The RAIB have concluded that a driver of a tram in Sheffield who approached Middlewood terminus on 19th July 2018 at a too high a speed – causing injuries to two passengers and a door to open slightly – had lost awareness of where he was on the line as they release their latest investigation report. The tram was travelling at over double the permitted line speed on the curve leading to the terminus when the incident happened.
The tram involved was 117 which was approaching Middlewood at 1558. The line speed of the curve leading to the terminus is 10mph but the tram was travelling at 23mph. The tram driver did realise he was going too fast just before the tram reached the curve and applied the emergency brake which brought the tram to a stand. Because of the speed of the tram entering the curve passengers were subject to excessive lateral accelerations with one passenger suffering significant injury when she was thrown from her feet and collided with a door. The impact also caused a component in the door system to fail and the door partially opened. The RAIB report also states that another passenger suffered minor injuries.
The report has concluded that the driver had lost awareness (although there is no evidence to suggest he fell asleep or was fatigued) of where the tram was in relation to the curve and as such he had not started to reduce the speed of the tram progressively to reach the 10mph limit of the curve. There was only a warning at the start of the curve of the limit with no previous markers to remind the driver. However, since this incident Stagecoach Supertram has implemented a step down speed restriction of 20mph 100 metres before the start of the curve. A further similar curve has also been identified and a similar step-down restriction has been implemented there as well.
The impact of the passenger being thrown against the door caused the door to become slightly open. This has been put down to fact that the connection between the ball joint and the vertical shaft fractured. This in turn meant there was a disconnection between the vertical rotating shaft and its corresponding door leaf from the locking mechanism which meant the door was free to open.
Since this incident Stagecoach Supertram have commenced a programme to check the conditions of all ball joints and work is also underway to develop an alternative design.
* The full Safety Digest on this incident is available on the RAIB website.