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NOTE Guidance on design and use of dynamic measurement systems is given in CIE 194:2011.

The measurement procedures adopted shall be suited to the purpose of the measurements.

For a given measurement aim, the maximum acceptable value of the expanded measurements uncertainty shall be defined considering national or tender requirements and upon the evaluation of the influence this uncertainty can have on the decision taken using the measurement results or on the power consumption of the road lighting installation or any other parameters defined in EN 13201-5.

All instruments shall be calibrated in the ranges used to assure their metrological traceability.

NOTE 1 Calibration performed by an EN ISO/IEC 17025 accredited calibration laboratory guaranties this requirement.

The metrological characteristics of the instruments used shall be suited to the purpose of the measurements. Luminance shall be measured with a luminance meter which has a performance suitable for the purpose of the measurements. Illuminance shall be measured with an illuminance meter which has a performance suitable for the purpose of the measurements:

• for the measurement of horizontal and vertical illuminance a photometer head for the measurement of planar illuminance is required;

• for semicylindrical or hemispherical illuminance a photometer head designed for this purpose is required.

The instruments metrological performances shall be evaluated for the specific conditions of the application.

Therefore if needed, the calibration and photometric characteristics of the detector used shall be corrected taking account of the ambient temperature and humidity conditions during measurements and the spectra emitted in the visible region by the luminaires.

Instruments used for measurement of photometric parameters shall be characterized in accordance with EN 13032-1 for all the relevant parameters and their influence shall be considered in the uncertainty evaluation model.

NOTE 2 Guidance on the performance of illuminance and luminance meters is given in CIE S 023/E:2013.

For every type of luminance meters the influence of light sources external to the framed field shall be considered.

For every type of luminance meter, in every case of grind point measurement the angular subtense of the measured road surface shall be not be greater than 2 min of arc in the vertical plane and not greater than 20 min of arc in the horizontal plane. The minimum angular subtense shall be no lower of 1 min of arc.

NOTE 1 The field of calculation specified in EN 13201-3 commences 60 m from the observer. This means that to prevent overlap of the measurement areas as seen through a luminance meter set at this distance, the maximum value of angle of the measurement cone has the value indicated above.

NOTE 2 The minimum value of the angular subtense consider a conventional visual acuity of 1 min of arc.

If the measurement is carried out at a closer distance respect to the nominal positions of the observer given in EN 13201-3 (see 7.2.1) it is recommended that the measurement cone of the luminance meter should not exceed 30 min of arc, and the size of the measurement area on the road should not be greater than 0,5 m transversely and 2,5 m longitudinally.

For ILMDs the influence of shutter repeatability, pixel saturation and ghost images shall also be considered.

If an ILMD is used the luminance for each grid point may be determined by averaging the reading of adjacent pixels. In every case the conditions on the angular subtense of the measured surfaces shall comply with requirements given in 5.2.3.

5.3 Measurement uncertainty evaluation

The measurement uncertainty can be considered as having three groups of components:

1. Those concerning the metrological characteristics of the measurement system and the influence of measurement procedures;

2. Those concerning the influence of the nominal characteristics and layout of the road lighting installation being measured;

3. Those concerning the influence of the instantaneous characteristics of the road lighting installation being measured, and of the weather and environmental conditions.

These three groups shall be separated because the last one can change significantly from one measurement to another, while the influence of the measurement system can remain substantially constant.

The various sources of measurement uncertainty can be classified as:

1. accuracy of measurement instruments;

2. accuracy of the coordinate reference of the measured point or area (if relevant);

3. influence of the measurement procedure;

4. influence of data elaboration methods;

5. road lighting installation characteristics and stability of the photometric parameter’s during measurement;

6. electrical power supply conditions;

7. weather conditions (temperature, relative humidity, wind velocity, etc.);

8. environmental conditions (presence of trees, shielding objects, disturbing light sources, other lighting installations, etc.).

