Mass, Dimension, and Load Restraint Limits
The core idea
Three separate regimes apply: mass limits, dimension limits, and load restraint. A load can be legal on one and illegal on another. Questions often combine them.
Concepts to master
- Mass limits: gross vehicle mass (GVM), gross combination mass (GCM), axle and axle-group limits, and steer-axle limits. Know that axle limits are not simply GVM divided by axle count.
- Dimension limits: width, height, length, and rear overhang. Exceeding them requires a permit and often pilot/escort vehicles.
- Load restraint: the load must be restrained so it cannot move under expected forces. Know the performance standard (the load must withstand forward, rearward, and lateral forces) and the methods: lashing, blocking, and containment.
- Load distribution: keep the centre of gravity low and centred; poor distribution overloads axles and destabilises handling.
- Documentation: consignment notes and permits must match the actual load.
Traps in questions
- Assuming a load under GVM is legal when an axle is overloaded.
- Forgetting rear overhang and height as separate limits.
- Treating restraint as "enough straps" rather than a force standard.
- Ignoring that load shift changes axle loads dynamically.
Worked rule of thumb
Check each axle and axle group against its limit, not just total mass. If the steer axle is light and the drive axles are heavy, redistribute the load forward before moving.
Key points
- Mass, dimension, and restraint are separate legal regimes.
- Check every axle and axle group, not just total mass.
- Exceeding dimension limits requires permits and possibly escorts.
- Restraint is a force standard, not a strap count.
- Keep the centre of gravity low and centred.