Derailment of Pacific National freight train 7MP5, Glenalta, South Australia

Executive summary

At approximately 1006 on 21 November 2004, Pacific National freight train 7MP5 derailed in the Adelaide Hills near Glenalta. Train 7MP5 consisted of four locomotives leading 72 freight platforms1 and wagons and was travelling from Melbourne to Adelaide on the Defined Interstate Rail Network (DIRN). The total train length was 1474m, with approximately 2960 tonnes trailing the locomotives.

The derailment occurred over a 3.7km section of standard gauge track between Belair and Glenalta, located approximately 23 to 19 kilometres from Adelaide respectively. The track exhibits a steep 1 in 45 down gradient with a series of 190- 350m radius curves, except for the standard gauge crossing loop located at Belair where the track is relatively straight with only a slight down gradient. Immediately adjacent to the DIRN is Adelaide’s broad gauge metropolitan passenger rail network.

Freight train 7MP5 had negotiated a 240m radius left hand curve that leads immediately into the Belair crossing loop at 42 km/hr, 8 km/hr below the posted speed limit. While access to the crossing loop was via a right hand turn-out, the straight ahead main line route had been selected over the facing points. The point of derailment occurred at the turn-out, where markings indicated that a wheel had ridden over the check-rail allowing the opposite wheel to travel up the wrong side of the Vee.

Freight train 7MP5 continued for approximately 3.7km, progressively derailing other bogies. At Glenalta the derailing bogies struck a concrete pedestrian crossing panel and the bitumen road edge of a level crossing causing the freight wagons to jack-knife. The impact at the level crossing alerted the locomotive drivers who immediately applied braking, finally stopping the locomotives and four platforms of the first 5-unit wagon, approximately 200m beyond the Glenalta station. The brakes on the remaining wagons applied automatically due to loss of brake air pressure. However, the gradient and momentum prevented the wagons from stopping before colliding (jack-knifing) with the wagons coupled immediately behind the locomotives. A total of 10 platforms and wagons were derailed, with five obstructing the passenger track and four coming to rest down an embankment into private residential properties.

While no person was injured, the potential for injury was high. The accident occurred adjacent to Adelaide’s operational metropolitan rail network with derailed vehicles causing significant damage to publicly accessible rail infrastructure such as pedestrian crossings, a passenger platform and a road level crossing. In addition, had metropolitan passenger trains been in the vicinity at the time of derailment, the risk of potential injury would have increased significantly.

The investigation determined that the most likely direct cause for the derailment of 7MP5 was significant wheel unloading as a wheel made contact with a check-rail at the entrance to the Belair crossing loop.

The investigation determined that a number of factors combined to contribute to this particular derailment. Any one factor in its own right is unlikely to have resulted in a derailment, but the four factors acting together greatly increased the likelihood of derailment.

• Wagon RQZY7066, with three empty platforms, was coupled immediately following the locomotives of 7MP5. Almost 2900 tonnes of trailing load was present behind the empty platforms, which exceeded the limit of 2600 tonnes stipulated by the Australian Code of Practice’s marshalling requirements.

• The use of dynamic braking as the sole means of controlling train speed on the descending grade exerted significant longitudinal compressive forces on the RQZY wagon with three empty platforms coupled immediately behind the locomotives.
• In tare condition, the RQZY wagon is relatively light weight, rides on very stiff vertical suspension, and exceeds the maximum constant contact side-bearer (CCSB) pre-load recommended by the ACOP. It is likely that the very stiff vertical suspension reduces the ability of an empty RQZY wagon to absorb discrete wheel impacts, such as the interface with a check-rail.
• Track geometry influenced the oscillating motion of rollingstock, causing the right hand wheel flange into rail contact as the left hand wheel came into contact with the check-rail. It is likely that track irregularities only served to influence the timing of this movement, such that peak lateral forces occurred as the wheel came into contact with the check-rail.

Safety actions have already been implemented by Pacific National. A review was conducted, and a revised procedure for loading and marshalling issued in December 2004.

The ATSB makes a number of additional recommendations relating to:

• procedures for train loading, marshalling and handling
• functionality of software management tools
• review of rollingstock design and performance acceptance requirements
• review of civil infrastructure design and maintenance requirements
• review of documented standards
• implementation and monitoring of safety actions.