EN ISO 13473-5:2009

SLOVENSKI STANDARD
01-junij-2010
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Characterization of pavement texture by use of surface profiles - Part 5: Determination of
megatexture (ISO 13473-5:2009)
Charakterisierung der Textur von Fahrbahnbelägen unter Verwendung von
Oberflächenprofilen - Teil 5: Bestimmung der Megatextur (ISO 13473-5:2009)
Caractérisation de la texture d'un revêtement de chaussée à partir de relevés de profils
de la surface - Partie 5: Détermination de la mégatexture (ISO 13473-5:2009)
Ta slovenski standard je istoveten z: EN ISO 13473-5:2009
ICS:
17.140.30 Emisija hrupa transportnih Noise emitted by means of
sredstev transport
93.080.20 Materiali za gradnjo cest Road construction materials
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD
EN ISO 13473-5
NORME EUROPÉENNE
EUROPÄISCHE NORM
December 2009
ICS 17.140.30; 93.080.20
English Version
Characterization of pavement texture by use of surface profiles -
Part 5: Determination of megatexture (ISO 13473-5:2009)
Caractérisation de la texture d'un revêtement de chaussée Charakterisierung der Textur von Fahrbahnbelägen unter
à partir de relevés de profils de la surface - Partie 5: Verwendung von Oberflächenprofilen - Teil 5: Bestimmung
Détermination de la mégatexture (ISO 13473-5:2009) der Megatextur (ISO 13473-5:2009)
This European Standard was approved by CEN on 1 December 2009.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European
Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national
standards may be obtained on application to the CEN Management Centre or to any CEN member.

This European Standard exists in three official versions (English, French, German). A version in any other language made by translation
under the responsibility of a CEN member into its own language and notified to the CEN Management Centre has the same status as the
official versions.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland,
France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal,
Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.

EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

Management Centre: Avenue Marnix 17, B-1000 Brussels
© 2009 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 13473-5:2009: E
worldwide for CEN national Members.

Contents Page
Foreword .3

Foreword
The text of ISO 13473-5:2009 has been prepared by Technical Committee ISO/TC 43 “Acoustics” of the
International Organization for Standardization (ISO) and has been taken over as EN ISO 13473-5:2009 by
Technical Committee CEN/TC 227 “Road materials” the secretariat of which is held by DIN.
This European Standard shall be given the status of a national standard, either by publication of an identical
text or by endorsement, at the latest by June 2010, and conflicting national standards shall be withdrawn at
the latest by June 2010.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent rights.
According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following
countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Cyprus, Czech
Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,
Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain,
Sweden, Switzerland and the United Kingdom.
Endorsement notice
The text of ISO 13473-5:2009 has been approved by CEN as a EN ISO 13473-5:2009 without any
modification.
INTERNATIONAL ISO
STANDARD 13473-5
First edition
2009-03-15
Characterization of pavement texture by
use of surface profiles —
Part 5:
Determination of megatexture
Caractérisation de la texture d'un revêtement de chaussée à partir de
relevés de profils de la surface —
Partie 5: Détermination de la mégatexture

Reference number
ISO 13473-5:2009(E)
©
ISO 2009
ISO 13473-5:2009(E)
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ii © ISO 2009 – All rights reserved

ISO 13473-5:2009(E)
Contents Page
Foreword. iv
Introduction . v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions. 1
4 Significance and use of the megatexture indicators . 6
5 Measurement and data processing principles . 8
6 Test surface considerations . 9
7 Measuring equipment. 9
8 Measurement method. 10
9 Data processing. 12
10 Measurement uncertainty . 15
11 Safety considerations during measurements. 15
12 Test report . 16
Annex A (informative) Example of test report and graphical presentations. 18
Annex B (informative) Measurement uncertainty . 24
Annex C (informative) Profile asymmetry issues. 27
Bibliography . 29

