What happens to TMH 9 ratings: from visual rating to project shortlist

In South Africa, a TMH 9 rating, the record of distress type, degree and extent for one road segment, is submitted in a TMH 18 road-data file, turned into a named condition index, confirmed by a panel inspection and, for a candidate road, handed to a TRH 12 project investigation for pavement rehabilitation. TMH (Technical Methods for Highways) and TRH (Technical Recommendations for Highways) are South African road-manual series, and TMH 9 is the road manual for the visual assessment of pavements (Committee Draft Final, May 2016).

Key facts

• TMH 9, the South African visual assessment manual for road pavements (Committee Draft Final, May 2016), records distress type, degree and extent per segment and gives no index formula.
• A TMH 18 road-data visual condition file, .vcf in Draft Version 4 and .flx in Committee Draft 5.0, carries index columns but no field that names the index method.
• A condition index from TMH 9 ratings should name its variant: TRH 22 section 6.2.2, TRH 22 Addendum A.3, TMH 22 Appendix J-6 or TMH 22 Appendix J-5 (deduct-point).
• TMH 22 section G.10 describes a panel inspection as the first step in confirming network-level results, and one objective is to set the exact limits of proposed projects.
• TRH 12 (Draft, 1997) sections 1.3.2 and 1.3.3 separate network-level identification of roads from a more detailed project-level study that identifies specific needs for rehabilitation design.
• A network average is not a project decision: network screening identifies candidates and a project investigation answers design questions.

What is a TMH 9 rating, and what does it leave undecided?

A TMH 9 rating is an assessor's record of each visible distress on a pavement segment by its type, its degree (how severe it is) and its extent (how widespread it is over the segment). Part A sets out these attributes in section A.2 and lists standard segment lengths in Table A.3 (COTO, 2016b); the survey itself is covered in how to run a TMH 9 visual assessment.

TMH 9 stops at the rating. Part A names visual condition indices and maintenance and rehabilitation needs as outputs of processing the data, and calls Parts A to E companions to TMH 22 (Road Asset Management Manual, Draft, March 2013) in sections A.1.1 and A.1.3. No part of TMH 9 gives an index formula, and finding uniform sections of distress is not the purpose of the assessment (section A.3) (COTO, 2016b).

What stages sit between a TMH 9 rating and a project investigation?

Five stages carry a rating to a project, and the manual or manual part changes at each hand-off.

Narrated film · 1:28

From TMH 9 rating to project shortlist

A five-stage rail follows one rating from the TMH 9 sheet to a TRH 12 investigation, with a hand-off marker where the manual changes.

Read the film transcript

What happens to a TMH 9 rating once the assessor hands it in? TMH 9, the South African manual for visual assessment of road pavements, records each distress by type, degree and extent, and gives no index formula. Five stages carry that rating to a project, and the manual, or the part of it, changes at each hand-off. Next, the ratings go into a TMH 18 road-data file, Draft Version 4 or Committee Draft five point zero. Then TRH 22 or TMH 22, the pavement and asset management manuals, describe the index methods. Needs determination flags segments, and a panel inspection confirms each candidate and sets its limits. A rehabilitation candidate goes on to a TRH 12 project investigation, the nineteen ninety-seven draft on flexible pavement rehabilitation. Name the index variant every time, because neither version of the TMH 18 file says which method produced it. In this synthetic example, the nine index values average fifty-nine point two, pointing to no particular kilometre. The authority's rule flags segments four and five, which stand well below the other seven. The panel inspection then sets the project limits from five point six to ten point four kilometres. A TRH 12 investigation divides the whole four point eight kilometres into three uniform lengths. Screening names the candidates, but a network average is not a project decision. Next, see TMH 13 on automated measurement, and the South African Pavement Engineering Manual on investigations.

