There are lots of variations to truck combinations and it can get complicated, especially for farmer’s who only ‘moonlight’ as a truckie during harvest or seeding and then move on to all the other regulations we deal with.
The GCM is the gross combination mass:
tare of your truck (or prime mover) + tare of trailer + any fuel on board + the load you are carrying = GCM
Your combination ‘tare’ will rise and fall slightly with the amount of fuel you have on board.
- General Mass Limits (GCM)
- Concessional Mass Limits (CML)
- Higher Mass Limits (HML)
If you have or want to consider one of the ‘Dog’ combinations, they vary with extra tonnage allowances, so you will need to look into that further with the NHVR or consult a Heavy Vehicle Auditor for advice.
For an example, our Quad Dog Truck & Trailer Combination can run to a GCM of 49.5 tonne because we are in Maintenance Accreditation and the drawbar length had to meet a certain criteria for this. Because this combination is 19m, we are deemed a ‘general access’ route vehicle.
There is a permit still available as far as I know for a Super Dog, which allows you to load to a GCM of 48 tonnes, but there are speed restrictions you must keep to or you are in breach of the permit .
For an explanation of the 5% overloading tolerance, see my post:https://www.broadacrefarmsafety.com.au/grain-cartage-what-is-the-5-tolerance/