ISO 13473-5:2009(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies
(ISO member bodies). The work of preparing International Standards is normally carried out through ISO
technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 13473-5 was prepared by Technical Committee ISO/TC 43, Acoustics, Subcommittee SC 1, Noise.
ISO 13473 consists of the following parts, under the general title Characterization of pavement texture by use
of surface profiles:
⎯ Part 1: Determination of Mean Profile Depth
⎯ Part 2: Terminology and basic requirements related to pavement texture profile analysis
⎯ Part 3: Specification and classification of profilometers
⎯ Part 4: Spectral analysis of surface profiles [Technical Specification]
⎯ Part 5: Determination of megatexture
iv © ISO 2009 – All rights reserved

ISO 13473-5:2009(E)
Introduction
Pavement surface texture largely influences factors such as noise emission caused by tyre/road interaction
(Reference [7]), tyre/pavement friction (Reference [8]), and comfort, as well as rolling resistance and wear of
tyres. Reliable methods of texture measurement are therefore essential.
Texture is subdivided into micro-, macro- and megatexture according to ISO 13473-2. A method for
measurement and calculation of a macrotexture indicator based on a profile measurement is specified in
ISO 13473-1. A procedure for measuring macrotexture by the volumetric patch method is described in
[2]
ISO 10844:1994 , Annex A. Currently, no reliable and practical method of measuring pavement microtexture
in situ is available. This part of ISO 13473 aims to provide means of measuring and calculating megatexture
indicators useful for pavement surface characterization.
Megatexture is an important texture range lying between macrotexture and unevenness. This type of texture
has wavelengths of the same order of magnitude as a tyre/road interface and is often a result of potholes or
'washboarding'. Some common types of singularities, such as a single depressed or protruding spot on the
pavement, will also show up in a texture profile spectrum as megatexture. Although some pavements, such as
paving stones, possess an intrinsic megatexture, it is usually an unwanted characteristic resulting from defects
in the surface.
The scope of ISO 13473 (all parts) does not include profile analysis of road unevenness, which is dealt with in
[1]
ISO 8608 .
INTERNATIONAL STANDARD ISO 13473-5:2009(E)

Characterization of pavement texture by use of surface
profiles —
Part 5:
Determination of megatexture
1 Scope
This part of ISO 13473 specifies procedures for determining the average depth or level of pavement surface
megatexture by measuring the profile curve of a surface and calculating megatexture descriptors from this
profile. The technique is designed to give meaningful and accurate measurements and descriptions of
pavement megatexture characteristics for various purposes.
Since there is an overlap between megatexture and the surrounding ranges, the megatexture descriptors
unavoidably have a certain correlation with corresponding measures in those ranges. This part of ISO 13473
specifies measurements and procedures which are in relevant parts compatible with those in ISO 13473-1,
[1] [6]
ISO 8608 and EN 13036-5 .
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
ISO 13473-2:2002, Characterization of pavement texture by use of surface profiles — Part 2: Terminology and
basic requirements related to pavement texture profile analysis
ISO 13473-3:2002, Characterization of pavement texture by use of surface profiles — Part 3: Specification
and classification of profilometers
ISO/TS 13473-4:2008, Characterization of pavement texture by use of surface profiles — Part 4: Spectral
analysis of surface profiles
ISO/IEC NP Guide 98-3:2008, Uncertainty of measurement — Part 3: Guide to the expression of uncertainty
in measurement (GUM:1995)
IEC 61260, Electroacoustics — Octave-band and fractional-octave-band filters
3 Terms and definitions
For the purposes of this part of ISO 13473, the terms and definitions in ISO 13473-2, especially the following,
apply.
ISO 13473-5:2009(E)
3.1 General terms
3.1.1
pavement texture
texture
deviation of a pavement surface from a true planar surface, with a texture wavelength less than 0,5 m
NOTE It is divided into micro-, macro- and megatexture according to 3.2.
[ISO 13473-2:2002]
3.1.2
surface profile
texture profile
two-dimensional sample of the pavement surface generated if a sensor, such as the tip of a needle or a laser
spot, continuously touches or shines on the pavement surface while it is moved along a line on the surface
NOTE 1 The profile of the surface is described by two coordinates: one in the surface plane, called “distance” (the
abscissa), and the other in a direction normal to the surface plane, called “vertical displacement” (the ordinate). An
example is illustrated in Figure 1. The distance may be in the longitudinal or lateral (transverse) directions in relation to the
travel direction on a pavement, or any direction between these.
NOTE 2 Adapted from ISO 13473-2:2002.
NOTE 3 Texture profile is similar to surface profile but limited to the texture range.
NOTE 4 “Texture wavelength” is a descriptor of the wavelength components of the profile and is related to the concept
of the Fourier transform of a time series. However, mathematically the correspondence is not exact. Note that vertical
displacement (height) has an arbitrary reference.

