The main technical changes in this version are: — The definition of different aims of measurement with peculiar requirements in order to optimize the instrument characteristics, measurem
Aims of measurements
At least four different aims require the measurement of the photometric quality parameters of a road lighting system:
During the final testing and commissioning phase of road lighting installations, measurements are conducted to ensure compliance with standard requirements and design expectations The results obtained from these measurements are essential for the formal approval of the road lighting installations.
During the lifespan of road lighting, measurements are conducted at set intervals to assess the decline in lighting performance These evaluations help determine maintenance needs and ensure that the road lighting installation meets standard requirements and design expectations, typically focusing on maintained values.
Adaptive road lighting involves continuous or interval-based measurements to regulate the luminous flux of luminaires This ensures that the performance of the installations remains within specified values and tolerances.
To investigate discrepancies between actual measurements and design expectations or environmental influences, measurements should be conducted as needed Different measurement procedures, requirements, and metrological characteristics of instruments must be taken into account for each specific aim.
The standard outlines measurement requirements for the final testing phase and throughout the lifespan of road lighting Specific additional measurement requirements for adaptive road lighting are detailed in Annex D, while Annex E addresses the investigation of discrepancies.
The set measurement (see 3.9) is considered as a peculiar measurement that shall follow requirements for measurement at the final testing phase
Except for the set measurement, when measurement results need to be compared they shall be carried out considering the same set of measurement points and, if required, observer position
Measurements must adhere to a comprehensive operating procedure that aligns with standard requirements and design expectations This procedure should evaluate measurement uncertainty, outline its applicability conditions, and take practical aspects into account, as detailed in the informative guidelines provided in Annexes F and G.
The objectives of the measurement shall be written in the test report (see Clause 9 and the informative Annex H)
NOTE An existing installation can have its design documentation missing In this case measurement can be done according to tender specifications.
Measurement procedures and selection of photometric instruments
Measurements can be conducted using static or dynamic measurement systems The choice of system should be based on the desired accuracy and must also take into account safety considerations, local conditions, and any specific requirements outlined in tenders.
A dynamic measurement system offers a more efficient way to assess the total length or surface area of road lighting installations compared to static systems This advantage is particularly beneficial for evaluating the uniformity of performance in road lighting or for conducting a comprehensive assessment of an entire road network at a specific moment.
NOTE Guidance on design and use of dynamic measurement systems is given in CIE 194:2011
5.2.2 General requirements on measurement procedures and on measurement devices
The measurement procedures adopted shall be suited to the purpose of the measurements
For any measurement objective, the maximum permissible expanded measurement uncertainty must be established based on national or tender specifications, taking into account its potential impact on decision-making, power consumption of road lighting systems, or other parameters outlined in EN 13201-5 Additionally, all instruments must be calibrated within their operational ranges to ensure metrological traceability.
NOTE 1 Calibration performed by an EN ISO/IEC 17025 accredited calibration laboratory guaranties this requirement
The instruments used for measurements must have metrological characteristics that align with their intended purpose Luminance should be measured using a luminance meter that meets the necessary performance standards, while illuminance must be measured with an illuminance meter that is also appropriately suited for the measurement requirements.
— 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
To ensure accurate measurements, it is essential to adjust the calibration and photometric characteristics of the detector based on the ambient temperature and humidity conditions, as well as the visible spectrum emitted by the luminaires.
Instruments for measuring photometric parameters must be characterized according to EN 13032-1, taking into account all relevant parameters and their impact on the uncertainty evaluation model.
NOTE 2 Guidance on the performance of illuminance and luminance meters is given in CIE S 023/E:2013
5.2.3 Specific requirements for luminance meter
For every type of luminance meters the influence of light sources external to the framed field shall be considered
For all luminance meters, the angular subtense of the measured road surface must not exceed 2 minutes of arc in the vertical plane and 20 minutes of arc in the horizontal plane, with a minimum angular subtense of 1 minute of arc.
