Vibration exposure · GB · Three-axis A(8)
Combine whole-body vibration readings by axis
Calculate daily x, y and z exposure from frequency-weighted RMS readings and find the highest daily axis.
By HSECalc · Published
Check that this method fits your task
Enter x/y Wd-weighted and z Wk-weighted RMS readings BEFORE the axis multiplying factors. This tool applies 1.4 to x/y and 1 to z. Not a vibration-dose-value or shock/jolt assessment.
Choose your inputs and work through the steps
- Obtain frequency-weighted RMS x, y and z readings: Wd for x/y and Wk for z. This worksheet expects values before axis multiplying factors.
- Record each task’s duration and corresponding axis values. Do not substitute a previously calculated A(8), VDV or an unweighted reading.
- Combine periods within each axis, apply 1.4 for x/y and 1 for z, then use the highest daily axis. Do not add the three final axis results.
For each axis: k × √[Σ(a² × hours) ÷ 8], with kx=ky=1.4 and kz=1. Compare the largest axis A(8). GB EAV 0.5 and ELV 1.15 m/s² A(8).
A worked example
Illustrative values explain the tool; they are not prescribed inputs for your work.
- For four hours, the duration factor is √(4 ÷ 8).
- Daily x = 1.4 × 0.4 × √0.5 = 0.396; y = 0.198; z = 0.424 m/s².
- The highest daily axis is z, 0.424 m/s²; retain precision when comparing thresholds.
Read the result and decide what needs checking
GB daily A(8) action and limit values are 0.5 and 1.15 m/s². Review exposure controls at the action value and ensure the limit is not exceeded.
Shocks and jolts can need additional assessment. A favourable RMS A(8) result is not a complete evaluation of a vehicle task or its ergonomics.
Common questions
Do I add the three axes together?
No. Daily exposure is calculated separately for each axis; this tool reports the highest.
What if the instrument already applied 1.4?
Do not enter that value here. Obtain the correctly frequency-weighted RMS readings before multiplying factors.
Can A(8) assess shocks and jolts fully?
No. They can require additional assessment, including an appropriate VDV method.
References and scope notes
Use the current official guidance and the instructions for your actual equipment. HSECalc is independent; a reference is not an endorsement. Read how we use methods and sources or report a correction.