Key
1 vertical displacement
2 profile
3 texture wavelength
4 distance
Figure 1 — Illustration of some basic terms describing pavement surface texture
3.1.3
profilometer
device used for measuring the profile of pavement surface
NOTE 1 Current designs of profilometers used in pavement engineering include, but are not limited to, sensors based
on laser, light sectioning, needle tracer and ultrasonics technologies.
[ISO 13473-2:2002]
NOTE 2 Specifications for profilometers are dealt with in ISO 13473-3.
2 © ISO 2009 – All rights reserved

ISO 13473-5:2009(E)
3.2 Ranges of texture
3.2.1
microtexture
pavement microtexture
deviation of a pavement surface from a true planar surface with the characteristic dimensions along the
surface of less than 0,5 mm, corresponding to texture wavelengths up to 0,5 mm expressed as one-third-
octave centre wavelengths
NOTE 1 Peak-to-peak amplitudes normally vary in the range 0,001 mm to 0,5 mm. This type of texture is the texture
which makes the surface feel more or less harsh but which is usually too small to be observed by the eye. It is produced
by the surface properties (sharpness and harshness) of the individual chippings or other particles of the surface which
come in direct contact with the tyres.
NOTE 2 Figure 2 illustrates the different texture ranges, with approximate limits regarding their effects on vehicle-
pavement interactions.
[ISO 13473-2:2002]
Key
λ texture wavelength
f spatial frequency, cycles/m
sp
NOTE A lighter shade indicates a favourable effect of texture over this range, and a darker shade indicates an
unfavourable effect.
Figure 2 — Ranges in terms of texture wavelength and spatial frequency of texture and unevenness
and their most significant, anticipated effects
ISO 13473-5:2009(E)
3.2.2
macrotexture
pavement macrotexture
deviation of a pavement surface from a true planar surface with the characteristic dimensions along the
surface of 0,5 mm to 50 mm, corresponding to texture wavelengths with one-third-octave bands including the
range 0,63 mm to 50 mm of centre wavelengths
NOTE 1 Peak-to-peak amplitudes may normally vary in the range 0,1 mm to 20 mm. This type of texture is the texture
which has wavelengths of the same order of size as tyre tread elements in the tyre/road interface. Surfaces are normally
designed with a sufficient macrotexture to obtain a suitable water drainage in the tyre/road interface. The macrotexture is
obtained by suitable proportioning of the aggregate and mortar of the mix or by surface finishing techniques.
NOTE 2 Based on physical relations between texture and friction/noise, etc., the World Road Association (PIARC),
originally defined the ranges of micro-, macro- and megatexture (Reference [9]). Figure 2, which is a modified version of
the original PIARC figure, illustrates how these definitions cover certain ranges of surface texture wavelength and spatial
frequency. Note that ride discomfort includes effects experienced in and on motorized road vehicles and bicycles, as well
as wheelchairs and other vehicles used by disabled people.
NOTE 3 Adapted from ISO 13473-2:2002.
3.2.3
megatexture
pavement megatexture
deviation of a pavement surface from a true planar surface with the characteristic dimensions along the
surface of 50 mm to 500 mm, corresponding to texture wavelengths with one-third-octave bands including the
range 63 mm to 500 mm of centre wavelengths
[ISO 13473-2:2002]
NOTE Peak-to-peak amplitudes normally vary in the range 0,1 mm to 50 mm. This type of texture is composed of
wavelengths with the same order of size as a typical tyre/road interface and is often created by potholes or ripples in the
surface. It is usually an unwanted characteristic resulting from defects in the surface. Surface roughness with longer
wavelengths than megatexture is referred to as unevenness and typically takes the form of undulations in the surface.
3.2.4
unevenness
pavement unevenness
deviation of a pavement surface from a true planar surface with the characteristic dimensions along the
surface of 0,5 m to 50 m, corresponding to wavelengths with one-third-octave bands including the range
0,63 m to 50 m of centre wavelengths
NOTE 1 Pavement characteristics at wavelengths longer than 0,5 m are considered to be above that of texture and are
referred to here as “unevenness”. For airfield applications, even wavelengths longer than 50 m would be considered.
[ISO 13473-2:2002]
NOTE 2 Longitudinal unevenness is a type of surface roughness which, through vibrations, affects ride comfort in, and
road holding of, vehicles. Transverse unevenness, e.g. due to the presence of ruts, affects safety through lateral instability
and water accumulation. It is not the intention of this part of ISO 13473 to include terms which are specifically related to
[1] [3] [4] [6]
unevenness. Such terms are defined in ISO 8608 , ISO 16063-1 , ASTM E 950-98 , and EN 13036-5 .
3.3 Megatexture measurement method
3.3.1
profilometer method
method in which the profile of a pavement surface is measured and the data used for calculation of certain
mathematically defined measures
NOTE In most cases, the profile is recorded for subsequent analysis, in some cases it may be used only in real-time
calculations.
[ISO 13473-2:2002]
4 © ISO 2009 – All rights reserved

