TMH 18 Combined Instrument Data (CID) — RoadSense

A CID export is a per-chainage combined dataset: every interval along a surveyed road is described by a row of instrument readings tied to a physical location. Engineers and asset managers rely on this combined format so that condition data from different profiler vendors and survey runs can be compared, merged, and audited on a common chainage reference — rather than as disconnected per-instrument logs.

Table 1. Measurement families carried in a CID record
Field family	Example content	Source instrument
Location referencing	Road ID, chainage from/to, GPS lat/long	GNSS + linear referencing
Roughness	IRI per segment, m/km	Inertial profilometer
Rut depth	Millimetres, per wheelpath	Laser profilometer
Macrotexture	MPD, mm	Laser profilometer
Survey metadata	Date, direction, lane, operator	Survey record

Figure 1. Instrument and positioning streams are combined per chainage interval into a TMH 18 §19 CID record ahead of COTO submission.

IRI_segment = 1/n · Σ_i=1ⁿ IRI_i

where n = number of raw reporting intervals (typically 10 m) inside the CID reporting segment (typically 100 m); the same aggregation applies to rut depth and MPD.

Worked example — building one 100 m CID row

1. Ten 10 m IRI values for chainage 12+400–12+500: 3.2, 3.4, 3.1, 3.8, 3.6, 3.3, 3.5, 3.9, 3.4, 3.8.

2. Sum = 35.0 → segment IRI = 35.0 / 10 = 3.50 m/km.

3. The same segment's rut = 6.4 mm, MPD = 0.82 mm.

4. Row written as chainage 12+400–12+500 with GPS from/to.

CID row: 12+400–12+500 · IRI 3.50 m/km (Good) · rut 6.4 mm (Sound) · MPD 0.82 mm — one line of a network-level submission.

Interactive: ten raw 10 m IRI readings across chainage 12+400 to 12+500 collapse into a single 100 m CID row whose IRI, rut and MPD are the arithmetic mean of their sub-intervals (§19). Adjust road roughness and reading variability, or drag a bar up to spike a pothole, and watch the mean line slide and the TRH 12 condition chip flip between Good (<4.0), Fair (4.0–6.0) and Poor (>6.0 m/km) — showing how averaging over 100 m dilutes isolated rough intervals yet a run of them still moves the band.

Figure 2. Aggregation of ten 10 m sub-interval readings into a single 100 m CID segment record. Per TMH 18 §19, the reported segment value for each metric is the arithmetic mean of its ten sub-intervals, IRI_seg = (1/n) Σ IRIᵢ with n = 10; the TRH 12 condition class is derived from the IRI mean against the 4.0 and 6.0 m/km thresholds.

How RoadSense produces CID exports

RoadSense parses raw .xyp profilometer output alongside GNSS survey inputs, aligns them on a shared chainage and time base, and aggregates IRI, rut, and MPD per reporting segment. The result is written as a TMH 18 §19-aligned CID file, ready for COTO submission, with a per-organisation audit trail covering every export.

What is TMH 18 Combined Instrument Data?

It is the defined exchange format, under TMH 18 §19, for reporting combined per-chainage road condition measurements — roughness, rut, macrotexture, and position — from a network-level profiler survey, so that results from different surveys and vendors remain comparable and auditable.

How do I submit profiler data to COTO?

Profiler survey results are submitted as a TMH 18 §19 CID file: a structured, per-chainage combined dataset rather than raw instrument logs. Road authorities and COTO-aligned asset management systems expect this combined format so that condition data can be loaded and compared without vendor-specific reprocessing.

What is the difference between TMH 18 and TMH 13?

TMH 13 governs how IRI roughness is measured — the Golden Car quarter-car simulation over the longitudinal profile (Sayers, Gillespie and Queiroz, 1986). TMH 18 is the data-exchange layer: it defines how measured IRI, together with rut depth, MPD and chainage referencing, is packaged per segment and submitted. In short, TMH 13 produces the number; TMH 18 §19 carries it.

References

ASTM International (2021) ASTM E1926-08(2021): Standard Practice for Computing International Roughness Index of Roads from Longitudinal Profile Measurements. West Conshohocken, PA: ASTM International.
Committee of Transport Officials (COTO) (n.d.) TMH 18: Network-level road condition data specification (draft). Pretoria: Department of Transport.
Committee of Transport Officials (COTO) (2013) TMH 22: Road Asset Management Manual (draft). Pretoria: Department of Transport.
Sayers, M.W., Gillespie, T.D. and Queiroz, C.A.V. (1986) The International Road Roughness Experiment: Establishing Correlation and a Calibration Standard for Measurements. World Bank Technical Paper No. 45. Washington, DC: The World Bank.

Browse the full standards library for related TMH 18 and TMH 13 references, or request access to discuss a CID submission for your network.