For practical reasons this European Standard does not require the evaluation of the uncertainty contribution of the last three, but only a description in the test report of their conditions, because:

9. they are not usually under the control of the measurement team;

10. their evaluation or measurement can be difficult or expensive;

11. the road lighting installation should normally be evaluated in real working conditions that do not need to be quantitatively known in detail;

12. the influence of these matters on the measured illuminance or luminance value is generally not known and it is likely to be impossible to determine without a laborious and expensive set of measurements.

If point values or uniformities are given in the test report, the influence of the detector misalignment (e.g. the detector surface is not in the nominal position with respect to grid points) for illuminance measurements or position and dimensions of the framed surface for luminance measurements shall be considered when evaluating measurement uncertainties. This correlation is a characteristic of the road lighting installation (spatial variation of illuminance or luminance near the point due to non-uniform light distribution) and not of the measurement system or measurement procedures.

This contribution to the measurement uncertainties need not be considered for average values.

Guidelines for the evaluation of measurement uncertainty in road lighting installation characterization are given in the informative Annex F.NOTE Guidance on the calculation of measurement uncertainty is given in IS0/1EC Guide 98-1:2009 and IS0/1EC Guide 98-3:2008.

The measurements shall consider the entire length of the road lighting installation and all its operating conditions (lighting classes).

If the road lighting installation characteristics are designed as constant for the total length of the installation, it is possible to select a relevant number of zones and to carry out measurements only in these zones (measured zones). In this case a description of the reasons, justifications and consequences of this choice shall be written in the test report.

NOTE One of the most common reasons for the selection of particular measured zones is the supply voltage drop in the power supply electrical line.

The road geometrical parameters in the measured zone (column spacing, carriage and lane width) shall be measured or known to allow for defining the reference for point coordinates and the nominal values of point coordinates.

The position, inclination and orientation of the sensitive surface of the illuminance meter (for illuminance measurement) or of the position of measured surface (for luminance measurement) with respect to the nominal grid points shall be recorded in the test report.

For illuminance measurement the z coordinate (height of the light sensitive surface of the detector with respect to the road surface) shall also be specified. ..

NOTE These parameters are specified using their nominal value and tolerances, or the measured values with uncertainty.

Measurement for the verification of compliance with standard requirements shall consider all the photometric quality parameters for the pertinent lighting class/classes.

A reduced set of parameters may be adopted if agreed with the purchaser or operator and if this choice is described in the road installation design.

Measurement/or the verification of compliance with design expectation shall consider a congruent set of parameters as specified and evaluated in the road lighting installation design.

EXAMPLE This set can specify the measurement of illuminance in grid points instead of the road surface average luminance and the calculation of uniformities considering these values.

The following additional points shall be described in the test report:

1. electrical power supply conditions,

2. weather and environmental conditions,

and shall be measured if requested as part of a tender specification or required as part of a pertinent standard (see Clause 8).

If tender specification or pertinent standard require the measurement of illuminance, as a preliminary verification step for M lighting classes, point illuminances at the same points of the grid used for luminance calculation shall be calculated for M lighting classes and illuminance measured at the same points.

If M lighting classes (see EN 13201-2) are considered and the project has a tolerance analysis (see the informative Annex A) tender specification may restrict the verification of compliance with standard requirements to the illuminance verifications only.

Measurements during the road lighting lifetime are usually carried out before or after installation maintenance, in accordance with design requirements.

A limited set of measured parameters and simplified measurement geometry may be selected in accordance with the design specifications or tender requirements.

The determination of some parameters can even be avoided, such as the verifications of the electrical working conditions of the installation, unless requested as part of a tender specification or required as part of a pertinent standard.

If measurements are carried out at pre-determined intervals or periodically to quantify the degradation of the lighting performance they may be done using simplified procedures. Different set of parameters or geometries may be measured but at least one parameter with a given geometry shall be measured for comparison purpose each time measurements are taken.

Correlation between the parameters measured in these conditions and the normative parameters shall consider previous measurements or specific measurement conditions describe in the road lighting installation design. However, all measurements shall be carried out in a compatible way each time monitoring is carried out.

