What Makes a Defensible Pendulum Report

Accreditation as the foundation

UKAS ISO/IEC 17025 accreditation is the single most important defensive feature of a pendulum report. A non-accredited report can be challenged on technical-competence grounds before its substantive findings are even discussed; an accredited report carries the implicit verification of the lab's methodology, calibration, traceability and quality system.

Detail in our UKAS accreditation guide.

Mandatory report content

A defensible pendulum report contains, as a minimum:

• Identification of the testing organisation and its UKAS schedule reference
• Identification of the property tested and the date of testing
• Identification of who instructed the testing and on what basis
• The standard followed (BS EN 16165:2021 Annex C, or BS 7976-2 historical)
• The instrument used (model, serial number, calibration validity)
• The slider used (Slider 96, 55 or 57)
• The calibration sequence followed on the test day
• The slider conditioning protocol used between test sets
• For each test location: the location description (with reference to a plan or photograph), the contamination conditions (wet/dry/specific), the individual swing readings per direction, the calculated mean PTV
• Photographic record of each test location
• Surface roughness (Rz) data where included
• Discussion and findings written in unbiased language
• The technical signatory's name, position and signature
• Any limitations or caveats explicitly identified

Photographs are evidence

Each test location should be photographed before testing — capturing the surface as found, the lighting, any contamination present, and the surrounding scene. These photographs are evidence in their own right and are routinely scrutinised by opposing experts in litigation. A report without location photographs is weaker, not just less attractive.

Methodology disclosure

The report should make explicit:

• Which standard the methodology follows (and any deviations)
• How test locations were selected (representative sample, specific incident location, full-zone coverage)
• Whether testing was carried out post-clean, mid-cycle, end-of-day
• Whether any preparation was done to the surface and why
• The footwear/slider assumption and any rationale

Methodology disclosure pre-empts cross-examination on these points.

Raw data, not just conclusions

Reports that quote only an overall pass/fail or a single rounded PTV per area are evidentially weak. Defensible reports include the raw swing readings — every individual swing, in every direction, at every location, wet and dry — so that the next reviewer can verify the calculation and assess scatter within each test set. Compliant UKAS reporting includes raw data as a matter of course.

Unbiased language

The report's prose should describe, not advocate. 'The surface achieved a wet PTV of 28 at this location, placing it in the moderate slip-potential band per HSE guidance' is defensible. 'The surface is dangerous and unfit for use' is advocacy and undermines the report's standing under CPR Part 35. Where conclusions need to be drawn, they should be in the conclusions section, separated from the data, and qualified as the expert's opinion.

Limitations, explicitly

Defensible reports state their limitations:

• Locations not tested and why (access, programme, scope)
• Contamination conditions not assessed (oil-only environments tested wet, etc.)
• Time elapsed since the incident (in post-incident testing)
• Any equipment or methodology departures from standard practice
• The expert's own areas of expertise relative to the matter at hand

An expert who acknowledges limitations is more credible than one who claims complete knowledge of every aspect.

CPR Part 35 compliance, where relevant

For reports likely to be used in litigation, full CPR Part 35 compliance should be built in from the outset — overriding duty statement, expert qualifications, statement of instructions, statement of truth. Adding these later is harder than including them from the first draft.

The single defensive principle

A defensible pendulum report is one that anticipates the questions the opposing expert will ask, and answers them in the document itself. Methodology, calibration, conditioning, location selection, photographic record, raw data, and limitations — all stated explicitly. When the opposing expert reviews the report and finds nothing they can attack on technical grounds, they have to attack the substantive findings on their merits — and that is where good methodology and accurate data win.