Please note that some people may find some of the information in this article distressing
Yesterday the Rail Accident Investigation Branch published its second interim report into the tragic tram crash near Sandilands tram stop on 9th November.
You can view the full report here.
The key findings relating to the cause of the accident are as follows:
“A single 20 km/h (13 mph) speed restriction sign measuring 607 mm by 405 mm was located at the start of the curve. A tram approaching the Sandilands Junction area from Lloyd Park at 80 km/h (50 mph) would need to brake at its full service rate of 1.3 m/s2 approximately 180 metres before the speed restriction sign in order to be travelling at 20 km/h (13 mph) when the sign was reached. RAIB observations and measurements indicate that tram drivers approaching Sandilands Junction from the direction of the tunnel during the hours of darkness, in clear conditions, can sight the curve and read the speed restriction sign from around 90 metres with headlights on main beam, and from around 60 metres with dipped beam. The point at which the curve can be sighted and the sign becomes readable in clear conditions is therefore about 90-120 metres beyond the point at which a full service brake application must start in order to reduce speed from 80 km/h to 20 km/h (full service brake deceleration is around half emergency brake deceleration). At the time of the accident the readability of the speed restriction sign is likely to have been adversely affected by heavy rain. There was no sign to indicate to drivers where they should begin to apply the brake...they were expected to know this from their knowledge of the route”.
“The RAIB’s investigation to date has not indicated any malfunction of the tram’s braking system. Analysis of the tram’s On-Tram Data Recorder (OTDR) indicates that the service brake was not applied until around 2½ seconds before the tram reached the 20 km/h speed restriction sign. The tram’s speed had reduced from 78 km/h (49 mph) to 73 km/h (46 mph) by the time the tram passed the sign. The hazard brake was not used. The late application of the brakes, and the absence of emergency braking, suggests that the driver had lost awareness that he was approaching the tight, left-hand curve. The RAIB is continuing to investigate the factors that may have caused this to occur”.
London Trams introduced additional speed restrictions on the approach to Sandilands junction and at other locations before they resumed the service on 18th November 2016 and they have since installed chevron warning signs on the curve and on other similarly tight bends.
With regard to why the results of the crash were so serious:
“The RAIB’s initial examination of the tram indicates that its body structure and interior fittings remained largely intact, apart from the right-hand side windows and doors. The injuries to passengers were not therefore caused by loss of survival space as a result of deformation of the tram body, although impact with interior fittings is a possible cause of some injuries. Some windows on the right-hand side were broken and dislodged from the tram body. The windows in the body-side of the tram were made from 6 mm toughened glass and the windows in the doors were made of 4 mm toughened glass. All the windows were fitted with an anti-vandal film on their internal faces. Initial indications are that a number of passengers with fatal or serious injuries had been ejected, or partially ejected, from the tram through broken windows, both in the body-side and the doors. Of the seven passengers who died: one was found inside the tram; two were found partially inside the tram; three were found underneath the tram; and another was found on the track close to the tram. Work to understand the detailed sequence of events, and the means by which passengers received their injuries, is ongoing”.
Their investigation continues and includes consideration of:
- the sequence of events before and during the accident;
- events following the accident, including the emergency response and how passengers evacuated from the tram;
- the way in which the tram was being driven and any influencing factors, including the signage and other information presented to the driver;
- the design, configuration and condition of the infrastructure on this section of the route, including signage;
- the tram’s behaviour during the derailment and how people sustained their injuries including assessment of the way the tram overturned and its effect on passengers and understanding the behaviour of the tram windows;
- any previous over-speeding incidents on Croydon tramway;
- any relevant underlying management and regulatory factors including the management of the competence and fitness of staff; the risk management arrangements, including hazard identification and risk assessment throughout the life of the system; the accident and incident reporting regime, and investigation of previous events; and the monitoring and review of safety on the Croydon tramway (including the activities of Tram Operations Ltd, First Group, London Trams and Transport for London).
- the standards and design guidance used in the construction and maintenance of the Croydon tramway infrastructure, including their source and development;
- the standards applicable to the tram’s windows;
- the standards and design guidance used on tramways elsewhere in Europe (eg the German BOStrab standard) relating in particular to off-street running; and
- the differences between standards applied to trams and those applied to buses and trains.
I will keep you updated.