Stage	Governing document and clause	Edition and status
1. Rating	TMH 9 Part A, sections A.2 to A.5; Part B for flexible pavements	Committee Draft Final, May 2016
2. Visual condition file	TMH 18, section 5.2	Draft Version 4, October 2014; Committee Draft 5.0, February 2016
3. Index	TRH 22 (Pavement Management Systems), section 6.2.2; or TMH 22 Part E with Appendices J-5 and J-6	Draft, 1994; Draft, March 2013
4. Needs and panel inspection	TMH 22 Parts F and G, including G.10; or TRH 22, chapters 7 and 8	Draft, March 2013; Draft, 1994
5. Project investigation	TRH 12, sections 1.3.2 and 1.3.3	Draft, 1997

Network screening identifies candidates; project investigation answers design questions, a line TRH 12 draws (Department of Transport, 1997).

What does a TMH 18 file add to TMH 9 ratings?

A TMH 18 (Road Asset Data Electronic Exchange Formats) submission file places the ratings in a fixed layout and adds index columns. In Draft Version 4 (October 2014) the flexible-pavement visual summary is a .vcf file and in Committee Draft 5.0 (February 2016) a .flx file, both semicolon-delimited (section 1.1). Section 5.2 of each lists the road, lane, start and end kilometres, date, a degree and an extent for each distress, and seven index columns, the first being the visual condition index (VCI). Each points to TMH 9 Part B for the detailed visual condition specification (COTO, 2014) (COTO, 2016i).

Neither version has a field that names the method behind the index values, so a well-formed file can carry an index nobody can trace (COTO, 2014) (COTO, 2016i). A lane code says which lane a row describes, whereas TMH 9 says a multi-lane assessment concentrates on the worst lane (section A.5.1) (COTO, 2016b). Verify the ratings before storing them: TMH 22 section D.5.11 and Appendix J-4 give an example routine that flags conflicting ratings (COTO, 2013).

Which condition index do TMH 9 ratings become under TRH 22 or TMH 22?

TMH 9 supplies no formula, so the index depends on the method chosen. The manuals describe three routes:

• TRH 22 (Draft, 1994), section 6.2.2, proposes a VCI formula built from degree and extent ratings and a weight for each distress; its Technical Addendum A.3 describes a modified method, among proposals the addendum calls not yet accepted current practice (CSRA, 1994).
• TMH 22 (Draft, March 2013), section E.2.1, describes a VCI for flexible paved roads, calculated by the method of Appendix J-6 as an arithmetic aggregation of TMH 9 ratings (COTO, 2013).
• TMH 22 also describes deduct-point indices under Appendix J-5, such as the condition index for surfacing (CISURF) and for flexible pavement structure (CIPAVE, also printed CIFPAVE) (COTO, 2013).

The TRH 22 and TMH 22 variants differ in form, constants or weight set, so compare a condition index only with one from the same variant. TMH 22 neither cites TRH 22 nor says that it replaces it; treat TMH 22 as the successor in practice and name both by edition (COTO, 2013). How to turn TMH 9 ratings into a visual condition index owns the arithmetic.

How does needs determination turn a condition index into a candidate list?

Needs determination flags segments, then joins the flagged segments into potential projects. TRH 22 section 7.2 lists four ways to flag a segment: an index below a limit, ratings above a limit, an assessor's recommendation and instrument results. Section 7.3 joins flagged segments into potential projects, because treatment is usually applied to several segments or parts of segments (CSRA, 1994). TMH 22 section G.4 describes technical needs determination: treatments are mostly triggered at intervention levels, by selection rules that usually represent the authority's own practice (COTO, 2013).

A flag is not yet a project. TMH 22 section G.10 and TRH 22 chapter 8 note that some network-level data, such as visual assessments, are aggregated per segment, so results are confirmed by further investigation, beginning with a panel inspection (COTO, 2013) (CSRA, 1994). The panel confirms the state of the asset and its urgency and determines the exact limits of the proposed project; its essential information includes the TMH 9 ratings, preferably on the assessment forms, with the indices (section G.10.2). Routine and periodic maintenance may be confirmed by the panel alone; rehabilitation needs further investigation before a final decision (COTO, 2013).

