Overdue switch maintenance contributed to derailment in Hilversum
The intercity derailed when it passed a switch shortly after leaving Hilversum station. After the first section of the train had travelled in a straight direction over the switch, the rear section of the train was suddenly directed onto the adjacent track, as a result of which the train derailed. A train travelling in the opposite direction was brought to a standstill in time to avoid a collision. As the failure of a switch can result in a major accident, the Safety Board initiated an investigation.
The derailment was caused by a fatigue fracture in a small component (ring) of the switch. This fracture caused the switch to shift to an incorrect position when the train travelled over it. The fatigue fracture occurred as a result of finishing defects during the manufacture of the ring and the fact that the switch was in poor condition. Parts of the switch were so badly worn that the wheels of passing trains frequently scraped along the switch blade; known as ‘flange-back contact’. The fractured ring was not designed to be exposed to the additional forces resulting from these flange-back contacts. It became clear that flange-back contacts also occur at other switches in the Netherlands.
Maintenance and knowledge exchange
The Safety Board investigation revealed that the maintenance regulations imposed on contractors by ProRail were insufficient to prevent flange-back contacts. Moreover, ProRail had no knowledge of the worn condition of the switch. As a consequence, a heavily-used switch had become unsafe, without this situation being observed and dealt with.
Due to insufficient information exchange between ProRail, the supplier of the point machine and the maintenance contractors, the risk of such flange-back contact was not acknowledged. Furthermore, insufficient lessons were learned from two serious derailments in England involving the same problem. Based on those accidents, the rail companies could have known that flange-back contacts, even over a short period of time, can cause serious damage to a switch and must consequently be avoided.
Due to the increased pressure from a society that is demanding improved railway performance, maintenance has come to focus more on preventing disruptions. In its report, the Safety Board points out the risk of this development unintentionally coming at the expense of rail safety. If railway maintenance becomes too unilaterally focused on preventing train service disruptions it is possible that parts which are essential to safety are inadequately maintained, without this being noticed. The switch at which the derailment in Hilversum occurred is a clear example.
On the basis of its investigations, the Dutch Safety Board recommends that railway maintenance be organised in such a way that the safe usability of the railway infrastructure is more effectively guaranteed. The Safety Board addresses not only ProRail in this respect but also the other rail parties. The recommendations made concern both the way in which railway maintenance is managed and monitored and the way in which the companies involved share and utilise safety-relevant information. Furthermore, the Safety Board urges the State Secretary for Infrastructure and the Environment to ensure that the safe usability of railway infrastructure is granted sufficient weight in relation to other interests such as capacity and punctuality. The Safety Board requests that she integrates this vision in the current rethink of the policy framework for railway safety.