Inherent to the design of many dual gauge turnouts, is a region of reduced wheel rim contact on the broad gauge switch blade (rail head) through the transfer area. In circumstances where the switch blade is insufficiently restrained, and where the passing train has a narrow (127 mm) wheel rim width, there is an increased risk of derailment.
The ATSB is satisfied that the actions taken by the Office of National Rail Safety Regulator address this safety issue by encouraging all relevant rail service operators and rail infrastructure managers to note and consider the circumstances of the derailment outlined in this preliminary report. The ATSB acknowledges the additional action initiated by V/Line and will consider its adequacy as part of the ongoing investigation, the findings of which will be documented in the final report.
V/Line is currently actively managing the redesign, alteration and validation of the type 37 turnout to support restoration of standard gauge, 127 mm rim width, services.
Office of the National Rail Safety Regulator (ONRSR) – Safety Alert
The Office of the National Rail Safety Regulator has independently reviewed this occurrence and identified the higher risk of derailment through the wheel transfer area of some mixed and dual gauge turnouts for rolling stock having wheel rim widths of 127mm. ONRSR has issued an industry wide Safety Alert (RSA-2014-03).
While the ATSB is satisfied that the action proposed by V/Line will adequately address this safety issue in the context of type 37 turnouts, it is considered appropriate that all rail transport operators should be made broadly aware of the increased derailment risk in operating trains with narrow (127 mm) rimmed wheels through similar dual gauge turnouts.
The Australian Transport Safety Bureau encourages all relevant rail service operators and rail infrastructure managers to note the circumstances of the derailment outlined in this preliminary report, and to undertake an examination of all dual gauge turnouts under their control, to ensure that all authorised rolling stock can safely transition the turnouts.
