Vehicle Safety, Loading and Dimensions
Safety systems and pre-start checks
Before every trip, a driver must complete a pre-start check: tyres and pressures, brakes and air pressure build-up, lights and indicators, mirrors, couplings and safety chains, load restraints, and fluid levels. Know the purpose of systems like ABS, engine brakes and retarders, and exhaust brakes - they reduce brake fade on long descents but do not replace service brakes. Understand brake fade and how to manage it by selecting a low gear before a descent and using engine braking.
Loading and dimension limits
Loads must be secure and must not make the vehicle unstable. The load must not exceed the vehicle's GVM, axle group limits, or tyre ratings. Dimension limits for heavy vehicles: maximum width 2.5 metres (some vehicles 2.55 m), maximum height 4.3 metres, and maximum length varies by combination - a single rigid is generally 12.5 m, a semi-trailer combination 19 m, and B-doubles longer under permit or notice. Loads projecting beyond the vehicle need warning flags and, at night, lights. Overheight or overmass loads require permits.
Traps
Questions often confuse GVM with payload, or axle limits with total mass. Another trap is assuming a load is legal because it fits - it must also be within mass limits and properly restrained. Flags and lights on projections are commonly tested.
Rule of thumb
Check mass, then dimensions, then restraint. If any one fails, the load is not legal.
Worked example
A rigid truck with GVM 12 t and tare 5 t has a 7 t payload. Loading 8 t exceeds GVM even if the load fits within the tray.