TRH 22 section 6.2.4 defines a network condition number, an average index weighted by condition and segment length, for comparing sub-networks and tracking change over time (CSRA, 1994). A network average is not a project decision.

What does a TRH 12 project investigation add to TMH 9 ratings?

A TRH 12 project investigation adds what network data lack: more detailed tests, the causes of distress and a division of the road into lengths needing different measures. TRH 12 (Flexible Pavement Rehabilitation Investigation and Design, Draft, 1997) is not Draft TMH 12 (2000), an unsealed-road rating manual that TMH 9 Part E has since withdrawn (COTO, 2016k). Section 1.3.2 says a network-level study, working from the average expected condition of pavements, identifies pavements that may need rehabilitation; after an economic evaluation, a more detailed project-level study identifies specific needs. Section 1.3.3 says more detailed tests can be warranted because a wrong rehabilitation decision could be costly, and lists contributing factors such as traffic loading, drainage problems and expansive subgrades, which a rating does not diagnose (Department of Transport, 1997).

Section 1.4.1 does not take the identified length as uniform: some sections may be distressed locally, some only in the surfacing and some may be sound, and the aim is to divide the length into distinct lengths needing different measures; the initial assessment covers the whole length first (section 1.4.2) (Department of Transport, 1997). A TMH 9 segment is not that division (see segments, uniform sections and reporting intervals).

What does the sequence look like on one synthetic road?

Synthetic example. Every value below is invented. Road S1 is a rural flexible road of 18.0 km, rated as nine segments of 2.0 km. The ratings go into a TMH 18 Draft Version 4 .vcf file, and the submission note names the index as the TMH 22 Appendix J-6 VCI.

The nine index values, in segment order, are 66, 64, 62, 42, 40, 65, 67, 63 and 64 (dimensionless). Their mean is 533 / 9 = 59.2, which points to no particular kilometre. Segments 4 and 5, km 6.0 to 10.0, stand well below the rest, so the authority's own rule flags both as one candidate of 4.0 km. The panel inspection finds the distress running from km 5.6 to km 10.4 and sets those project limits: 10.4 minus 5.6 is 4.8 km.

A TRH 12 initial assessment then covers all 4.8 km and divides it into three uniform lengths: km 5.6 to 7.4, 7.4 to 9.2 and 9.2 to 10.4, or 1.8 + 1.8 + 1.2 = 4.8 km. The 2.0 km ratings could not have produced those boundaries.

What are the steps from rating to investigation, and what should you keep?

1. Hand in the rated segments with their identifiers. Return road, lane, start and end kilometres, assessor, date and TMH 9 edition with every segment. Keep: the completed forms.
2. Verify the ratings before they are stored. Run the authority's routine for conflicting ratings. Keep: the flagged segments and their resolution.
3. Package the ratings in a TMH 18 visual condition file. Name the version, and keep every row inside its road's start and end kilometres (values outside are discarded, section 5). Keep: the file as submitted.
4. Name the index variant before calculating. State which TRH 22 or TMH 22 method produced the index, since the file cannot say. Keep: the unchanged ratings beside the named index.
5. Determine network needs from the index and the ratings. Apply the authority's trigger rules and combine neighbouring flagged segments into candidate projects. Keep: the rule used and the candidate limits.
6. Confirm each candidate by panel inspection. Record the decision, limits, urgency and reasons (TMH 22 section G.10.4). Keep: the panel record.
7. Open a TRH 12 investigation for each confirmed rehabilitation candidate. Treat network values as inputs and divide the whole length into uniform lengths. Keep: a hand-off note naming the manual editions used.

What do the manuals leave undecided, and what is commonly misread?

