This seems like a great idea that has could have its fair share of problems too, mainly with radio coverage. ITCS is a similar system that has been developed in the US and is still having problems after more then a decade of development. http://www.arema.org/eseries/scriptcontent/custom/e_arema/library/2007_Conference_Proceedings/Incremental_Train_Control_System_2007.pdf
To invest and piggyback on Telstra’s Next G network looks like a mistake, considering the experiences of this ITCS project. This PDF states they have changed from 900 MHz to 220 MHz to reduce drop outs in comms. Telstra uses 850 MHz for the Next G network. If problems do arise, Telstra won’t likely change their wavelength to something larger because they would loose too much speed with data transfer and this wavelength comprise provides adequate coverage for average telecommunications consumers as well as a small enough antenna size. It will be interesting to see how this trial is measured considering the relatively open terrain.
It also reduces redundancy to have a good majority of the countries Railway Signalling and Railway voice communications bundled with countries almost sole National mobile network. I’m guessing all of this will be as centralised as possible, again further reducing redundancy. The recent problem that brought a good part of Sydney to a standstill for hours when a central piece of control equipment failed, is a good example of the trade off and resultant redundancy loss from moving away from separate installations.
Other proven systems around the world such as ACSES on the North East corridor and SNCF’s system for the TGV utilise in cab signalling but use the rails for more reliable communications and still have the benefits of in cab signaling. In the TGV’s case, also allows for changing conditions of space between trains reducing headway. Track circuits are still used for detection providing the benefits of broken rail detection and sometimes other environmental conditions that could foul train movements. Using the existing rails for comms is surely cheaper then having to erect and maintain a separate radio network.
Adding more systems to better manage train movements can add safety to existing systems with track circuits at the same time such as the move to ECTS level 1 for RC and ATP used by QR. To remove track circuits for detection is taking away a long proven and relied upon safety measure. It is just cost saving and a way for infrastructure equipment companies to sell new products that essentially do the same thing but are not yet proven on large applications, not as reliable and not as safe as track circuits when not used in conjunction.
PTC is being mandated by the Government in the U.S for safety. Private companies there with massive networks have been reluctant to move to such systems due to cost and complexity even though the similar benefits of ATMS could be gained.
Also to compare air traffic to railways is poor in my opinion considering aircraft don’t have to remain on a physical route like trains have to but can avoid other aircraft in the open skies using Radar equipment on board. If radio guidance is wrongly given to a train from a remote location, no equipment at the location or equipment on board is going to give any indication of a problem ahead. The system is then relying on driver’s sight to detect a problem in time to possibly stop a train which could be a heavy freighter.