According to EN 13201-3, the calculation field begins 60 meters from the observer, ensuring that the measurement areas do not overlap when viewed through a luminance meter at this distance Consequently, the maximum angle of the measurement cone is defined as specified.
NOTE 2 The minimum value of the angular subtense consider a conventional visual acuity of 1 min of arc
For measurements taken closer than the nominal positions specified in EN 13201-3 (refer to section 7.2.1), it is advised that the luminance meter's measurement cone should not exceed 30 minutes of arc Additionally, the measurement area on the road should be limited to a maximum of 0.5 meters transversely and 2.5 meters longitudinally.
For ILMDs the influence of shutter repeatability, pixel saturation and ghost images shall also be considered
Using an ILMD, the luminance at each grid point can be calculated by averaging the readings from adjacent pixels It is essential that the angular subtense conditions of the measured surfaces adhere to the specifications outlined in section 5.2.3.
Measurement uncertainty evaluation
Measurement uncertainty consists of three main components: a) the metrological characteristics of the measurement system and the impact of measurement procedures; b) the influence of the nominal characteristics and layout of the road lighting installation; and c) the effects of the instantaneous characteristics of the road lighting installation, as well as 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
Measurement uncertainty can arise from several sources, including the accuracy of measurement instruments, the precision of the coordinate reference for the measured point or area, and the influence of the measurement procedure Additionally, data elaboration methods, characteristics of road lighting installations, and the stability of photometric parameters during measurement play significant roles Other factors include electrical power supply conditions, weather conditions such as temperature and humidity, and environmental factors like nearby trees, shielding objects, and other light sources.
This European Standard does not mandate the evaluation of uncertainty contributions from the last three factors, but requires a description of their conditions in the test report This is because these factors are typically beyond the control of the measurement team, their evaluation can be challenging or costly, and road lighting installations should be assessed under real working conditions without the need for detailed quantitative knowledge Additionally, the impact of these factors on measured illuminance or luminance values is often unknown and determining it would likely require extensive and expensive measurements.
When assessing measurement uncertainties in illuminance and luminance tests, it is crucial to consider the impact of detector misalignment, such as the detector surface being out of the nominal position relative to grid points This misalignment affects the spatial variation of illuminance or luminance near the measurement point due to non-uniform light distribution, which is a characteristic of the road lighting installation rather than the measurement system or 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 ISO/IEC Guide 98-1:2009 and ISO/IEC Guide 98-3:2008.
Measured zones
The measurements shall consider the entire length of the road lighting installation and all its operating conditions (lighting classes)
When designing road lighting installations with consistent characteristics throughout, it is feasible to identify specific zones for measurement The test report must include a detailed description of the rationale, justifications, and implications of selecting these measured zones.
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.
Measured parameters
The geometrical parameters of the road in the measured area, including column spacing, carriage width, and lane width, must be accurately measured or established This is essential for defining the reference for point coordinates and determining their nominal values.
The test report must include the position, inclination, and orientation of the sensitive surface of the illuminance meter for illuminance measurements, as well as the position of the measured surface for luminance measurements, in relation to the nominal grid points.
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 for 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 test report will include essential details such as the electrical power supply conditions and the weather and environmental conditions These measurements will be provided upon request as part of a tender specification or in accordance with relevant standards (refer to Clause 8).
For M lighting classes, if tender specifications or relevant standards mandate illuminance measurement, it is essential to calculate point illuminances at the same grid points used for luminance calculations and to measure illuminance at those identical locations.
When considering M lighting classes as outlined in EN 13201-2, and if a tolerance analysis is conducted as per the informative Annex A, the tender specification may limit compliance verification to illuminance checks only.
General information regarding measurements during the lifetime of the lighting
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
Certain parameters, like the verification of electrical working conditions for installations, can often be omitted unless specified in a tender or mandated by relevant standards.