What the manuals do not decide

TMH 9 does not define an index or choose a treatment (COTO, 2016b), and TMH 18 does not name the index method (COTO, 2014) (COTO, 2016i). TMH 22 leaves project-level work outside its scope (sections D.3.1 and G.9.1) and TRH 22 determines needs at network level; both give example trigger rules (TRH 22 section 7.4, TMH 22 Appendix J-8), but the limits for a road are the authority's own (CSRA, 1994) (COTO, 2013). TRH 12 prescribes no rigid procedure: it describes accepted practice and refers to design methods without detailing them (sections 1.2 and 1.4.1) (Department of Transport, 1997).

Common misreadings

• "TMH 22 replaced TRH 22." TMH 22 does not say so, and both are drafts; cite each by edition.
• "A good network average clears a road." It does not; a rehabilitation decision needs a project-level investigation such as TRH 12 describes.

Which manual governs each stage

Stages of the journey, the manual that governs each one, and the evidence each stage should leave behind.

Stage	Governing manual	Evidence this stage produces
1. Rating sheet	TMH 9	Completed assessment forms with road, lane, start and end kilometres, assessor, date and TMH 9 edition, and the type, degree and extent of each distress.
2. Visual condition file	TMH 18	The file as submitted, with its TMH 18 version (.vcf in Draft Version 4, .flx in Committee Draft 5.0), the verification log and a note of the lane each row describes.
3. Index by a named variant (TRH 22 section 6.2 or TMH 22 Part E)	TRH 22	The index value per segment with its variant named, TRH 22 section 6.2.2 or TMH 22 Appendix J-5 or J-6, and the unchanged ratings beside it.
4. Needs and panel inspection	TMH 22	The needs rule used, the flagged segments, the candidate project limits and the panel record of decision, urgency and reasons (TMH 22 section G.10.4).
5. Project investigation	TRH 12	A hand-off note naming the manual editions, then the investigation's own record of tests, uniform lengths and rehabilitation options (TRH 12 sections 1.3.3 and 1.4).

The journey, step by step

1. Hand in the rated segments with their identifiers

   Return road, lane, start and end kilometres, assessor, date and TMH 9 edition with every segment, because every later stage joins on those fields. Keep: the completed forms.

2. Verify the ratings before they are stored

   Run the authority's routine for conflicting ratings; TMH 22 section D.5.11 and Appendix J-4 give an example. Keep: the flagged segments and their resolution.

3. Package the ratings in a TMH 18 visual condition file

   Name the version, Draft Version 4 (.vcf) or Committee Draft 5.0 (.flx), and keep every row inside its road's start and end kilometres, because values outside are discarded. Keep: the file as submitted.

4. Name the index variant before calculating

   State which TRH 22 or TMH 22 method produced the index (TRH 22 section 6.2.2, TRH 22 Addendum A.3, TMH 22 Appendix J-6 or J-5), because the file cannot say. Keep: the unchanged ratings beside the named index.

5. Determine network needs from the index and the ratings

   Apply the authority's trigger rules and combine neighbouring flagged segments into candidate projects (TRH 22 sections 7.2 and 7.3; TMH 22 section G.4). Keep: the rule used and the candidate limits.

6. Confirm each candidate by panel inspection

   Take the TMH 9 forms, the indices and the traffic data to the panel and record the decision, limits, urgency and reasons (TMH 22 section G.10). Keep: the panel record.

7. Open a TRH 12 investigation for each confirmed rehabilitation candidate

   Treat network values as inputs, assess the whole length first and divide it into uniform lengths (TRH 12 sections 1.3.3 and 1.4). Keep: a hand-off note naming the manual editions used.

Frequently asked

What happens to TMH 9 ratings after the assessment?

TMH 9, the South African road manual for visual assessment of pavements, supplies ratings of distress type, degree and extent. They are submitted in a TMH 18 road-data file, turned into a named visual condition index, used in a network needs determination, confirmed by a panel inspection and, for a candidate road, passed to a TRH 12 (flexible pavement rehabilitation) project investigation. Each stage draws on a different manual or part, and each should keep the unchanged ratings.

Does a TMH 18 file say which visual condition index it holds?

