Being unfamiliar with Qld N/G Operations, why do they only run "short" Intermodals? Is it simply a case of running shorter more frequent services? Or is it a hangover from the past and they haven't brought them up to a more modern standard?
I am just trying to learn a bit more about Qld.
Primarily it's the infrastructure and the cost of modifying it. The North Coast Line is 1681km long, has 129 crossing loops and 198km of double track. Crossing loop lengths were largely established by the late 1960s and early 1970s when doubleheaded "90-tonne" 1310hp-1800hp locomotives established maximum train tonnages of around 1600-tonnes and train lengths of around 650m. Crossing loops were lengthened to suit this size train - most to around 700m - throughout the 1970s.
CTC infrastructure (now called RCS by QR) was then installed across the 104 crossing loops between Caboolture and Townsville between 1979 and 1992. Despite the introduction to the corridor of much more powerful electric locomotives in 1989 and diesels in 1995, QR mostly kept with the previous maximum train lengths, preferring the economies of replacing multiple locomotives on one train with a single locomotive, rather than running longer trains.
In the 1990s when other state operators began upgrading their single track interstate mainlines for 1500m trains, they were largely improving much less sophisticated infrastructure than that already installed in Queensland. The NSW North Coast Line had much shorter crossing loops to the equivalent QR line, which was already electrified with CTC installed at every loop to Townsville.
With the arrival of Open Access and then PN in 2005, the tonnages out of each of the major railing points - Rockhampton, Mackay, Townsville and Cairns - were effectively split, with each operator running a daily 650m long domestic intermodal service out of each of Mackay, Townsville and Cairns. As result the "short train" continued to work for each operator. Plus, not all intermodal is created equal. Aurizon's and now Linfox's export container trains from Mackay and Rockhampton are particualarly heavy and use shorter two-slot 80-tonne wagons - these trains can gross up to 3000-tonnes despite being restricted to 650m.
Fast forward to today with loop extensions now underway, PN and Linfox will probably lengthen their Cairns trains - #C49/#798 for Linfox and #CP1/#7P2 for PN - to 950m, potentially detaching 300m of train in Townsville, and allowing their Mackay and remaining Townsville loading to be combined into one train instead of running two. Alternativelly, hopefully corridor traffic growth will require the status quo for current services to be retained and the Cairns trains simply run extra length to handle growing tonnages. Time will tell.