Periodic measurements of lighting performance degradation can be conducted using simplified procedures While various parameters or geometries may be assessed, it is essential to measure at least one parameter with a specific geometry for comparison during each measurement session.
The correlation between the measured parameters and normative standards must take into account prior measurements and specific conditions outlined in the road lighting installation design It is essential that all measurements are conducted consistently during each monitoring session.
Comparison with requirements
All comparisons of measured results with standard requirements or design expectations must account for the expanded measurement uncertainty For parameters requiring a value greater than or equal to a specified level, the lower limit of the expanded measurement uncertainty's coverage interval must also meet or exceed that level Conversely, for parameters that necessitate a value less than or equal to a specified level, the upper limit of the coverage interval must not exceed that level.
NOTE 1 The expanded measurement uncertainty is defined in ISO/IEC Guide 99:2007, definition 2.35
NOTE 2 The coverage interval is defined in ISO/IEC 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
At the final engineering stage, expanded measurement uncertainty is essential for optimizing management and electrical energy consumption To ensure compliance with standard requirements, measured values must be compared to the specific parameters of road lighting installations, typically following the guidelines set forth in EN 13201-2.
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
The declaration of compliance with standard requirements must include all parameters that define a specific lighting class In cases of non-conformities, it is necessary to measure additional photometric or non-photometric parameters within the installation to investigate the reasons for the discrepancies (refer to informative Annex E).
Ageing of lamps and luminaires before measurements
Measurements should be conducted after the light sources in luminaires have aged for a minimum duration specified for each lamp type in EN 13032-1.
NOTE Guidance on the ageing period for LED luminaires is under consideration.
Stabilization after switch-on
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
Regular illuminance measurements at the same location are essential to confirm that stability is achieved and maintained prior to and during the 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.
Climatic conditions
Climatic conditions should not significantly impact measurements unless intended It's important to note that certain weather conditions can lead to atmospheric absorption, which may considerably lower illuminance levels or alter the measured luminance.
If the climatic conditions during the measurement do not align with the necessary requirements for the intended purpose, the individual in charge should determine if it is appropriate to delay 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
Atmospheric light transmission significantly influences the amount of light that reaches the surface for measurement In luminance assessments, this effect extends to the light that the luminance meter receives from the surface being evaluated.
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 during measurement differ from those assessed during the road lighting design phase, the individual in charge of the measurement should consider postponing the measurements.
Road conditions
The photometric characteristics of the road surface can largely evolve over time, especially during the first three years of age of the material
Luminance measurements on new road surfaces may yield values that differ from expectations due to variations in the actual reduced luminance coefficient compared to those used during the design phase, whether measured or sourced from standard road surface tables.
In this case road surface conditions can be estimated comparing illuminance measurements and illuminance calculation (see informative Annex E).
Extraneous light and obstruction of light
To accurately assess the lighting performance of a road lighting installation, it is essential to eliminate or account for any direct or reflected light from surrounding areas Any measures taken to achieve this should be documented in the test report.
Surrounding light sources, such as shop windows, advertising signs, road signals, vehicle lights, and other road lighting installations, contribute to overall illumination This light can often be mitigated through measures like masking or switching off certain sources.
A correction of the measured values can be performed using separate measurements taken with the road lighting installation turned off Additionally, the correction for sky glow is contingent upon consistent cloudiness.
To ensure accurate measurements of unobstructed light from the installation, it is essential to choose measurement areas that are free from obstructions such as trees, parked cars, or road furniture that could cast shadows Any obstructions present should be documented in the test report.
To ensure accurate measurements, it is essential to minimize any shadow or interference from measurement systems or operators Personnel and equipment must be positioned carefully to avoid obstructing light that should reach the photometer head during illuminance measurements or the road surface during luminance measurements Additionally, care should be taken to prevent any reflections that could interfere with the light reaching these critical areas.
