5-Steps to Whole-Body Vibration (WBV) Risk Assessment Compliance

Introduction

Whole-body vibration (WBV) arises when mechanical oscillations are transmitted through a supporting surface (typically the seat or floor) into a worker’s body. Prolonged or excessive exposure to WBV can lead to health concerns, including aggravation and potentially a cause of lumbar spine disorders, vertebral disc degeneration, and chronic musculoskeletal pain.

In compliance with the Control of Vibration at Work Regulations 2005 (UK), a systematic and evidence-based WBV risk assessment process is required. This document outlines a detailed five-step procedure for identifying, quantifying, and mitigating WBV exposure in the workplace.

In the UK, enforcement is carried out by the Health and Safety Executive (HSE), who take the view that WBV exposure should be considered as part of your overall musculoskeletal injury management plan. Evidence is weak for a direct link between WBV and injury, so this approach ensures that common issues such as back-pain are investigated on the whole.

5-Steps to Compliance

This guide has been put together for you to aid in the process of complying with the regulations whilst taking a pragmatic approach to the risks involved as well as consideration for the approach of the HSE.

The steps below allow you consider all the factors involved to produce a risk assessment as required by the Control of Vibration at Work Regulations 2005.

Identification of At-Risk Workers

Determine Worker Exposure Profiles

Begin by compiling a comprehensive list of all personnel who operate, ride, or are regularly in contact with vehicles or platforms that may serve as sources of vibration. Whole-body vibration is normally defined as vibration that enters the body through the seat of people sitting down or the feet if you are standing. High-risk occupational roles commonly include:

• Earthmoving equipment operators (e.g., excavators, bulldozers, backhoe loaders)
• Roadwork and paving operators (e.g., vibratory rollers, compactors)
• Material handling drivers (e.g., forklifts, telehandlers, crane cabs)
• Agricultural machine operators (e.g., tractors, combine harvesters)
• Groundskeeping personnel (e.g., ride-on mowers, utility vehicles)
• Waste management workers (e.g., refuse collection trucks, dumpers)

Quantify Exposure Duration and Frequency

For each worker or task on your site, you need to establish the following information, which is vital to determine the exposure time for every individual. This may comprise a single operation or task or it may involve several smaller exposures, that need to be combined to find the daily exposure:

• Average daily usage duration (in minutes or hours)
• Task-specific frequency (i.e., continuous use, intermittent operation, etc.)
• Operating cycles (e.g., driving, idling, lifting, reversing)
• Shift structure, including number of breaks and rest periods

Use direct worker interviews, time-motion studies, machine usage logs, and telematics data (if available) to triangulate estimates of exposure time with high reliability.

Vibration Emission Data – How to Find it!

To quantify vibration magnitude (usually expressed as root mean square acceleration, RMS, in m/s²), select one of the two primary data acquisition methods:

Published Emission Data

Sources:

• Manufacturer Specifications: Some operators’ manuals include vibration emission values derived under standardized test conditions (e.g., ISO 2631-1). Whilst this is commonplace for hand arm vibration sources, WBV data is very limited in practice, which may render this approach almost useless.
• Regulatory Tools: Use guidance such as the HSE WBV Ready Reckoner, exposure tables, or industry-specific benchmarks for common machinery.
• Website Data: There are some websites developing data sources, which may be of value providing they have the specific machinery you are looking for.
• Peer Group Data: If you are part of a safety group or a large company with many departments or areas, there may be data available from other people who have conducted measurements themselves.

Note: Published data may underestimate real-world exposure due to idealized test conditions. Therefore, apply a safety factor (typically 1.2 to 1.5) when using these values in environments with adverse terrain or heavy wear.

The exposure ready reckoner below gives the points for a given vibration level and exposure time. Points can be simply added together to combine exposures and produce an overall daily exposure level as required by the Control of Vibration at Work Regulations 2005.

Exposure Ready Reckoner

Key

1. Read up the vibration magnitude scale on the left of the table
2. Then read across to the exposure time for an individual task
3. Take the number of points for that task
4. Repeat for tasks on the same day
5. Add together the points to produce daily exposure points and compare with table.