All comparison of measured results with standard requirements or design expectations shall be carried out considering the expanded measurement uncertainty of the measure:

1. for parameters that require a value greater or equal to a given level, the lower limit of the coverage interval of the expanded measurement uncertainty shall be greater or equal to the given level;

2. for parameters that require a value lower or equal to a given level, the upper limit of the coverage interval of the expanded measurement interval shall be lower or equal to the given level.

NOTE 1 The expanded measurement uncertainty is defined in 1S0/1EC Guide 99:2007, definition 2.35.

NOTE 2 The coverage interval is defined in ISO/1EC Guide 99:2007, definition 2.36.

NOTE 3 Guidance on the role of measurement uncertainty in conformity assessment is given in

ISO/IEC Guide 98-4.

This standard does not give requirements for the range of acceptable values of measurement uncertainty.

The expanded measurement uncertainty required for measurements can be indicated at the final engineering stage as requirements for optimization of management or electrical energy consumptions.

For the verification of compliance with standard requirements the measured values shall be compared to the specific road lighting installation parameters. Generally the requirement of EN 13201-2 shall be used.

For the verification of compliance with design expectation the measured values shall be compared to the congruent set of parameters specified and evaluated in the road lighting installation design.

If specific design parameters are given in the tender they shall be used.

In the declaration of compliance with standard requirements all the parameters that identify a given lighting class shall be mentioned. Non-conformities require the measurement of other photometric or not-photometric parameters in the installation, if the reasons of the discrepancies are to be investigated (see informative Annex E).

6. Measurement conditions

   1. Ageing of lamps and luminaires before measurements

Generally measurements shall be carried out after a period of ageing of the light sources installed in luminaires of not less than the period specified, for a given lamp type, in EN 13032-1.

NOTE Guidance on the ageing period for LED luminaires is under consideration.

Luminaires require a period of time for their light output to stabilize and all measurements shall be done after this stabilization period.

NOTE 1 Guidance on the stabilization period for different lamp typologies is given in EN 13032-1.

NOTE 2 Guidance on the stabilization period for LED luminaires is under consideration.

Monitoring readings shall be taken if there are concerns about the stability of the road lighting installation during the period of measurement.

EXAMPLE Illuminance measurements at the same location or locations should be taken at regular time intervals to ensure that stability has been reached and maintained before and during the period of definitive light measurements of the road lighting installation.

NOTE 3 Depending on the type of lamps and road lighting installation adequate information is obtained by monitoring the supply voltage.

The climatic conditions should be such as not to affect measures significantly, unless this is intended to.

NOTE In some weather conditions, atmospheric absorption significantly reduces the illuminance level or modifies the luminance measured.

If the climatic conditions at the measurement time do not represent the conditions required for the measurement aim, the person responsible for the measurement should decide whether to postpone the measurements.

High or low temperatures may affect the calibration and the accuracy of the light measuring instruments.

Condensation or moisture on light transmitting surfaces of measuring instruments or on their electric circuits may affect their accuracy.

High wind speeds may make the measuring instruments vibrate or oscillate.

The influence of climatic conditions on the instrument performances shall be considered using correction factors. These uncertainties shall be considered in the measurement uncertainty evaluation.

If the climatic conditions are outside the range of the known correction factors the person responsible for the measurement shall postpone the measurements.

High or low temperatures or high wind speeds may affect the light output of thermally sensitive lamps or luminaires.

High wind speeds may make the luminaires oscillate.

The light transmission of the atmosphere will affect the light reaching the surface to be measured, and in the case of luminance measurements the light reaching the luminance meter from the surface to be measured.

The climatic conditions should be such as not to affect the measurements significantly, unless this is intended.

Luminance measurements shall only be performed when the road is dry when considering the M Classes requirements for dry conditions.

NOTE When taking dry surface measurements even a slight dampness of the road surface significantly affects the luminance of the road surface.

If the climatic conditions at the measurement time do not represent the conditions evaluated in the design phase of the road lighting installation, the person responsible for the measurement should decide whether to postpone the measurements.