ISO 13473-5:2009(E)
3.4 Terms and parameters related to spectrum analysis of texture profiles
NOTE These terms and their applications are further described in ISO/TS 13473-4.
3.4.1
texture spectrum
spectrum obtained when a profile curve has been analysed by either digital or analog filtering techniques in
order to determine the magnitude of its spectral components at different texture wavelengths (see 3.4.2) or
spatial frequencies (see 3.4.3)
NOTE 1 A texture spectrum presents the magnitude of each spectral component as a function of either texture
wavelength or spatial frequency.
NOTE 2 Adapted from ISO 13473-2:2002.
3.4.2
texture wavelength
λ
quantity describing the horizontal dimension of the irregularities of a texture profile
[ISO 13473-2:2002]
NOTE 1 Texture wavelength is normally expressed in metres or millimetres.
NOTE 2 Wavelength is a concept commonly used and accepted in electrotechnical and signal-processing vocabularies.
Since many users of this part of ISO 13473 may not be accustomed to using the term wavelength in pavement
applications, and because electrical signals are often used in the analyses of road surface profiles, there is the possibility
of confusion. Hence the expression 'texture wavelength' is preferred here to make a clear distinction in relation to other
applications.
NOTE 3 The profile may be considered as a stationary, random function of the distance along the surface. By means of
a Fourier analysis, such a function may be mathematically represented as an infinite series of sinusoidal components of
various frequencies (and wavelengths), each having a given amplitude and initial phase. For typical and continuous
surface profiles, a profile analysed by its Fourier components contains a continuous distribution of wavelengths. The
texture wavelength in ISO 13473 (all parts) is the reciprocal of the spatial frequency, the unit of which is reciprocal metre,
equivalent to cycles per metre. See also 3.4.3.
NOTE 4 The wavelengths may be represented physically as the various lengths of periodically repeated parts of the
profile; see Figure 1.
3.4.3
spatial frequency
f
sp
inverse of texture wavelength (3.4.2)
NOTE 1 Spatial frequency is normally expressed in reciprocal metres, see also 3.4.2, Note 3.
NOTE 2 The term “frequency” used in the time domain (more precisely “temporal frequency”), corresponds to “spatial
frequency” in the space domain.
NOTE 3 Adapted from ISO 13473-2:2002.
3.5 Terms and parameters related to texture profile level
3.5.1
texture profile level
L
tx,λ
L
TX,λ
logarithmic transformation of an amplitude representation of a profile curve, Z(x), the latter expressed as a root
