TMH 9 is the South African Manual for Visual Assessment of Road Pavements, published by the Committee of Transport Officials (COTO). It standardises which defects are recorded on a road segment and how each one is rated, across Parts A (general), B (flexible), D (block) and E (unpaved).

TMH 9 visual assessment explained — RoadSense

Table 1. The TMH 9 parts and the pavement family each covers
Part	Covers	Assessment form
Part A	General — method, definitions, the degree and extent scales	Applies to all parts
Part B	Flexible (bituminous-surfaced) pavements	Surfacing, structural and functional rows
Part D	Block (segmental concrete) pavements	Block-specific defect rows
Part E	Unpaved (gravel) roads	Gravel defect and functional rows

The 2016 committee draft final is the version in general use. TMH 9 supplies the ratings only — it publishes no condition-index formula. Indices such as the Visual Condition Index (VCI) are computed from TMH 9 ratings by the deduct methods published in TMH 22 and, for unpaved and block roads, the ReCAP (2020) Raters' Guidelines.

Table 2. Degree and extent scales, TMH 9 Part A Tables A.1 and A.2
Value	Degree (severity)	Extent (how widespread — the percentage is a guide only)
0	No distress visible	Not rated — the defect does not occur
1	Slight; first signs only	Isolated, not representative of the segment (< 5%)
2	Slight to warning	Over parts of the segment; more than isolated (5–10%)
3	Warning; secondary defects start	Intermittent over most of the segment, or extensive over a limited portion (10–25%)
4	Warning to severe	More frequent over a major portion (25–50%)
5	Severe; secondary defects well developed	Extensive over the entire segment (> 50%)

Figure 1. The TMH 9 degree × extent rating grid. Degree runs up the vertical axis and extent across the horizontal, so every defect on a segment resolves to one of 25 rated cells. Separating severity from spread is the core of the method: a badly cracked 20 m patch (high degree, low extent) is a localised repair, while hairline cracking over the whole kilometre (low degree, high extent) is a network-level surfacing decision. Deduct methods read this cell, not a single combined score.

Functional items are rated by degree only

Not every row on a TMH 9 form carries an extent. Functional items — riding quality (roughness), skid resistance, surface drainage, shoulders, and for unpaved roads drainage on and off the road — are rated by degree alone, 1 = very good to 5 = very poor (TMH 9 Part B Tables B.22–B.24; Part E Tables E.18–E.19). Deduct methods either read these from degree-only tables or assign them a fixed extent.

Worked example — rating one flexible segment

Block cracking is visible as a well-developed pattern with secondary spalling over roughly the whole segment: degree 5, extent 5.
A single pothole cluster near one culvert: degree 3, extent 1 — severe enough to matter, but isolated.
No rutting is visible at all: degree 0, and the row contributes no deduct.
Riding quality is rated degree 4 — functional, so no extent is recorded.

Same segment, two very different findings: the cracking is a full-length surfacing intervention, the potholes a localised patch. TMH 9 keeps them separable because degree and extent are recorded independently.

How RoadSense captures TMH 9 assessments

RoadSense captures TMH 9 visual assessments in the VisualAssessor apps against the COTO assessment forms for flexible, block and unpaved roads, with more than 30 distress types per form. Each rating is recorded with its degree and extent, is tied to the exact georeferenced video frame the assessor was looking at, and moves through a Draft → Submitted → Approved lifecycle. Unrated rows stay unrated — a blank row is never silently written as degree 0 — and the stored ratings feed the condition indices and the TMH 18 exports without re-keying.

What is TMH 9?

TMH 9 is the South African Manual for Visual Assessment of Road Pavements, published by the Committee of Transport Officials (COTO). It standardises how a road segment is walked or driven, which defects are recorded, and how each defect is rated, so that assessments by different raters on different networks are comparable.

What is the difference between degree and extent in TMH 9?

Degree describes how severe a defect is at the places where it occurs, on a 1–5 scale from slight first signs to severe with well-developed secondary defects. Extent describes how much of the segment is affected, on a 1–5 scale from isolated (under about 5% of the length) to extensive over the entire segment (over about 50%). The two are rated independently for the same defect.

Does TMH 9 define the Visual Condition Index?

No. TMH 9 defines the ratings only. The VCI and related indices are computed from those ratings by deduct methods published elsewhere — TMH 22 Appendix J-5 (the Deduct Point System, giving CISURF and CIPAVE for flexible pavements), TMH 22 Appendix J-6 (the weighted-deduct VCI for flexible pavements), and the ReCAP (2020) Raters' Guidelines Tables E.7-1 and D.5-1 for unpaved and block pavements.

References

Committee of Transport Officials (COTO) (2016) TMH 9: Manual for Visual Assessment of Road Pavements, Parts A (General), B (Flexible pavements), D (Block pavements), E (Unpaved roads). Committee Draft Final. Pretoria: Department of Transport.
Committee of Transport Officials (COTO) (2013) TMH 22: Road Asset Management Manual, Appendices J-5 and J-6. Draft V8b. Pretoria: Department of Transport.
Van Zyl, G. and Van der Gryp, A. (2013) 'Development of a deduct point system for the visual assessment of flexible pavements', Proceedings of the 32nd Southern African Transport Conference, pp. 383–393.
Pinard, M.I. and Geddes, R. (2020) Raters' Guidelines for the Visual Assessment of Road Pavements, Parts B, D and E. ReCAP/DFID.

For the full set of survey standards RoadSense reports against, see the standards hub, or contact us to discuss a visual condition assessment of your network.

TMH 9: Visual Assessment of Road Pavements (degree & extent)