05-03-2010, 12:11 PM
The preliminary report of the accident investigation committee has just been published. Here is what happened:
1) At the yards at Alnabru, there are two yards side by side. The hump yard consists of 5 A/D tracks (named A1-A5) north of (above) the hump, and 25 bowl tracks south of (below) the hump. The intermodal terminal consists of 5 A/D tracks along the eastern side of the bowl tracks (also below the hump), plus the container terminal parallel to the hump yard A/D tracks (not quite as high as the hump A/D tracks).
2) Over time, traffic in the hump yard has decreased, and traffic for the intermodal yard has increased. Also, most of the hump yard bowl tracks has been used for long term storage of cars. A practice had developed by which available capacity in the hump yard A/D tracks has been used for temporary storage for container cars.
3) On the day of the accident, a container train consisting of 15 cars arrived at 0310 hrs, and the containers were unloaded at the container terminal. At 0420 hours the containers had been unloaded, and the switching crew stashed the empty cars at in the hump yard terminal track A5 (at the top of the hump), where it was supposed to remain until the following evening, when a switcher engine would haul the cars down to the intermodal yard and then shove them into the container terminal for loading.
4) A little before 1 pm, about 8 1/2 hours later, a new switching crew requested a path to take their switcher (and one additional empty container car) to the north end of track A5 (ie the end furthest away from the hump). They got their permission, and took their switcher past the 15 stored cars before backing into track A5 from the north end, coupling the 16th car to the other 15. They then uncoupled from the 16 empty cars, expecting the cars to stay put, held by the track brakes.
5) Then the fatal error happened. The switching leader requested from the tower operator a path from A5 north down to track G5 in the intermodal yard. His intent was to run the switcher around the 16 empty cars and to go down to the intermodal yard to start processing a train that was inbound in track G4 of the intermodal yard.
For some reason, the tower operator made the assumption that the switching engine was still coupled to the north end of the 16 empty cars, and that he was requested to line the switches from the southern end of track A5 for a shoving move by the switcher pushing 16 cars down the hills to intermodal yard track G5.
6) The instructions for that move is that the route will not be laid until the switching crew confirms that they have the train under control. The tower operator ignored that part of his instructions, and laid the switches from A5 to G5. He then transferred his attention to other tasks (the inbound train in track G4).
7) The switching crew had their attention directed towards the north end of track A5, waiting for the clear signal. After about 2 minutes, the switching leader got back on the radio to check why he hadn't gotten his permission. He then sees that the 16 cars are heading down the hill from A5 into G5, and yells an alarm to the tower operators, who tries to activate track brakes to stop the train.
8) It is too late - the train is already heading downhill and gathering speed. If it had been directed into tracks G1, G2 or G3, it could have been diverted into a buffer at the south end of the yard. Tracks G4 and G5 does not have a way to direct the cars into a end track.
The accident has already happened - all that was left was desperate (and futile) attempts at derailing the train as it for 7 minutes were gaining speed going down the hill and into the harbor, before careening into the harbor area at 120 kph, killing three people on the ground.
9) Preliminary recommendations from the accident committee includes the obvious things - "use standardized message formats", "read messages back", "don't park cars on top of a hill without setting the hand brakes", "build a derail at the south end of tracks G4 and G5" and stuff like that.
10) In my opinion, the main reason for the accident was damned poor communication procedures between the switching leader and the tower operator, combined with the unfortunate practice of using the hump yard A/D tracks as overflow tracks for the container terminal.
The tower operator did not know what the switching leader was trying to do, so he made assumptions. Assumptions can be lethal.
Time will tell whether any of the personnel on duty will face criminal charges.
Stein
1) At the yards at Alnabru, there are two yards side by side. The hump yard consists of 5 A/D tracks (named A1-A5) north of (above) the hump, and 25 bowl tracks south of (below) the hump. The intermodal terminal consists of 5 A/D tracks along the eastern side of the bowl tracks (also below the hump), plus the container terminal parallel to the hump yard A/D tracks (not quite as high as the hump A/D tracks).
2) Over time, traffic in the hump yard has decreased, and traffic for the intermodal yard has increased. Also, most of the hump yard bowl tracks has been used for long term storage of cars. A practice had developed by which available capacity in the hump yard A/D tracks has been used for temporary storage for container cars.
3) On the day of the accident, a container train consisting of 15 cars arrived at 0310 hrs, and the containers were unloaded at the container terminal. At 0420 hours the containers had been unloaded, and the switching crew stashed the empty cars at in the hump yard terminal track A5 (at the top of the hump), where it was supposed to remain until the following evening, when a switcher engine would haul the cars down to the intermodal yard and then shove them into the container terminal for loading.
4) A little before 1 pm, about 8 1/2 hours later, a new switching crew requested a path to take their switcher (and one additional empty container car) to the north end of track A5 (ie the end furthest away from the hump). They got their permission, and took their switcher past the 15 stored cars before backing into track A5 from the north end, coupling the 16th car to the other 15. They then uncoupled from the 16 empty cars, expecting the cars to stay put, held by the track brakes.
5) Then the fatal error happened. The switching leader requested from the tower operator a path from A5 north down to track G5 in the intermodal yard. His intent was to run the switcher around the 16 empty cars and to go down to the intermodal yard to start processing a train that was inbound in track G4 of the intermodal yard.
For some reason, the tower operator made the assumption that the switching engine was still coupled to the north end of the 16 empty cars, and that he was requested to line the switches from the southern end of track A5 for a shoving move by the switcher pushing 16 cars down the hills to intermodal yard track G5.
6) The instructions for that move is that the route will not be laid until the switching crew confirms that they have the train under control. The tower operator ignored that part of his instructions, and laid the switches from A5 to G5. He then transferred his attention to other tasks (the inbound train in track G4).
7) The switching crew had their attention directed towards the north end of track A5, waiting for the clear signal. After about 2 minutes, the switching leader got back on the radio to check why he hadn't gotten his permission. He then sees that the 16 cars are heading down the hill from A5 into G5, and yells an alarm to the tower operators, who tries to activate track brakes to stop the train.
8) It is too late - the train is already heading downhill and gathering speed. If it had been directed into tracks G1, G2 or G3, it could have been diverted into a buffer at the south end of the yard. Tracks G4 and G5 does not have a way to direct the cars into a end track.
The accident has already happened - all that was left was desperate (and futile) attempts at derailing the train as it for 7 minutes were gaining speed going down the hill and into the harbor, before careening into the harbor area at 120 kph, killing three people on the ground.
9) Preliminary recommendations from the accident committee includes the obvious things - "use standardized message formats", "read messages back", "don't park cars on top of a hill without setting the hand brakes", "build a derail at the south end of tracks G4 and G5" and stuff like that.
10) In my opinion, the main reason for the accident was damned poor communication procedures between the switching leader and the tower operator, combined with the unfortunate practice of using the hump yard A/D tracks as overflow tracks for the container terminal.
The tower operator did not know what the switching leader was trying to do, so he made assumptions. Assumptions can be lethal.
Time will tell whether any of the personnel on duty will face criminal charges.
Stein