Rail head and train wheel profiles

Rail head and train wheel profiles

Regular inspection and maintenance of rolling stock wheel and rail head profiles are critical in ensuring that profile geometries are correctly matched to ensure wear is minimised and vehicle dynamics and performance are optimal.

Profile measurements of all wheels on accident train T842 and both rails at 10 locations over a section of about 1 km of track between Ormiston and Cleveland stations were conducted using ‘MiniProf’ wheel and rail profile measuring instruments¹³. The rail profiles were taken at specific points on the track leading into and through the region where the driver made applications of the brake to slow train T842 immediately before the Cleveland station (Figure ).

These measurements were taken to determine if the wheel and rail profiles, and the positioning of the contact patch between the wheels and rails, was compliant with rolling stock and network engineering standards and specifications. With the assistance of Computer Aided Design (CAD) software, MiniProf profiles of the wheels were overlayed onto the MiniProf rail profiles and aligned at the contact patch regions.

Figure : Leading passenger car 5173 wheel profiles and rail profiles at specific locations on approach to Cleveland station

The investigation found that although the rolling stock wheel and rail head profiles showed a very small amount of wear, both were compliant with Queensland Rail engineering standards and specifications. It was concluded that the profile condition of these components and the tracking of the wheels/bogies were unlikely have contributed to the wheel slide experienced by train T842 near Cleveland on 31 January 2013.

Train driver

The driver of train T842 had been employed as a train driver for 20 years with current training and route knowledge competencies to operate trains on the Brisbane Suburban Area Network. The driver had been assessed as fit for duty in accordance with the requirements of the National Standard for Health Assessment of Rail Safety Workers.

Following the collision the train driver was tested for blood alcohol content. This test returned a negative result. There was no indication that the driver’s performance was affected by physical, medical or cognitive factors.

Driver’s actions

On the morning of the collision, the driver of train T842 approached Ormiston station at a reduced speed following advice that previous trains had encountered difficulty in stopping. He did not encounter difficulty in stopping the train at Ormiston although there was some indication of a minor wheel slide near the end of the stopping sequence. Following the departure from Ormiston station there was no indication of any wheel slip, indicating to the driver that the there was sufficient adhesion. The track in this locality was dry and while overcast, there was no sign of rain.

The train departed for Cleveland station on the final section and was operated in accordance with the conditions that were known to the driver when departing Ormiston station. On the downhill section of track prior to Cleveland station the driver encountered localised light rainfall. This event coincided with the driver applying the train brakes on the initial setting, following the standard procedure and his training, to commence reducing the train speed for the 25 km/h points located immediately prior to the Cleveland station platform.

The subsequent excessive wheel slide that occurred saw the driver faced with the decision of reducing the brake application to control the wheel slide in an effort to enhance the braking effort, knowing that the speed of the train was not reducing as expected. The act of reducing the amount of brake application may have controlled the wheel slide but there was nothing to support the assumption that better braking was going to be achieved. The action of reducing braking effort was also counter intuitive, with the driver tasked to slow and stop the train on the Cleveland station platform before colliding with the buffer stop. In accordance with the recommendations provided in his training in relation to prolonged wheel slide events, when all other actions to slow the train had proved futile, the driver then made an emergency brake application.

Review of the train driver’s actions on approach to Cleveland station with respect to speed and braking indicates that they were consistent with sound driving practice and did not contribute to the accident.

Train information

Queensland Rail currently operates 28 Interurban Multiple Unit (IMU) 160 class electric trains, numbered 161 to 188 and 36 Suburban Multiple Unit (SMU) 260 class electric trains, numbered 261 to 296. Each IMU160 and SMU260 unit consists of two driving motor cars (DM car) coupled to either end of a non-powered trailer car (T-car), to form the typical set configuration of DMA – T car - DMB. The IMU160 and SMU260 class trains are similar in construction and operation, with the addition of a passenger toilet facility in the IMU160. The IMU160 and SMU260 class electric trains were constructed by a Downer EDI Rail/Bombardier Transportation Australia joint venture and progressively delivered to Queensland Rail between 2004 and 2011.

In service, the IMU160 or SMU260 configuration typically operate either as a single 3-car set or coupled with another set to form a 6-car train. The tare weight for each configuration is 128.2 t and 256.4 t respectively. At the time of the occurrence two 3-car sets (IMU173 and IMU180) were coupled to form train T842 (Figure ). IMU 173 and IMU180 were delivered to Queensland Rail on 5 February 2008 and 17 June 2010 respectively.

Figure : Train T842 configuration

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