Big Bayou Canot train disaster

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The Big Bayou Canot train disaster of September 22, 1993 is the worst disaster in the history of United States railroad company Amtrak. The accident claimed 47 lives, far exceeding the previous crash that held the title of Amtrak's deadliest, 1987's Chase, Maryland rail wreck.

The accident occurred after a CSX Transportation bridge over the Big Bayou Canot in southwestern Alabama (about 20 miles NE of Mobile, Alabama) was knocked out of alignment. When the scheduled Sunset Limited passenger train reached the bridge, first used by the route less than six months earlier, it derailed and plunged into the water. Forty-seven people were killed, many by drowning, others by fire.

The cause of the accident was determined to be a towboat, the Mauvilla, pushing several barges which collided with the bridge a short time before the disaster. One barge collided with a concrete pier, with no consequences. But another struck a swing span, and offset its end by nearly three feet. The span had actually been designed to rotate so that the bridge could be converted to a swing bridge by adding gears, a motor and control equipment. No such conversion had ever been done but the span had not been secured against sideways movement at its ends. The continuously welded rails did not break, thus preventing automatic shunting of stop signals. The Mauvilla had become disoriented in the area due to intense fog and did not realize that it had taken a wrong turn (into an un-navigable stretch of water) and struck the bridge.

The Sunset Limited struck the side wall of the swing span at full speed. The collision sent the locomotive flying, and in the ensuing chaos several cars fell into the water whilst the swing span disintegrated completely. The train had nearly full tanks of diesel, causing several fires to break out.

[edit] Analysis

A documentary on the National Geographic Channel, Seconds From Disaster, examined this accident in detail.

Although there were signals on the line operated by track circuits, the long welded rails did not break and shunt the signals to red. Ironically, had jointed rails still been fitted, the signals might well have dropped to red, as such rails would more likely have broken at the joints.
The span had actually been designed to rotate so that the bridge could be converted to a swing bridge by simply adding a motor and control equipment, if it was ever decided that boat traffic warranted this. No such conversion had ever been done and the span's lack of sideways rigidity had been forgotten.
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 "straps" to keep it in reasonable alignment with other spans of the bridge. Had such straps been fitted, the kink in the line might have been less severe and less 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. But the Big Bayou Canal is not navigable, so this seems nearly pointless.
Perhaps the bridge could have been protected by sacrificial piers, although the existing piers did not budge.
It is likely that the size and number of barges pushed by one tug had increased over time in excess of what the bridge could handle in a collision.
As a result of the accident, barge pilots are now required to be trained in the use of radar.

[edit] Similar accidents

The NTSB reported about 27 similar incidents involving bridge collisions.
December 24, 1953, Tangiwai disaster, New Zealand: 151 died when a bridge over the Whangaehu River collapsed. Trip wires now put the signals to red if the river level rises too high.
The Granville train disaster of 1977 involved a bridge collapse caused in part by inadequately protected and strapped piers and spans. Program to protect piers of other bridges instituted.
The Eschede train disaster, as seen on National Geographic cable TV, had flimsy piers like the Granville accident. Lessons from the Granville train disaster were apparently not put in place.
In New South Wales, a number of locations are fitted with landslip detectors that put the signals to red if a landslip is detected.
I-40 bridge disaster A barge collapsed a section of a bridge and several cars and trucks plunged into the Arkansas River.