Report on abnormal signal observation at Atna station Rørosbanen 6 January 2015
Railway report 2016/01
At 17:57 on Tuesday 6 January 2015, the driver and the head conductor of train 2387 observed an abnormal signal at Atna station on the Røros line. The driver and head conductor have explainedthat they saw that the main departure signal N was green (proceed) for a period of around ten seconds, at the same time that the pre-signal for this signal showed 'expect stop' and the informationin the driver's cab showed 'expect stop'. During this period, an oncoming train was on its way to Atna from the opposite direction, from Hanestad.
The incident itself did not lead to a dangerous situation, because, as was explained, the signal that showed green went back to red before train 2387 had reached the platform at Atna station.
However, the logs from the signalling system did not show the same situation as described by the driver and the head conductor. According to the log, the signalling system worked as intended, and the log states that the signal was red during the period in which it was reported as being green.
As the driver and the head conductor were certain about their observations of an incorrect green light, this has led to uncertainty concerning the safety function of the signalling system. The Accident Investigation Board Norway (AIBN) has therefore conducted a series of checks in order to find an explanation for the observation.
A comprehensive review of the documentation and analyses of the NSB-87 signalling system have been carried out, in addition to inspections and tests of the signalling system at Atna. This is described in the report and pertaining appendices.
There are four main theories that may explain the incident: an optical illusion that resembled a green light, sabotage, human error in the form of misinterpretation, or a technical fault in the signalling system. It is the technical element of the signalling system that has been the main focus of this investigation.
The AIBN has not found any basis in the documentation or the tests conducted that can explain the situation described by the driver and the head conductor. All the tests conducted have shown that the signalling system works as intended.
The driver and the head conductor are certain about their observations, and this has weighed heavily in this investigation. The AIBN cannot say for certain what caused the ambiguous signal observed by the driver and the head conductor of train 2387 at Atna station on 6 January 2015.
This report is in Norwegian only. English summary is included.
No safety recommendation is issued in connection with this investigation.
Facts
| Location | Atna station |
| Occurrence date | 06.01.2015 |
| Train No | 2387 |
| Type of Transportation | Passenger train |
| Type of occurrence | Wrong side signaling |
| Rolling Stock | Multippel Unit (MU) |