The photometric characteristics of the road surface can largely evolve over time, especially during the first three years of age of the material.

In case of luminance measurements on a new road surface, measured values can be different from the expected ones because the actual reduced luminance coefficient is different from that used at the design stage (measured or obtained from standard road surface tables).

In this case road surface conditions can be estimated comparing illuminance measurements and illuminance calculation (see informative Annex E).

When measurements are intended to record the lighting performance of the road lighting installation only, direct or reflected light from the surrounds should be prevented or accounted for. Action taken to do this should be recorded on the test report.

NOTE 1 Light from the surrounds includes light from shop windows, advertising signs, road signals, lights on vehicles, other road lighting installations, sky glow, reflections from snow at the road side, etc. This lighting can sometimes be prevented, masked or switched off.

NOTE 2 A correction of the measured values can be made which is based on separate measurements taken with the road lighting installation switched off. A correction for sky glow depends on the cloudiness not being variable.

When measurements are intended to record the unobstructed light from the installation, if possible measurement areas should be selected which are free of obstructions that may produce shadows. These may include trees, parked cars, or road furniture. The presence of obstructions should be recorded in the test report.

Any shadow or interference from measurement systems or operators shall be reduced to the minimum possible. Care shall be taken that personnel making the measurements or equipment they are using does not obscure light that would otherwise reach the photometer head (illuminance measurement) or the measured road surface (luminance measurement) or reflect light that would otherwise not reach the photometer head or the measured road surface

When performing measurements during the lifetime of the installations, extraneous and obtrusive lights may be avoided or may be considered part of the global lighting performance in accordance with procedures described in the installation design, as part of a tender specification or pertinent standard.

6. Photometric measurements

   1. Location of grid points

The nominal position of the grid points at which measurements are taken shall agree with those given in EN 13201-3.

If agreed with the tender, a reduced set of points, using at least 50 % of the standard grid points or an alternative grid can be adopted. This simplified grid or the alternative grid should have a significant distribution of points over the area used to define the full grid (see EN 13201-3).

The accuracy in the position of the measurements points shall be included in the measurement uncertainty evaluations.

When doing measurements during the lifetime of the road lighting installation, different measurement points may be taken with respect to the standard grid (see EN 13201-3). In this case a reduced or extended set of measurement points may be considered or suggested at the final engineering stage and accuracy evaluated following previously measured or design data. In some situations spot checks may be sufficient, however, the measurements shall consider the entire length of the road lighting installation and all its operating lighting classes.

For luminance measurement, the nominal positions of the observer shall agree with those given in EN 13201-3. The accuracy in the position of the observer shall be included in the measurement uncertainty evaluations.

Measurement can be carried out at a closer distance and at a proportional lower height so that the angle of view of the meter shall be at (89 ± 0,5)° to the normal to the road surface.

If some points of the grid are located on road markings (zebra, road crossing) they shall not be considered in the determination of the average luminance and the uniformity values. These points shall be recorded in the test report.

Some points of the grid can be located in the shade of an object (tree) or oil spread, etc. In such cases, it is recommended not to consider these points in the determination of the average luminance and the uniformity values and to recorder these points in the test report. Alternatively the appropriate particular parameters should be evaluated. The algorisms of the informative Annex В can be used.

The minimum and maximum values of the areas of framed surfaces at grid points shall be given in the test report.

The average luminance is obtained as the average value of the luminances measured at the grind points (see 7.1 and 7.2.2) or by means of a single reading of the relevant area of the road surface.

For the measurement of average luminance by means of a single reading, the meter shall be an 1LMD.

NOTE If a ILMD is not used, the luminance measurement gives, in effect, perspective weighting to each point and evaluates also the road surface between grid points.

Dynamic luminance measurements shall be performed by the use of an ILMD.

Any effects on the luminance readings generated by the vehicle, such as shadows cast by the vehicle, light reflected from the vehicle to the luminance meter, inter-reflection shall be corrected, if possible, and shall be considered in the uncertainty evaluation.