No. In both Draft Version 4 and Committee Draft 5.0 of TMH 18, the South African road-data exchange manual, the flexible-pavement visual condition file in section 5.2 has columns for index values but no field that names the calculation method. State the variant, for example the TMH 22 Appendix J-6 visual condition index, in the submission note and keep the ratings unchanged beside the index.

Is a network average enough to choose a rehabilitation project?

No. A network-level system works from the average expected condition of pavements. TRH 12, the South African flexible pavement rehabilitation manual, says in section 1.3.2 that a more detailed project-level study identifies specific needs and supports rehabilitation design, and in section 1.3.3 that more detailed tests can be warranted. Network screening identifies candidate roads; a project investigation answers design questions such as the cause of distress and where uniform lengths begin.

Does TMH 22 replace TRH 22?

No replacement is stated. TMH 22 (Draft, March 2013), the South African road asset management manual, covers more ground and is the successor in practice to TRH 22 (Draft, 1994), the pavement management manual, but it neither cites TRH 22 nor states that it replaces TRH 22. Both are drafts with their own index methods, so cite the edition used and name the index variant rather than assuming that one continues the other.

What is a panel inspection in TMH 22?

TMH 22, the South African road asset management manual, describes a panel inspection in section G.10 as the first step of further investigation after a network-level needs determination. A panel of regional, asset management, materials and structures staff confirms the state of the asset reported by the condition data, confirms its urgency and determines the limits of proposed projects. Rehabilitation projects still need further investigation afterwards.

Is TRH 12 the same as TMH 12?

No. TRH 12 (Draft, 1997) is the South African manual on flexible pavement rehabilitation investigation and design, published by the Department of Transport for the Committee of Land Transport Officials. Draft TMH 12 (2000) is a different document in a different series: a visual assessment manual for unsealed roads, since withdrawn by TMH 9 Part E. Name the series, the number and the subject whenever either is cited, because the two numbers are often confused.

Where this connects

Under TRH 12 section 1.4.2, the initial assessment decides on tests such as deflection and profile measurements (Department of Transport, 1997); TMH 13 (Automated Road Condition Assessments, Committee Draft Final, May 2016) describes such measurement by automated devices, typically for network use. The investigation continues in SAPEM (South African Pavement Engineering Manual) Chapter 6, Road Prism and Pavement Investigations (Second Edition, October 2014).

Last reviewed on 21 October 2026 against the editions listed in the stages table.

References

1. COTO (2016b). TMH9: Manual for Visual Assessment of Road Pavements. Part A: General. Committee Draft Final, May 2016. Original source.Section A.2: degree and extent
2. COTO (2016k). TMH 9: Manual for Visual Assessment of Road Pavements. Part E: Unpaved Roads. Committee Draft Final, May 2016. Original source.Sections, tables and clauses are cited inline in each guide
3. COTO (2014). TMH 18: Road Asset Data Electronic Exchange Formats. Draft Version 4, October 2014. Original source.Sections, tables and clauses are cited inline in each guide
4. COTO (2016i). TMH 18: Road Asset Data Electronic Exchange Formats. Committee Draft 5.0, February 2016. Original source.Sections, tables and clauses are cited inline in each guide
5. CSRA (1994). Draft TRH22: Pavement Management Systems. Pretoria: Department of Transport, 1994. Original source.Technical Addendum A.3, equations A.3.1–A.3.3 and Table A.3.1, printed pp. 125–126; Section 6.2.2, printed pp. 55–56, for alternative-weight normalisation
6. COTO (2013). Draft TMH 22: Road Asset Management Manual. Draft, March 2013. Original source.Sections, tables and clauses are cited inline in each guide
7. Department of Transport (1997). TRH12: Flexible Pavement Rehabilitation Investigation and Design. Draft TRH12, Pretoria: Department of Transport for COLTO. Original source.Chapter 1: rehabilitation design process; investigation, evaluation, analysis and economic appraisal

Use the manual edition and project requirements that apply to your work. Worked examples use synthetic values and are not site-specific design advice.