During the measurement phase of installations, it is essential to either eliminate extraneous and obtrusive lights or incorporate them into the overall lighting performance, following the procedures outlined in the installation design, tender specifications, or relevant standards.
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
Upon agreement with the tender, a simplified grid comprising at least 50% of the standard grid points or an alternative grid may be utilized This grid must ensure a significant distribution of points across the area designated for the complete grid, in accordance with EN 13201-3.
The accuracy in the position of the measurements points shall be included in the measurement uncertainty evaluations
During the measurement phase of a road lighting installation, various measurement points may deviate from the standard grid outlined in EN 13201-3 At the final engineering stage, a modified set of measurement points can be proposed, with accuracy assessed based on prior measurements or design data While spot checks may suffice in certain cases, it is essential that measurements encompass the entire length of the road lighting installation and account for all operating lighting classes.
Measurement of luminance
7.2.1 Location of observer (luminance meter)
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
Measurements should be conducted at a closer distance and a proportionally lower height, ensuring that the angle of view of the meter is maintained at (89 ± 0.5)° relative to the normal of the road surface.
Points on road markings, such as zebra crossings and road crossings, should be excluded from the calculation of average luminance and uniformity values These excluded points must be documented in the test report.
Certain grid points may be affected by shading from objects like trees or oil spills It is advisable to exclude these points when calculating average luminance and uniformity values, and to document them in the test report Instead, relevant specific parameters should be assessed, utilizing the algorithms outlined in Annex B Additionally, the test report must include the minimum and maximum values for the areas of framed surfaces at the grid points.
7.2.3 Measurement of the average luminance
The average luminance is calculated by averaging the luminance values measured at specific grind points or by taking 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 ILMD
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
7.2.4 Additional requirements for dynamic measurement systems
Dynamic luminance measurements shall be performed by the use of an ILMD
Effects on luminance readings from the vehicle, including shadows, light reflections, and inter-reflections, should be corrected when possible and factored into the uncertainty evaluation.
The mobile vehicle must not generate light or electronic noise that disrupts instrument readings, unless appropriate corrections are made to the readings and these adjustments are factored into the uncertainty assessment.
When a luminance detector is positioned inside a vehicle, it is essential to assess the impact of the windscreen and internal lighting on the luminance readings Any measured values must be adjusted accordingly, and these corrections should be factored into the uncertainty evaluation.
The mobile observer concept can be implemented by setting the nominal angle of view at 89° to the road surface normal The measured grid points should align with transversal lines at a distance that corresponds to the required angle of view, allowing for a tolerance of ± 2× D, where D represents the spacing between points in the longitudinal direction of the grid as specified in EN 13201-3.
During the final testing phase, the maximum distance covered during exposure must not exceed 0.5 meters, and the accuracy in defining the nominal coordinates of the measurement points should be better than D, where D represents the spacing between points in the longitudinal direction of the grid as specified in EN 13201-3.
For measurements during the lifetime of the installation, the maximum distance along which the sensors perform the measurements (during the acquisition time) shall not be greater than 2,0 m.
Measurement of illuminance
Any of four different type of illuminance shall be measured, depending on the lighting class or classes of the road lighting installation These are:
Certain grid points may be shaded by objects like trees, and it is advisable to exclude these points when calculating average and minimum illuminance and uniformity values These shaded points should be documented in the test report Instead, relevant specific parameters should be assessed, utilizing the algorithms outlined in informative Annex B.
For horizontal illuminance measurements the plane of the light sensitive surface of the photometer head shall be horizontal or parallel to the conventional road surface plane
The nominal value of the height of the plane of the light sensitive surface of the photometer head (measurement height) shall be specified in the test report (see 7.3.7 and 7.3.8)
Ideally, the light-sensitive surface of the photometer head should be at ground level; however, this is often impractical due to the thickness of the detector and the presence of supporting structures, such as gimbals.
