Measurement adjustment is a nationally-agreed process that applies when a vehicle is being measured or weighed for compliance and enforcement purposes.
The Measurement adjustment recognises that a mass or dimension assessment outcome may potentially vary from time to time, due to:
- the weighing and measuring equipment used
- the inspection site characteristics
- measuring methods
- the conditions under which the measurements are made.
By applying an agreed adjustment to account for these possible variations, the measurement is based on the highest degree of accuracy achievable at any time and provides fairness to the outcome of the measurement process. This means the assessment can legally be relied upon in considering possible enforcement action.
Dimension measurement adjustment (DMA)
- Compliance bulletin 3 – Heavy vehicle dimension assessment (PDF, 142KB) - Provides information about the methods used to assess compliance with heavy vehicle dimension requirements and details the DMA used based on measurement method and vehicle length.
DMA relies on two key concepts:
- Measured dimension (MD) - the reading obtained from the measuring device.
- Assessed dimension (AD) - the measured dimension minus the relevant DMA.
MD - DMA = AD
The assessed dimension is compared with the dimension limit and breakpoints to determine the severity of any offence that may have occurred.
Mass measurement adjustment (MMA)
- Compliance bulletin 2 – Heavy vehicle mass assessment (PDF, 201KB) - Provides information about the methods used to assess compliance with mass requirements and details the MMA for each axle group based on the inspection site category.
MMA relies on two key concepts:
- Measured mass (MM) - the reading obtained from the weighing equipment
- Assessed mass (AM) - the measured mass minus the relevant MMA.
MM - MMA = AM
The assessed mass is compared with the mass limit and breakpoints to determine the severity of any offence that may have occurred.
Inspection site categories
Inspections sites used for weighing heavy vehicles are classified into three categories based on their physical characteristics; Category 1, 2 or 3.
- Inspection sites that include a weighbridge facility will generally meet the physical characteristics required to be classified as a Category 1 site.
- Purpose built roadside inspection sites will generally meet the physical characteristics required to be classified as a Category 1 or 2 site.
- Mobile intercept sites generally meet the physical characteristics required to be classified as a Category 3 site.
Oversize overmass (OSOM) heavy vehicle mass assessment
The MMA is calculated differently for OSOM vehicles.
- Compliance bulletin 8 – OSOM heavy vehicle mass assessment (PDF, 161KB) - Provides information about methods used to assess compliance with OSOM heavy vehicle mass requirements.