mean square value
NOTE 1 To distinguish between octave and one-third-octave bands, the subscript for L is written in capital letters when
it relates to octave bands, L , and in lower case letters when it refers to one-third-octave bands, L .
TX,λ tx,λ
ISO 13473-5:2009(E)
−6
NOTE 2 The texture profile level, in decibels, relative to a reference value of 10 m in one-third-octave bands having
−6
centre texture wavelength, λ, L , or the texture profile level, in decibels, relative to a reference value of 10 m in octave
tx,λ
bands having centre texture wavelength, λ, L , can be expressed by Equation (1):
TX,λ
⎫
aa
λλ
L==10 lg dB 20 lg dB⎪
TX,λ
a
a ⎪
ref
ref
(1)
⎬
aa ⎪
λλ
L==10 lg dB 20 lg dB
tx,λ
⎪
a
a
ref
ref ⎭
where
a is the root mean square (r.m.s) value of the vertical displacement, in metres, of the surface profile;
λ
−6
a is the reference value, i.e. 10 m.
ref
NOTE 3 Octave-band and one-third-octave band filters are specified in ISO 13473-2:2002, 4.4.
EXAMPLE L denotes the texture profile level for the one-third-octave band having a centre texture wavelength of
tx80
80 mm, see ISO 13473-2:2002, Table 1.
NOTE 4 Texture amplitudes expressed as r.m.s. values, whether filtered or not, can have a range of several
-5 -2
magnitudes; typically 10 m to 10 m. Spectral characterization of signals is used frequently in studies of acoustics,
vibrations, and electrotechnical engineering. In all those fields it is most common to use logarithmic amplitude scales. The
same approach is preferred in this part of ISO 13473.
NOTE 5 Texture profile levels in practical pavement engineering typically range from 20 dB to 80 dB with these
definitions.
NOTE 6 Adapted from ISO 13473-2:2002.
3.5.2
megatexture level
L
Me
special case of texture profile level with the profile passing through a bandpass filter encompassing all one-
third-octave bands within the megatexture range according to 3.2.3
[ISO 13473-2:2002]
3.6 Terms related to profilometer performance
3.6.1
evaluation length
l
length of a sample from a profile which has been or is to be analysed
NOTE Evaluation length is normally expressed in metres or millimetres.
[ISO 13473-2:2002]
4 Significance and use of the megatexture indicators
4.1 General
The indicator L shall always be calculated and reported to ensure comparability between measurements.
Me
Depending on the aim of the study in question and information already obtained (e.g. unevenness or
macrotexture measures), any or all of the three other indicators mentioned below may also be reported.
6 © ISO 2009 – All rights reserved

