After a tram derailed on the Nottingham tram system last year, the Rail Accident Investigation Branch has released its report into the incident.
The details come a southbound tram was travelling at around 25mph at around 5pm on 12th June, when it approached an unsafe set of points at the north end of the Bulwell stop. The bogies on the tram were subsequently sent in different directions and the tram was derailed.
The report said that the tram then struck a pole supporting the overhead line equipment, causing a pane of glass to dislodge and strike a passenger, resulting in minor injuries. The driver of the tram also suffered a minor injury. Significant damage was caused to the tram and infrastructure, with the line reopening several days later on 23rd June following extensive repairs.
The investigation concluded that the spring-loaded points were unsafe having not been previously reset correctly after the passage of two previous northbound trams. The report said that whilst this could happen under normal working conditions, the risk at the time of the incident had "possibly been increased due to the environmental conditions causing the slide plates to be dry or contaminated."
A visual indicator located alongside the points, which was showing that the points were not in the correct position, was not observed by the tram’s driver. The driver believed that they would be informed if there were any issues with a set of points but had not been so on this occasion, was considered to have likely become conditioned to there being no issues at this location and was also possibly distracted.
RAIB’s investigation found that Nottingham Trams Limited did not have an effective policy in place to inform drivers of points failures and had not specifically assessed the risk of a driver incorrectly passing a lineside indicator. RAIB also observed that the process Nottingham Trams Limited used when introducing a new system to the tram fleet had not considered the effect the change may have on its tram drivers.
The report highlighted three recommendations, all of which were addressed to the operator. The first recommends a review of control room policy and procedures to ensure that clear and practical guidance is available to manage the response to engineering faults. The second recommendation relates to the improvement of risk assessments in light of this accident. The third recommendation concerns the consideration of human factors when assessing the effects of a proposed engineering change.
RAIB has also identified a learning point to remind tram drivers to not make assumptions about the status of signals or indicators based on their previous experience.