, but I can't get its document links to work. However, the two main reports (with lots of pictures, and considerably more German words) are
We already knew the underlying cause from the prosecution of the signaller. This adds details of the system in use, and all the ways it could have been better from the point of view of avoiding the mistake and then preventing the accident.
At 06:47 (local time) on 9 February 2016, two passenger services collided at around 150 km/h (90mph) on a curve on the single line between crossing points at Bad Aibling and Kolbermoor.
One train derailed and several of its carriages overturned.
Eleven people were killed (7 passengers and 4 members of staff, including both drivers).
Of the 89 injured, 26 were seriously hurt.
The German NIB determined that that immediate cause of the event was signaller error. The signaller completed his training on 16 January 1997, qualifying to signal Bad Aibling specifically later that year. Per his roster, he had been working at Bad Aibling, Bruckmühl and Westerham. On the day of the accident, he started work at 04:45 at Bad Aibling, his last shift (at Bruckmühl) having finished at 14:40 the previous afternoon. It was considered that the ‘required minimum rest’ had been ‘respected’.
Although the signaller had been trained to use
GSM-R▸ , the German NIB noted that the specifications for ‘establishing an emergency call connection and delivering an emergency stop order’ are incomplete. Specifically, there is ‘no distinction between emergency call train radio and emergency call route’. It was found that the former had been carried out for the last time on 15 September 2015. The implication is that – at the signaller’s last ‘refresher’ – the emergency call route function ‘was probably discussed, but not practiced’. The NIB pointed out that training exercises ‘take place in the relaxed atmosphere of a training course and not under the stress of a pending irregularity or a dangerous event in the railway operation’. The signaller had never had to make such a call in the field, and – as the NIB also clarified – ‘the likelihood of confusion between the two emergency call types is too high, especially under stress’.
On 12 April 2016, it was reported that the signaller had been arrested, as prosecutors suspect he was distracted by playing a game on his mobile phone at the time of the incident. This led him to make a signalling error, and then – in a state of some distress – dial the wrong emergency number (in fact altering all station staff along the line instead of the driver of the oncoming train). His second – correct – emergency message came too late to prevent the accident.
The game in question was ‘Dungeon Hunter 5’, which the signaller allegedly played with some regularity, even though this is prohibited during working hours. Analysis of his phone records show that his mobile use often corresponded with his working hours. Indeed, the NIB notes that the signaller’s ‘last active usage was at 06:40:47’ (ie, just over six minutes before the collision and after some 22 minutes of play). At this point, one passenger train had entered the Bad Aibling section, while the other had come to a stand at Kolbermoor. The signaller’s phone was not used again during subsequent events.
The investigation report also explains how – in the criminal case against the signaller – the subject of online gaming was discussed by an expert witness, who noted the following:
The total duration and frequency of the signaller’s gaming actions had increased significantly since 1 January 2016
The ‘proportion of playing time in working hours [was] 72%’
‘It is highly probable that simultaneous use of the computer game resulted in decreased cognitive resource allocation for the operational tasks (impairment of cognitive attention, memory and executive function, with an intense computer game continuing to linger for some time).’
Thus, ‘it can be assumed that’ the online game ‘directly contributed’ to the signaller’s error. That is, instead of allowing the trains to cross in Kolbermoor, he allowed the train at that station to enter the single line en route to Bad Aibling. He ‘looked but failed to see’ the indications on the panel showing the actual positions and routes of the trains involve. It did not help that the occupation of the single line (the signalling panel in question replacing a string of yellow route-setting lights with a single red ‘occupied’ light) was too easy to overlook.
The signaller had used a Zs-1 ‘ersatzsignal’ signal, which is not interlocked and can give authority to pass a stop signal showing danger when the main aspect cannot be cleared. Unlike the PoSA (proceed on sight aspect) signals in
GB▸ , it does not confirm the existence of a wheeled path to the end of the section of line protected, and can be cleared irrespective of a route having been set in the opposite direction.
Writing in the November 2016
IRSE▸ News, Peter van der Mark noted that the Zs-1 ersatzsignal may only be used when the main aspect cannot show a proceed aspect for one or more of the following reasons:
A defective signal semaphore or bulb.
Defective point detection, but only after the turnout has been secured in the proper position.
A defect in the signalling block system (such as a cable fault), but only once it has been established that the line ahead is clear.
A proved clear track circuit that persistently shows ‘occupied’.
Once a Zs-1 ersatzsignal has been used, the train must travel at no more than 40 km/h (25mph) and be prepared to stop at any obstruction until the next relevant signal has been reached. When a starting signal displays a Zs-1 aspect, the train must keep to the 40-km/h rule until the train has reached the final set of points at the yard or station, after which 100 km/h is permissible. At Bad Aibling, the driver passed the Zs-1 and accelerated to 100 km/h after passing the last set of points and entering the single line section in accordance with the rules. However, the NIB noted that the ‘complexity of the rules is high’ and the rule book ‘is (under time pressure) not suitable as a reference work. The provisions to be applied are based on several directives and in different modules, sections or paragraphs.’
Action taken
The signaller was held in ‘pre-trial detention’ form 12 April 2016. The prosecutors brought the charges to the court in Traunstein in mid July 2016 with accusations on 12 counts of ‘murder by negligence’ and 89 accounts of ‘injury by negligence’. On 10 November – the first day of trial – the defendant confessed to the charges brought by the prosecutors, but his lawyer wanted the degree of guilt to be evaluated during the subsequent proceedings. The signaller showed a degree of compassion for the victims, he refused to answer questions on the intensity of his preoccupation with the mobile game.
The court ruled on 5 December 2016 that the signaller was guilty of all charges, and he was sentenced to three-and-a-half years in prison. He was released on probation in July 2018.
Recommendations
The ‘train radio emergency call’ and ‘emergency call route’ functions in the GSM-R selection menu should be combined such that they operate after a signaller has pressed the ‘emergency call button’ on the control panel
The signalling rules and regulations should be reviewed in full, with reference to an appropriate risk assessment
Simulators should more extensively in training, which should also address the issues portable media devices and distraction.
The use of the Zs-1 ersatzsignal should be subject to a risk-based reassessment.
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