Conduct Direct Measurement

For greater reliability of data or if you cannot find the data another way, you can use field measurements using a tri-axial WBV accelerometer, compliant with ISO 2631-1:1997 and ISO 2631-5:2018 for low-frequency shock/vibration assessment.

Equipment:

The instrumentation setup will include a seat-pad accelerometer, in the form of a rubber disk, which has a triaxial accelerometer at its centre, a cable to connect the sensor to the measuring instrument and the unit itself, which will process the data to provide vibration magnitudes. It is vital that the instrument has the required filters and signal processing dedicated to Whole-body Vibration measurements

Best Practice:

Only competent technicians or Occupational Health and Safety or Hygiene professionals should undertake measurements as the factor that affect the results can be varied and must be understood.

Any measurement equipment must have the correct frequency filters to be able to measure WBV and ideally should be able to measure VDV as well. Any meter should have a valid calibration certificate.

The following elements of best practice should be included in your measurement methodology.

• Sampling duration: Ideally, you would measure for a full shift, but as this involves careful monitoring of the operator, it is not usually practical. Measurements of at least 30 minutes should be used so long as that includes all the variation in the task. This should result in an A_eq measurement, which is an equivalent energy average over the time of measurement.
• Axis of measurement: X (fore-aft), Y (lateral), Z (vertical). In the UK, the number used is the dominant axis, which simply means the largest of the 3 numbers. In other countries is can be the vector sum that is used.
• Sensor positioning: The seat-pad should be in direct contact with the vibrating surface and should remain still during the measurement. If on a soft surface, the operator moving around can affect the measurement, so some coaching may be required. You can use tape to keep the seat pad in place while you carry out the measurement.

Calculation of Daily Vibration Exposure – A(8)

The regulatory action and limit values are all based on an 8-hour ‘exposure’, which is a very important concept and requires the measured vibration level to be combined with the exposure time of the individual. The exposure is normalised to an 8-hour day so that all results can be compared to the same standard.

The daily exposure to WBV is normalized to an 8-hour reference period, expressed as A(8) (in m/s²), and calculated using the formula:

Where:

• a_w = RMS vibration magnitude or A_eq (m/s²)
• T = actual daily exposure time (in hours or minutes)
• T₀ = 8 hours (480 minutes)

Exposure Assessment Tools

You can use calculators provided by regulatory bodies such as the HSE WBV Exposure Calculator (Excel). There is also a database available at www.thecastlcloud.com. For each of these you will need to input:

• Measured or published RMS vibration value (m/s²)
• Daily exposure duration (minutes or hours)

Where workers may be exposed to more than one task or machine, then it is important to be able to combine the individual task exposures to produce an overall daily exposure. This is done using the root-sum-of-squares method, for which the formula is below:

Regulatory Thresholds

If A(8) indicates that an employee is likely to reach or exceed the EAV, implementation of a vibration control plan is mandatory. ELV breaches indicate significant regulatory non-compliance and require immediate remedial action. The ELV should not be exceeded.

Evaluation of Additional Risk Modifiers

Even if A(8) exposure is below legal limits, secondary environmental and ergonomic factors may elevate physiological risk. Don’t forget that the regulations are only a minimum standard, so any other risk elements must be considered.

Environmental Conditions

• Terrain roughness: Uneven surfaces (gravel, unpaved roads, construction sites) introduce high transient loads. A good example of this would be a forklift truck with hard tyres in a warehouse with gaps in the concrete flooring.
• Operational speeds: Excessive speed amplifies dynamic impacts, which may sound obvious, but do you have assessment methods in place and how are you going to control it?
• Weather: Wet or icy surfaces may increase jolting or sudden decelerations. Safe driving policies and enforcement could be the key in this area

Equipment Characteristics

• Machine age and condition: Degraded suspension or unbalanced wheels transmit more vibration, so maintenance regimes are very important to keep the vibration to a minimum
• Seat design: Non-suspension or poorly adjusted seats exacerbate vertical loading and will transmit more of the vibration. Training can be key to ensuring that operators use the correct seat settings.
• Tyre pressure and tread condition: Suboptimal tyre maintenance increases surface vibration. Ensure users are able to check tyre pressures and include daily walk-around checks to make sure equipment is safe and ready to use.

