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Multiple impairment ratings
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Combined values chart and WPI in NSW CTP claims

Many injured people have more than one impairment after a serious motor accident. The question is usually not “add the numbers together”, but whether the applicable method requires values to be combined.

Quick answer

In NSW CTP, separate impairment percentages are generally combined using the AMA4 Combined Values Chart unless the relevant method says otherwise. The report should explain which values were combined, which were not allowed to combine, and why.

Separate CTP impairment evidence folders arranged around a central assessment file for combined values review.
Separate impairment percentages are usually combined, not simply added.

What this means in a NSW CTP claim

Combining is different from adding

The combined values approach prevents impairment percentages from exceeding the whole person or region. Two separate numbers may produce a lower final percentage than simple arithmetic addition.

The method decides what can combine

Some body-system methods allow combination; others require a single best method or prohibit combining overlapping impairments. A report should explain the rule, not just show a final number.

Only comparable values should be combined

Regional impairments may need conversion to WPI before being combined with other WPI values. Combining values at the wrong level can distort the result.

Physical and psychological ratings have a special threshold rule

When deciding whether impairment is greater than 10% in NSW CTP, physical injury ratings cannot be combined with psychiatric or psychological ratings.

Where combined values mistakes appear

Errors often appear before the chart is even used. One value may still be a regional impairment rather than WPI, one injury may duplicate another method, or a psychological percentage may be mixed into a physical threshold calculation. Another common problem is a report that gives the final combined percentage without showing the source values and order of combination. For review purposes, the useful audit is simple: identify each separate rating, confirm it is allowed to stand on its own, convert it correctly, then check whether the Guidelines allow it to be combined for the question being decided.

Evidence that usually matters

Separate injuries
Each impairment must be identified and rated by the correct method before any combination step.
Conversion
Upper extremity, lower extremity or other regional ratings may need conversion to WPI first.
Combination rule
The report should identify whether values are combined, added, excluded or assessed by one dominant method.
Threshold use
Check whether the final number is being used for damages eligibility or another entitlement issue.

Common traps

  • - Do not add numbers unless the method expressly says to add.
  • - Do not combine overlapping impairment methods.
  • - Do not combine physical and psychological impairment to pass the 10% threshold.
  • - Do not rely on a final combined number without seeing the source values.

Practical next steps

  1. 1. List each rated impairment separately.
  2. 2. Check whether each value is already WPI or still regional impairment.
  3. 3. Trace the combined values step in the report.
  4. 4. Ask why any impairment was excluded from combination.
  5. 5. If the report skips the method, get the calculation checked.

Frequently asked questions

Why is my combined WPI lower than the added numbers?

That is often how the Combined Values Chart works. It combines impairment against the remaining whole person rather than simply adding percentages.

Can every injury be combined?

No. The applicable body-system method may prohibit combination or require one method to be selected.

Can physical and psychological WPI be combined for the 10% threshold?

No. NSW CTP rules state that physical and psychiatric or psychological impairment ratings cannot be combined for that threshold question.