Over the years and even this year, economists have measured the road transport task in terms of net tonne kilometres (ntkms). This is a poor indicator of task when compared to the alternative measure being gross tonne kilometres (gtkms).
The following two case studies demonstrate this fact. Two truck types carry 90 tonnes over a trip distance of 90 kilometres. In case one, this task is undertaken by 90 3.5 tonne GVM small rigid trucks. In case two, one PBS ABB quad road train does the 90 kilometres trip carrying an equivalent 90 tonnes.
The difference in net tonne kilometres is zero. However, the difference of gross tonne kilometres is some 66 per cent. The cases are described below:
Case one:
A small two-axle Rigid truck (3.5T Tare and 4.5T GVM) carries one tonne per trip. The task is 90 trips, meaning its 4.5 tonnes multiplied by 90km trips and 90 trips in itself, equalling 36,450 gtkms. The net tonne kilometres is 90 net tkm.
Case two:
A large PBS ABB quad road train on HML (45.5 T tare) carries 90 tonnes on one trip. The task is 135.5 tonnes multiplied by 90km, equalling 12,195 gtkm and 90 net tkm.
The difference in net tkms between cases is zero! The difference in gross tkms between case one and case two is 24,255 Gtkms, with a percentage difference of 66.5 per cent.
Why do economists fixate on net tonne kilometres? It does not take into account productivity. Savings in gross tonne kilometres saves road pavement impacts, truck numbers on the road, community freight exposure, kilometres travelled, fuel consumption and driver resources.
Rail calculates task in gross tonne kilometres – why not so for heavy road freight vehicles? PBS trucks deliver these gtkm savings. Economists should have a rethink.