Another update. The picture of what happened (or at least - the picture you get through the media reports) is now fairly clear. Bear in mind that the reporters may have misunderstood some things - very few reporters have any clue whatsoever about how a railroad works.
The cut of 16 cars that ran away was initially located
above the hump of the yard, at the north end of the yard, in arrival/departure track A5 (se overview picture below):
Here is a closeup of the area around the hump:
And here is a second closeup that shows the situation on the north side of the tower more clearly - observe that the orientation of the last picture is such that north is left, and south is right:
A switcher engine, working from the north end of the yard had just added a 16th car to a cut of 15 cars on A/D track 5, just above the hump. The cars were held in position not by having their own brakes applied, but by track brakes - having their wheels pressed against the tracks by hydraulic operated brakes along the side of the track, controlled from the tower.
As far as anyone can tell, the last car was added to the cut in the proper way (given our type of couplers), with one guy on the engine and one guy going between the cars and hooking the car to the other 15 cars, before the engine moved away.
Some time after the 16th car was added, the track brakes holding the string of 16 cars, was released, and the cars started drifting down the track past the control tower.
Would not have been a big problem, except for a series of unfortunate choices having been made previously:
- the tower operator could not slow down or stop the cars using the hump retarders, because the switch closest to track A5 had been lined for the engine bypass track along the side of the yard, rather than for the hump. By the time it was realized that the cars were not being pushed by an engine, but rather was rolling away on their own, they were past the switch and on the engine bypass track, that runs the length of the yard.
No track brakes or retarders on the engine bypass track. Safety mechanism on that track is cutting the power to the overhead catenary wire, which doesn't do squat for stuff that isn't electric engines. So the cars were rolling down hump hill and along the side of the yard.
At the south end of the yard, they should have been caught by the trap - switches should normally be lined for a single ended track that goes straight ahead and ends in a couple of concrete blocks or a pile of gravel. Switches should only be lined for one of the freight tracks out of the yard if there is a train about to depart or arrive.
Those switches were lined for the freight track that goes downhill to the left, not for the trap or for the freight track that goes straight or slightly uphill to the right at the south end of the yard.
There now was a runaway cut of cars on the freight track. The accident had already happened - only thing left was the crash.
The people at central traffic control made two attempts to stop the cars that were picking up speed heading down the 2.5% grade down towards downtown and the harbor.
They first lined a switch about 2 1/2 miles down the track for a single ended spur that ended up in a cliff, but by the time the cars got there they were moving too fast, and just ran straight ahead through the switch instead of taking the deviating path into the siding.
About a mile further down a track block was activated, pulling a steel bar across the rails. The runaway cars hit that block at a speed probably exceeding 100 kph, and shattered it - pieces of the steel bar mechanism was found 90 yards away from the point of impact.
The cars then continued through the small yard at Loenga.
A decision was made to not divert the cars into Oslo Central station or into the southbound main - the risk of hitting passenger trains was deemed to big.
In the meantime, other people at the central traffic control had frantically called the police emergency number, which called the harbor office to warn them.
The people at the harbor office was still on the phone with the police by the time the cars careened into the harbor area, moving at speeds exceeding 100 kph. There were no routine for sounding a "take cover" alarm all over the harbor.
So the people less than a mile from the impact at that point had no chance to get warned in the 30 seconds or so that was left until the crash. Three people were killed - one in a car that was crossing the tracks when it was impacted by the moving cut of cars, two in a container transload facility were the office was smashed by the runaway cars.
Well, now we know roughly what happened.
What we still don't know is
why it happened - why the switches was lined as they were, bypassing the normal safety mechanisms, when the track brakes holding the cars were released.
No word yet on whether the operator on duty will face charges of manslaughter.
In these cases it is always hard to know exactly where you need to draw the line on personal responsibility versus designing the system so that the consequences of operator error is minimized. Because operator error
will happen - nobody has yet designed a human being that never makes mistakes.
No matter whether that operator will be charged or not, he or she will have to live with the knowledge that whatever was done with the switches and with the track brakes in the end killed three people, left one critically wounded and two seriously wounded.
I guess we will just have to leave that question of whether to charge the operator to the proper authorities.
The important thing is to try to prevent it from happening again. No doubt there will be changes made in operating practices at the yard
immediately.
Obvious technical changes would be maybe making it necessary for an outbound train to trip a signal at the south end of the yard, and then stop and wait for a timer circuit before the exit switch at the south end of the yard can be thrown to allow the train out of the yard or some such thing.
There perhaps should be found a good way of automatically returning the exit switches to the trap position after the last outbound car has passed over the switch, and
not returning the exit switches to the trap position right in front of an inbound train coming up the 2.5% hill from the harbor.
Or at least sounding an audible alarm (which can
not easily be turned off by the operator) if the switches remain lined for the freight line instead of the trap for longer than the time it normally would take a train to enter or leave the yard at the south end.
Maybe they also need to make changes to the track configuration where the futile attempts of stopping the runaway cars was made - making the single ended spur go straight ahead and the main track take the deviating path through the turnout. If there is room to make those changes down there - it is a pretty cramped area.
But the most important thing would be to prevent cars from rolling out of the yard when out of control - i.e. to prevent the exit switches at the south end of the yard from being set for the harbor track when there is no train just arriving or departing.
EDIT: I was looking at the <!-- m --><a class="postlink" href="http://www.bing.com/maps">http://www.bing.com/maps</a><!-- m --> again, and realized that I probably have shown the wrong path for the runaway cars at the top of the hump.
Looking again at the south end of the yard, I now realize that the runaway cars could not have rolled down the bypass along the right side of the yard (closest to the yard tower) - there is no way that they could have rolled out on the harbor track that way. The right hand bypass goes either into the trap or on the freight track to Grorud.
So my labels for the A/D tracks must be wrong - A5 must be the track furthest from the yard tower, not the A/D track closest to the tower, and the runaway cars must have rolled down the bypass along the left side of the yard, on the opposite side of the bowl tracks from the tower.
Doesn't change much in how the accident happened - the cars should still have been caught by the trap at the south end, if the switches had been lined into the trap instead of towards the freight track down to the harbor.
Stein