ISO 13473-5:2009(E)
The profilometric method described in this part of ISO 13473 enables the indicators (see 4.2 to 4.5)
characterizing the megatexture of a pavement surface to be determined.
4.2 Megatexture spectrum
This is a one-third-octave band texture spectrum covering the megatexture range and/or the adjacent ranges.
A megatexture spectrum gives a relatively complete description of the megatexture characteristics and is used
when a detailed description is needed. A spectrum covering the entire megatexture and most of the
macrotexture range is shown in Figure 3 as an example.

Key
λ texture wavelength, in millimetres
−6
L texture profile level, in decibels, relative to a reference value of 10 m
L megatexture level
Me
L texture profile level in octave bands having centre texture wavelength 63 mm
TX63
L texture profile level in octave bands having centre texture wavelength 500 mm
TX500
Figure 3 — Example of texture spectrum with indication of which bands are included
in the L and L texture levels
TX500 TX63
4.3 Megatexture level
This indicator, L , represents an overall description of defects existing in the deviation between the
Me
pavement surface and a true planar surface. Its characteristic dimensions range between 50 mm and 500 mm
along the surface (this deviation corresponds to texture wavelengths analysed in one-third-octave bands,
which include centre texture wavelengths from 63 mm to 500 mm). This indicator is used when there is a
requirement to characterize megatexture by a single measure. It covers the range of the horizontal double
headed arrow in Figure 3. For example, this parameter would be the most appropriate to identify potholes and
other irregularities (Reference [11]).
ISO 13473-5:2009(E)
−6
4.4 Texture profile level relative to a reference value of 10 m in octave bands having
centre texture wavelength 63 mm
This indicator, L , is one of the band levels derived from the above-mentioned spectral analysis. It
TX63
represents a description of the pavement defects having the shortest dimensions within the megatexture
range (deviation between the real surface and a true planar surface corresponding to texture wavelengths
analysed in one-third-octave bands which include centre texture wavelengths from 50 mm to 80 mm, being
equivalent to an octave band with a centre texture wavelength of 63 mm). This indicator facilitates the
characterization of defects which correspond approximately to the length of a normal tyre/pavement contact
patch and which, for this reason, play a direct role in the generation of tyre/road noise (Reference [7]). See the
rectangle in Figure 3 labelled L .
TX63
−6
4.5 Texture profile level relative to a reference value of 10 m in octave bands having
centre texture wavelength 500 mm
This indicator, L , is similar to L but represents a longer wavelength within the megatexture range. It
TX500 TX63
represents a description of the pavement defects having the longest dimensions within the megatexture range
(deviation between the real surface and a true planar surface corresponding to texture wavelengths analysed
in one-third-octave bands which include centre texture wavelengths from 400 mm to 630 mm, being
equivalent to an octave band with a centre texture wavelength of 500 mm). This indicator enables the
characterization of defects which can lead to tyres losing contact with the surface and therefore reduce safety
(increase in stopping distances, loss of steering control in bends, etc.), and the comfort of the driver and
passengers. This indicator is complementary to the information obtained by unevenness measurements at
short unevenness wavelengths (0,7 m to 1,3 m). See the rectangle in Figure 3 labelled L .
TX500
NOTE Both octave-band levels L and L overlap into the adjacent ranges, although two of the three one-
TX500 TX63
third-octave bands of these indicators are within the megatexture range. This is because the original definition of
macrotexture and megatexture did not consider octave and one-third-octave bands; instead “even” numbers such as
500 mm and 50 mm were chosen as the limits. Technically, this overlap is unimportant.
The values obtained by processing of the profile curve when applying this part of ISO 13473 are insensitive to
any asymmetry in the profile curve; so-called “positive” and “negative” texture. In principle, a megatexture
feature having high but narrow peaks in the positive direction can have an influence on the tyre/road
interaction which is quite different from a similar profile having inverse characteristics (the peak in the negative
direction). Such profiles, one being the inverse of the other, give the same result in terms of the megatexture
values obtained when applying this part of ISO 13473. The user is advised to observe some caution due to
this when interpreting measurement results. However, so far, very little influence of this effect in practice has
been reported and no accepted procedures to mitigate it are available. It is possible that, in any future revision
of this part of ISO 13473, such effects will be taken into account; e.g. by applying some procedure simulating
the enveloping of the texture by tyres. In the meantime, a user who wishes to consider this effect is
recommended to apply the skewness parameter as defined in ISO 13473-2:2002, 3.7.5 as a measure
supplementary to the ones in this part of ISO 13473. A type of pavement which potentially would give a high
skewness is paving stones. For such a surface and similar types, the megatexture values would need to be
used with caution.
5 Measurement and data processing principles
A vehicle-based non-contact system carries out the following operations:
a) measurement of the pavement surface profile curve;
b) preprocessing the measured profile to make it suitable for spectral analysis;
c) calculation of the texture spectrum of the profile of the longitudinal section within the megatexture
wavelength range (not mandatory if L is measured and calculated based on bandpass filtering);
Me
8 © ISO 2009 – All rights reserved