NOTE 1 If the measurement height increases then discrepancies between the measured values and the real or calculated illuminance on the road surface increase too
The measurement height significantly impacts measurement uncertainty It is advisable to establish a correction factor for the measurement height whenever feasible Consequently, the measurement uncertainty should account for the adjusted illuminance value as well as the uncertainty associated with the correction factor.
To correct for measurement height, a factor is determined by assessing the ratio of calculated illuminance on the road surface to that on a plane at the nominal measurement height, parallel to the road surface, for each point in the utilized grid.
Hemispherical illuminance at a point can be accurately measured using an illuminance meter designed for planar illuminance The procedure involves first measuring the horizontal illuminance \( E_{h,m} \) from all luminaires at the specified point Next, the component \( E_{l,m} \) is determined for each individual luminaire by positioning the photometer head to receive light perpendicularly from that luminaire while excluding all other light sources The resulting hemispherical illuminance \( E_{hs,m} \) is then calculated based on these measurements.
E h,m is the measured horizontal illuminance from all the luminaires of the road lighting installation;
E l,m is the measured perpendicular illuminance from the l- th luminaire; n lu is the number of luminaire of the road lighting installation
The other conditions for hemispherical illuminance are the same as the condition for horizontal illuminance
The light-sensitive surface of the photometer head must be positioned approximately 1.5 meters above ground level and oriented vertically, typically facing longitudinally For further guidance, refer to EN 13201-3.
The light-sensitive surface of the photometer head must be positioned at a nominal height of 1.5 meters above ground level, in accordance with the grid points specified in EN 13201-3 It should be oriented vertically and aligned perpendicularly to the primary directions of pedestrian movement, as outlined in the guidance provided by EN 13201-3.
7.3.7 Additional requirements for static measurement systems
To ensure accurate illuminance measurements while minimizing interference from measurement systems or operators, it is advisable to use an illuminance meter equipped with a photometer head connected via a cable or a remote hold cable The cables should be long enough to allow observers to position themselves without obstructing the light that would otherwise reach the photometer head.
The use of gimbals eases the task of maintaining the photometer head at the correct inclination, with respect to the conventional road surface plane
For accurate horizontal illuminance measurements, the height should be within 200 mm of the ground In cases where the road lighting system features luminaires positioned below 2 m, the photometer head must be placed within 50 mm of the ground, or alternatively, illuminance values should also be calculated at the specified measuring height.
7.3.8 Additional requirements for dynamic measurement systems
The mobile vehicle should not obstruct lights that would typically reach the photometer head, unless such obstructions are accounted for in the measurement procedures, as seen in split detector systems.
When utilizing the split detector method, the vehicle's shielding effect is factored into the measurement process Additionally, the accuracy of the algorithm used to derive point illuminance from both front and rear detector readings will be assessed during the uncertainty evaluation.
NOTE Guidance on design, use and metrological characterization of split detector systems is given in CIE 194:2011
Vehicle-induced effects on detector readings, including shadows, light reflections, and inter-reflections between the vehicle, detector, and its case, must be corrected and factored into the uncertainty evaluation.
The mobile vehicle must not generate light or electronic noise that disrupts instrument readings, unless appropriate corrections are made to the readings and these adjustments are factored into the uncertainty assessment.
For safety reasons, the photometric head should be positioned within 300 mm of ground level Additionally, when road lighting systems feature luminaires installed at heights below 2 m, illuminance values must be calculated at the specified measuring height.
For measurements at the final testing phase, the maximum distance along which the sensors perform the measurements (during the acquisition time) shall be no greater than 0,1 m
For measurements during the lifetime of the installation, the maximum distance along which the sensors perform the measurements (during the acquisition time) shall not be greater than 1,0 m.
