement is pure suppositon not backed up by any form of analysis and is therefore of no significance. To even rate discussion, there should be development of a force analysis that would include force applied by the barge, the normal strength of the bridge bearings against lateral force, and the strength of the lower chord of the bridge against lateral bending. Anything less is simply arm waving and hollering.
One span of the bridge was pushed so far out of position that the kink in the line caused the derailment. The span was not fitted with "stops" to keep it in reasonable alignment with other spans of the bridge. Had such stops been fitted, the kink in the line might have been less severe and less dangerous.
Note the
"might" in this statement. Again, offered without analysis or proof. No response made because ther is no substance in the statemetn ot respond to. While it a pronouncement from the Bureau of the Blooming Obvious that the kink in the line caused the derailment, there was nothing in the analysis to suggest at what point the kink might become dangerous nor the point beyond which it was certainly dangerous.
Had barge traffic posed a regular hazard, special barge collision detection circuits could have been fitted to shunt the signals to red in case of a collision. Similar circuits are used to detect Washaways. But the Big Bayou Canot is not navigable, so this seemed nearly pointless.
True, adn the point is? how far should we go with this sort of stuff? At what point are we having dentists on call in case our chicken's teeth get a cavity?
