International roughness index

The IRI is defined as an index computed from a longitudinal profile measurement using a reference mathematical RTRRMS (a quarter-car simulation) for a standard simulation speed of 80 km/h (ASTM E 867 2012 Sayers 1986b). 

The IRI and its algorithm to be computed from profile data were the outcome of the International Road Roughness Experiment conducted in Brazil and are described in detail in the technical reports by Sayers et al. (1986a,b). 

IRI can be interpreted as the output of a response-type measuring system where the physical vehicle and instrumentation are replaced with a mathematical model. The units of slope correspond to accumulated suspension motions (e.g. metres), divided by the distance travelled (e.g. kilometres). 

The IRI is portable in that it can be obtained from longitudinal profiles obtained with a variety of instruments. The IRI is stable with time because true IRI is based on the concept of a true longitudinal profile, rather than the physical properties of a particular type of instrument (ASTM E 1926 2008). The instruments used for the collection of roughness data are characterised into four classes as defined by Sayers et al. (1986b). 

When profiles are measured simultaneously for both travelled wheel tracks, then the mean roughness index (MRI) is considered to be a better measure of road surface roughness than the IRI for either wheel track. The MRI scale is identical to the IRI scale. Relevant guidance on the calculation of IRI and MRI can be found in ASTM E 1926 (2008) or AASFITO R 43 (2013). 

---

The relative displacement devices (high-speed evenness meters) can be response-type device accelerometers mounted to a vehicle or wheel trailer. Such devices are as follows TRRL Bump Integrator (BI), Mays ride meter, NAASRA roughness meter, Road meter PCA, ROMDAS bump integrator, all response-type devices, Canadian ARAN, Road Surface Tester (RST-SAAB) and accelerometer-type devices. When these devices are used, proper calibration of the equipment is vital and the output is best expressed in IRI (International Roughness Index). 

The surface evenness, determined using the International Roughness Index, for the abovemen-tioned site classes is 0-1.3,1.3-2.6 and 2.6-4.0 m/km, respectively. Evenness may be expressed in terms of APT rating (French profilometer) and respective range values are given in COST 232. 

The determination of PSI using the above equations provided the ability to quantify more objectively the pavement condition from condition surveys. Many organisations in the United States and in other countries have adopted the PSI approach for periodical evaluation of the pavement condition (road network) aiming to prioritise and organise maintenance and rehabilitation works. Others have modified the PSI equations according to their own findings and needs, for example, inclusion of International Roughness Index (IRI) measurements (Hernan de Solminihac et al. 2003). 

Al-Omari B.H. and M. Darter. 1994. Relationships between International Roughness Index and present serviceability rating. Transportation Research Record, No. 1435, pp. 130-136. Washington, DC TRB, National Research Council. 

ASTM E 1926. 2008. Standard practice for computing International Roughness Index of roads from longitudinal profile measurements. West Conshohocken, PA ASTM International. 

Priem H. 1989. NAASRA Roughness Meter Calibration via the Road-Profile-Base International Roughness Index (IRI). Research report ARR No. 164. Melbourne, Australia Australian Road Research Board. 

This edition and the completely revised five-volume Third Edition (1971) established the Colour Index as the leading reference work for the classification of colorants, fully justifying the cognomen International belatedly added in 1987. The fourth revision (1992) of the Third Edition consisted of nine volumes. The original data on technical properties (Volumes 1-3) and chemical constitution (Volume 4) was supplemented (Volumes 6-9) at roughly five-year intervals. 

Unique information about the unit cell in quasi-crystaUine monolayers can be obtained from X-ray °, neutron , heUum or low energy electron diffraction (LEED) data. In the grazing incidence X-ray diffraction (GIXD) experiment the beam is directed at the coated surface at a low angle and experiences total internal reflection from the metal support underneath the monolayer. The analysis of reflectivity and diffraction pattern of this reflected beam provides information about the molecular structure of the crystalline films, the thickness and refractive index of the layers and the roughness of the surface s . These experiments, however, require sophisticated and expensive equipment and are not therefore used routinely for monolayer characterization. 

Reflectance techniques may be used for samples that are difficult to analyze by the conventional transmittance method. In all, reflectance techniques can be divided into two categories internal reflection and external reflection. In internal reflection method, interaction of the electromagnetic radiation on the interface between the sample and a meditnn with a higher refraction index is studied, while external reflectance techniques arise from the radiation reflected from the sample surface. External reflection covers two different types of reflection specular (regular) reflection and diffuse reflection. The former usually associated with reflection from smooth, polished surfaces Hke mirror, and the latter associated with the reflection from rough surfaces. 

Although noitfadiative, the surface mode can nevertheless participate in absorption and emission of electromagnetic radiation under special artificial conditions. These include a rough surface (Section 3.9.5) or ATR conditions, under which photons are not coupled directly to the active medium-dielectric interface but via the evanescent tail of the radiation, which is totally reflected internally at the base of a high-index prism (with pr > ei) [16, 36]. In the latter case, the radiation is characterized by a larger momentum (Fig. 3.6, long-dashed line) and can... 

As implied by Eq. 15.2, all the materials in Table 15.1 must have higher refractive indices than the material with which they are in contact. Materials that are commonly used as windows in the mid-infrared [e.g., KBr n = 1.53) and KCl ( i = 1.45)] are not included in this list, as their refractive indices are too low for use as IREs. Because the refractive indices of KBr and KCl are roughly equal to the refractive index of organic compounds, total internal reflection will not be observed. In this case, radiation passes directly through the IRE and sample without regard to the angle of incidence. In other words, these materials are better suited for use as infrared-transmitting windows than as internal reflection elements. 

---