ISO 13473-5:2009(E)
d) from the spectrum, the indicator L is calculated; alternatively L is measured by means of a bandpass
Me Me
filter having suitable upper and lower limiting frequencies;
e) from the spectrum, the indicators L and L may be calculated (optional).
TX63 TX500
NOTE Calculations are normally carried out in real time, although post-processing is an option.
6 Test surface considerations
6.1 General
The measurements shall not be taken in rain or snow. The surface shall be dry during measurements, unless
it has been established that the equipment used works equally well on a wet or dry surface. In addition, the
surface shall be clean and free of all elements which could disturb the measurements.
NOTE Measurements with an optical system are not necessarily very reliable for asphalt surfaces which have
recently been paved, since these are usually exceptionally dark and shiny. If megatexture tests are carried out during or
rather soon after laying of asphalt, distortions due to temperature gradients in the air above the test surface can influence
the measurement results.
For roads open to traffic, texture normally varies over a cross-section. In this case, the lateral position of the
measurements should be in accordance with the planned use of the results.
6.2 Test lengths
It is recommended that measurements and calculations be made along the entire test section; i.e. if a profile is
recorded longitudinally along the test section, 100 % of the measured line should be utilized, if possible.
Although a continuous measurement is the ideal, the measured length shall include no less than five evenly
distributed profiles per 100 m test section. The evaluation length of each profile shall normally be 10 m.
However, in cases where stationary profilometers are used, shorter lengths may be used. The minimum
evaluation length is then 3 m for octave band analysis as well as for determination of L , or 9 m for one-third-
Me
octave band analysis.
To determine the variability in longitudinal direction, represented by longitudinal standard deviation, a number
of surface profiles, each the length of one evaluation length (refer to the previous paragraph), shall be
measured (see also 9.4).
When characterizing a long test section with relatively short sample lengths, ensure that the texture within the
sample length(s) is sufficiently representative of the total length. It is necessary to determine the minimum
number of samples necessary to minimize the effect of any suspected non-homogeneities.
7 Measuring equipment
7.1 General
Use a profilometer system which produces an electrical signal that is proportional to the distance between a
sensor reference plane and a given surface sample point. Typically, the sensor would normally be an electro-
optical device or a video camera, but other devices that comply with the requirements of ISO 13473-3 may be
used. The final output shall be linearly related to the texture profile and linearity may be obtained either in
hardware or software.
The profilometer system shall also provide means of moving the sensor along or across the surface at an
elevation (vertically) which is essentially constant over at least one full wavelength. However, this is not
applicable when the profile is produced by a technique such as light sectioning where the profile and its
reference line or plane are recorded instantaneously.
ISO 13473-5:2009(E)
The profilometer system shall meet the following specifications according to ISO 13473-3:
Mobility class: Mobile, Fast or Slow
Texture wavelength: Class EF (63 mm to 500 mm) or wider
Minimum vertical measuring range: 60 mm
Minimum horizontal uninterrupted measuring (evaluation) range: 3 m (when using octave bands) or 9 m (when
using one-third octave bands)
Vertical resolution: 0,04 mm or better
Horizontal resolution: 20 mm or better
Maximum sampling interval: 20 mm (10 mm or better recommended)
Texture wavelength range of sensor and recording system: The frequency response of the entire measuring
and data collection system shall be within ±1 dB over the entire megatexture range
Background noise: Maximum r.m.s. value: 0,05 mm (see further in ISO 13473-3:2002, Table 7)
Alignment of sensor and local slope limitation: Refer to ISO 13473-3:2002, 6.10
7.2 Sensitivity to ambient light
The output profile signal shall not change by more than 0,1 mm when changing between dark and bright
surroundings.
7.3 Sensitivity to surface optical properties
The output profile signal shall not change by more than 0,1 mm when moving the sensor between very dark
and very bright materials. It is recommended that checks be made on the system by moving the sensor over a
smooth surface having transitions from white to black to white.
NOTE Newly laid surfaces, at least if bituminous, generally have glossy and extremely dark appearances.
Profilometers relying on optical beams usually have problems with such surfaces because too little light is diffused in the
direction of the receiving element. Drop-out rates become high and there may be transients at extreme transitions
between dark and bright surfaces. The same applies to surfaces that are dark due to moisture.
7.4 Sensitivity to dampness/wetness of surface
Report whether the output profile is sensitive to the degree of moisture on the pavement, and any type or
quantity of wetness or dampness considered acceptable.
8 Measurement method
8.1 General
The measurements shall comprise the following operations:
a) testing of the sensitivity to vertical motion of the vehicle (only at certain intervals, see 8.4);
b) calibration of the profilometer system (see 8.2);
c) running the profilometer over the test section and measuring the pavement surface profile (see 8.3), using
a suitable test speed as specified in 8.3;
d) preprocessing of the profile to make it suitable for spectral analysis (see 8.5 and 8.6).
10 © ISO 2009 – All rights reserved

