Reference

Road roughness as per IRC: IRI, bump integrator and the limits

Indian roughness figures come in two units, from two kinds of instrument, against two sets of limits. This note sets out each, with the document it comes from, and how to carry a figure from one unit to the other.

IRC:SP:16-2019, Eqn. 2.1

RI = 630 × IRI^1.12

RI is bump integrator roughness in mm/km; IRI is the International Roughness Index in m/km. The equation is given for IRI below 17.

The norms

What IRC:SP:16-2019 calls good, fair and poor

Table 3.1 of IRC:SP:16-2019, Guidelines on Measuring Road Roughness and Norms (Second Revision), gives the maximum permissible roughness for expressways, national and state highways, in both units.

The same table sets the instrument: “In case of four lane divided and above corridors, roughness measurements shall be carried out using Class 1 equipment. For other corridors, the roughness measurements shall be carried out using Class 1/Class 2 or Class 3 equipment depending upon survey speed/geometric suitability.”

IRC:SP:16-2019, Table 3.1 — RI in mm/km, IRI in m/km

Maximum permissible roughness by surface type, IRC:SP:16-2019 Table 3.1
Surface	Good	Fair	Poor
Bituminous (BC, SMA, SDBC)	RI <1800IRI <2.55	RI 1800–2400IRI 2.55–3.30	RI >2400IRI >3.30
Cemented	RI <2000IRI <2.81	RI 2000–2400IRI 2.81–3.30	RI >2400IRI >3.30

The contract limits

What MoRTH’s 2023 circular sets

MoRTH’s circular of 29 March 2023 fixed one riding-quality limit for every EPC, BOT (Toll), HAM and TOT contract, as bump integrator roughness, and says it is issued “in suppression [sic] to provision of Manual and applicable IRC Standards and Guidelines of Ministry” — for contracts, it overrides them.

For flexible pavement the contract’s desirable limit, 2000 mm/km, sits above IRC:SP:16-2019’s “good” for bituminous national-highway surfaces, below 1800. Quote whichever your contract invokes, and name it.

Bump integrator roughness, mm/km, MoRTH 29 March 2023

Maximum riding quality value by pavement type, MoRTH circular of 29 March 2023, with IRI equivalents converted by IRC:SP:16-2019 Eqn. 2.1
Pavement	Desirable	Acceptable
Flexible	2,000≈ IRI 2.81*	2,400≈ IRI 3.30*
Rigid	2,200≈ IRI 3.05*	2,400≈ IRI 3.30*

* Converted by us with IRC:SP:16-2019 Eqn. 2.1, for orientation only. The circular states the limits in bump integrator mm/km and nothing else.

Where a phone fits

An estimate is not a measurement

Playcraft Chainage estimates roughness on a phone in a car mount, at 20, 100 or 1000 m segments, with quality flags on each segment for speed variation, mounting tilt and sample density. It records chainage-stamped video of the same pass.

Its quarter-car is not the Golden Car that defines the IRI (c = 6.0, k1 = 653, k2 = 63.3, μ = 0.15, simulated at 80 km/h): the app’s model uses other parameters and runs at the driving speed, so its m/km figure is an estimate, not an IRI.

It is not a certified roughness instrument of any class, and its output is not a figure to accept or reject a contract against, or to meet the Class 1 requirement above. What it is for is narrower: finding and documenting the rough segments of a route between instrument surveys, with the video showing why.

Sources

IRC:SP:16-2019, Guidelines on Measuring Road Roughness and Norms (Second Revision)Indian Roads Congress · clause 3.1.3, Table 3.1
Amendment in Roughness parameters for Flexible and Rigid pavementsMoRTH · RW/NH-33044/88/2021-S&R(P&B)/DNT · 29 March 2023
M. W. Sayers, On the Calculation of International Roughness Index from Longitudinal Road Profile, Transportation Research Record 1501eq. 3, the Golden Car data set; simulated speed 80 km/h · 1995

Next step

See it run on a call

The tool running on footage you choose, or ours
Every output file opened and explained
A plain answer on fit before commercials

See it run on a call Send us footage instead