Human Factors

• Operator posture: Poor lumbar support or twisted spine alignment increases spinal strain. Include ergonomics in you staff training to help people manage their posure.
• Work duration: Extended shifts without adequate breaks intensify cumulative exposure
• Anthropometrics: Shorter or taller operators may not be adequately supported by standard seating systems. Are there options available for the seat type or adjustment.

Ergonomic factors, including posture assessments and seat adjustability audits, should be integrated into the WBV assessment protocol. In the UK this approach is the preferred method for the HSE, who like to see an overall assessment of musculoskeletal risks and injury, bringing WBV in as just one factor.

Empirical Assessment of Jolts and Shocks

It is possible to measure the added effect of shocks and jolts by using the Vibration Dose Value (VDV). This is usually only used by occupational health professionals or consultants although it can provide important information about the exposure of workers to this aggravating factor.

Vibration Dose Value (VDV)

Whole Body Vibration can be measured using VDV instead of RMS or Aeq. This is a fundamentally different way of creating an average from the vibration signal and uses a (fourth) root mean quad (RMQ). The reason for using this measure is that it weights the measurement more towards shocks and impulses, which are thought to be more damaging to the human body. The VDV is reported in m/s^1.75.

It is also important to understand that VDV is a cumulative value. The graph below shows the difference from an RMS value and the VDV as it accumulates over time. You can see the VDV kick upwards when there is a significant shock or ‘spike’ in the wave.

Once you have measured a VDV value you may need to adjust it if the measurement time and shift or exposure duration are different.

• Where:
  • VDV_(shift) = Vibration Dose Value over working shift
  • VDV_(measured) = measured Vibration Dose Value
  • Exposure Time = How long person is exposed to vibration
  • Measurement Time = Measurement time period
• Note:
  • Exposure Time and Measurement Time MUST be in the same units,
  • i.e. both in hour or minutes etc.

Documentation and Periodic Review of WBV Risk Assessment an Implement Control

A detailed risk assessment is vital to identifying and formally documenting the potential for injury in your workplace. This will highlight any at-risk workers showing their exposure levels compared to the regulations as well as any aggravating factors.

This should ALWAYS be followed by a detailed control and management plan, with actions and those responsible for carrying them out along with timescales and reporting routes

Report Components

• Equipment Inventory: List of all machines assessed, including make/model and vibration data
• Exposure Profiles: Duration and frequency for each worker or job function
• A(8) Calculations: Supporting data and exposure outcomes per machine and combined exposure totals
• Comparison to Legal Thresholds: EAV/ELV compliance status
• Health Surveillance Summary: Record of any reported symptoms (e.g., lumbar discomfort, fatigue, sciatica)
• Control Measures in Place: Engineering controls, administrative strategies, and PPE use
• Recommendations: Substitution, rotation, seating upgrade, speed control, operator training
• Action Plan: What specific actions are to be taken and who is responsible for them. This should include a deadline and management responsibility.

Update Triggers

Under the regulations, your risk assessment and controls should be updated regularly or in the event of any significant changes such as:

• Procurement of new machinery
• Changes in task assignments or shift lengths
• Operator complaints or reported symptoms
• Routine review cycles (typically annually)

Maintain the assessment as a live document, subject to review and revalidation. It should be accessible to health and safety auditors, insurers, and regulatory inspectors.

Castle Group Equipment You Can Use for This

VibA(8) Whole-Body Vibration System

Castle Group has been at the forefront of instrumentation for Hand Arm and Whole Body Vibration since the early 1990’s and has been continually developing the technology to produce standard compliant, yet simple to use instrumentation for industrial users.

The Castle VibA(8)

The VibA(8) is a state-of-the-art meter with intuitive operation and automatic sensor selection. Simply plug in the Whole-Body seat pad and the meter will select the correct settings for that device.

Designed for whole-body vibration measurements, this seat pad is ideal for assessing vibration exposure in vehicles and machinery.

Conclusion

Effective control of whole-body vibration exposure requires a multi-disciplinary approach involving technical measurement, ergonomic evaluation, operational review, and health monitoring. While A(8) provides a quantitative foundation, holistic risk management demands contextual understanding of site-specific conditions and human-machine interactions. A rigorous and well-documented WBV risk assessment will not only ensure legal compliance but also contribute to the long-term health and productivity of your workforce.