Heavy Haul Rail in Australia

 
A large part of Rio Tinto’s global  iron ore mining activities are based in  the Pilbara region of north-west Western Australia where it operates 11 mines, three shipping terminals and the largest privately owned heavy haul railway in Australia.
 
Due to the vast distances between iron ore deposits and coastal sea ports mining companies need very long and efficient heavy haul rail infrastructure to move the ore from mine to shipping terminal.
 
Ansaldo STS has worked alongside Rio Tinto to deliver railway signalling and transportation solutions for its Pilbara operations for more than a decade.
 
 
A Signalling Challenge for a 400km Heavy Haul Railway
Ansaldo STS was first contracted by Rio Tinto in 1995 to deliver a new signalling system to ensure the safe and efficient delivery of iron ore from mine to port along 400km of Hamersley Iron’s dedicated heavy haul railway.
 
The trains that travelled the route were 2.4km long and weighed approximately 29,500 tonnes. To minimise the potential for damage that braking such heavy vehicles often causes, Ansaldo STS had to deliver a continuous system that would ensure that all heavy haul vehicles would not need to stop unless absolutely necessary. Given that the average cycle time was 33 hours and that each train was operated by a single driver, this was indeed a signalling challenge.
 
A Unique Solution
Ansaldo STS’s solution features an in-cab signalling system that incorporates a continuous onboard Automatic Train Protection braking system. This combination provides a system of continuous Automatic Train Protection based on a Limit of Authority, which is the maximum safe distance a train can travel.
 
The Automatic Train Protection braking system warns the driver if it appears likely that the train may exceed the speed restriction set. Should the driver fail to respond to the system’s warning, it will automatically apply the brakes.
 
Rails used in place of radio for vital communications
The trackside equipment uses distributed interlockings. It was developed based on the concept of using rails for vital communication in place of radio paths. A train can be guaranteed to stop in response to a break in the rails, whereas a train may continue to operate in the event of a radio system malfunction.
 
The system does not have lineside signals but is based on fixed block principles and functions as if there are signals present.
 
A series of track mounted transponders on board the train receives information on the positions of the various Limit of Authority locations. These transponders also advise details such as the gradient and speed restrictions that enable the Automatic Train Protection system to adjust the braking profile for the section of rail ahead.
 
The Automatic Train Protection system uses the block information from the transponders and the signal aspect from the rails to calculate the Limit of Authority and supervise the train operation accordingly. A data radio system on board the train immediately reports any attempt to breach a Limit of Authority or speed restriction to the train controller.
 
Automatic fall back mode in event of a control system failure.
Hamersley Iron also required Ansaldo STS to develop an automatic fall-back operation mode that would allow trains to continue under full interlocking control in the event of a control system failure.
 
Train controlled remotely when ore loading
During ore loading operations each train is driverless, and is controlled remotely by the ore load-out operator.
 
In this case the on board signalling system supervises a maximum speed and Limit of Authority to which the train is permitted to travel without a driver. The system enforces these instructions. Should the train attempt to breach any of these limits, the brakes will be applied and the train will stop.
 
Signalling supervision suspended indark territory
Some areas such as dark territory and yards are not equipped with the trackside systems. In these areas the signalling supervision is suspended by specially programmed track transponders. Speed limits are still supervised. A train re-entering an equipped area will detect the track transponders and will automatically resume signalling supervision.
 
Automatic downloads to wayside radio systems
The train downloads health data periodically to wayside radio systems which provide the controllers with real time alarms if the train’s performance is not within predetermined limits. The option is provided for the controller to schedule a train requiring maintenance into a siding to avoid disruption to following trains on single line sections.
 
Centralised train control system
A centralised train control system provides the controllers with network-wide automatic route setting, scheduling and conflict resolution capability.