ISO 13473-5:2009(E)
8.2 Calibration
Calibration shall be carried out by running the sensor over a special calibration surface utilizing a well-defined
profile. The vertical deviation of the calibration surface, in relation to its theoretical profile, shall not exceed
1 % of its peak-to-peak amplitude; roughly corresponding to 0,1 dB.
Calibration procedures are not further specified here. They shall be designed such that the extra standard
uncertainty introduced by the procedure (in addition to the calibration surface, see above) is no worse than
0,1 dB.
Report the type of calibration used.
NOTE For calibration procedure and examples of calibration surfaces, refer to the principles explained in
ISO 13473-3:2002, Annex A. Consider the possibility of an adaptation to the appropriate wavelength range for
megatexture, although a calibration surface intended for the macrotexture range can be used also for megatexture if the
fundamental wavelength is at least 10 mm.
8.3 Measuring speed
Variations in the measuring speed affect the accuracy of the measured profile; see also ISO/TS 13473-4:2008,
6.1. This clause also provides requirements for a distance-based measuring system. The speed with which
the profile is traced shall be such that the requirements on sampling and bandwidth are met.
NOTE 1 The measuring speed may affect the frequency scale of any spectral analysis. The temporal frequency, f, is
given by
f = v f
sp
where
v is the speed;
f is the spatial frequency (reciprocal wavelength).
sp
NOTE 2 According to the sampling method and the existence of any low-pass filter, the speed can influence the
minimum wavelength limit.
8.4 Sensitivity to vertical motion of the vehicle
Ensure that the sensor is stable in its vertical position at least during the measurement of a full evaluation
length and for all operating speeds, or that it has some means of compensation for vertical motions. This
requires that vertical motions, e.g. those occurring at the natural suspension frequency of the sensor and/or its
carrier, shall have negligible influence, i.e. shall not violate the background noise requirements specified in 7.1.
A suitable test is to run the test vehicle (carrying the measuring device) on a smooth and even surface so that
the tyres roll over an object, having a height of 20 mm to 25 mm, a width of 200 mm and a length of 100 mm
to 150 mm, placed on the surface. Rolling over the object will excite vertical motions in the vehicle. The
difference in recorded profile with and without the object is an indication of the influence of vertical motion of
the vehicles.
The testing described in this clause is necessary when the performance of the measuring system is checked
the first time, as well as at later intervals when the vehicle suspension system performance may have
changed.
8.5 Preprocessing: Indication of invalid readings and measures to avoid their influence
The profilometer system shall have means of ensuring that invalid readings do not significantly influence the
measured results. For example when the signal becomes invalid, it may be held at the previous correct level,
or a linear interpolation may be made between the previous and following correct levels. The linear
interpolation procedure is preferred. See also ISO 13473-3.
ISO 13473-5:2009(E)
8.6 Preprocessing: Drop-out rate and validity of measurements
The measurements on a particular pavement are considered valid only if the drop-out rate for the evaluation
length in question meets one of the following criteria (Reference [10]):
a) if linear interpolation is used, a drop-out rate of up to 10 % is acceptable;
b) if linear interpolation is not used, the last valid reading before the drop-out shall be considered as a
substitute for the drop-out value(s), and in such a case the drop-out rate shall not exceed 5 %.
NOTE Drop-outs can occur. They are mainly due to specific photometrical properties in the test sur
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