Measurement of Edge Illuminance Ratio (R EI )
The Edge Illuminance Ratio shall be measured following the requirements given for the measurement of horizontal illuminance and grids specified in EN 13201-3:2015, 8.6
When the measured illuminance values in the grid points are known, the edge illuminance ratio is calculated using the following formulas derived from formulas specified in EN 13201-3:2015, 8.6, Formulae (42), (43) and (44):
In certain situations, obtaining illuminance measurements in areas outside the carriageway can be challenging or even impossible When this occurs, the edge illuminance ratio cannot be determined; however, the test report should include the ratios between the measured average horizontal illuminance and the calculated average horizontal illuminance for the corresponding carriageway strips.
NOTE For example these zones are not accessible, not flat or with obstacles or shielding objects.
Measurement of the threshold increment (f TI )
If required the threshold increment can be measured with the following procedure
If n lu is the number of luminaires involved in the calculation of the threshold increment (see
According to EN 13201-3:2015, section 8.5, the threshold increment at the measurement moment is determined by taking into account the average road luminance, the illuminance generated by each luminaire on a plane perpendicular to the observer's line of sight, the height of the observer's eye, and the angle between the line of sight and the center of each luminaire, utilizing a specific algorithm.
EN 13201-3:2015, 8.5, Formulae (35), (36), (37) and (38) here repeated with the obvious changes of symbols:
L E A if (8) where the same constraints of EN 13201-3:2015, 8.5 shall be considered and:
L m is the average measured road luminance in candelas per square metre;
L v,m is the equivalent measured veiling luminance in candelas per square metre;
The equivalent measured veiling luminance, denoted as \$L_{l,m}\$, represents the luminance of the l-th luminaire in candelas per square meter The index \$l\$ refers to the specific luminaire within the summation, while \$n_{lu}\$ indicates the total number of luminaires in the road lighting installation that have an angle \$\theta_{l,m}\$ within the specified range outlined in Formulae (7) or (8).
The illuminance, denoted as \$E_{l,m}\$, represents the light intensity from the l-th luminaire on a plane aligned with the observer's eye level, measured in lux The angle \$\theta_{l,m}\$ indicates the degree between the observer's line of sight and the center of the l-th luminaire.
A y is the age of the observer, in years
In the final testing phase, the observer positions must match those used in the calculations Verification should only occur at the position that yields the highest threshold increment values, representing the worst-case scenario.
When utilizing an ILMD, the illuminance from the k-th luminaire is determined by the measured luminance and the angle \$\theta_{k,m}\$ This angle can be derived through a perspective analysis of the captured image, provided the device supports this feature, or by referencing the calculation method outlined in EN 13201-3:2015.
The uncertainty of parameters related to the ILMD is closely linked to its optical properties, including the lens's focal length and the pixel dimensions of the detector array Additionally, the optical and geometrical calibration, as well as the dimensions and layout of the road lighting installation, play a significant role It is essential that the test report includes the focal length of the lens and the pixel dimensions of the detector array for accurate assessment.
8 Measurement of non-photometric parameters
General
The selection of non-photometric measurements should be related to the purpose of the measurements (see 5.1)
It is strongly recommended where measurements are performed for comparison with requirement, detailed non-photometric measurements are required
Where the measurements are required for monitoring the state of an installation then it is possible that less detailed non-photometric measurements will suffice
Supply voltage
During measurements, it is essential to continuously monitor the supply voltage or at least check it at a significant point in the electrical installation at the start of the measurement A recording voltmeter is recommended for this purpose.
If the luminous flux emitted by the road lighting luminaires remains stable despite fluctuations in supply voltage, continuous monitoring of the supply voltage is unnecessary.
Temperature and humidity
Temperature and humidity should be measured and recorded at a height of 1 meter above ground level, starting at the beginning of the measurement period and continuing at regular intervals throughout.
Geometric data
Measurements of the installation's geometry are essential, including the plan dimensions, column heights, and outreach lengths Additionally, it is important to assess the tilt, orientation, and rotation of the luminaires if this information is relevant to achieving the measurement objectives.
Instruments for non-photometric measurements
The measurement of non-photometric parameters that are relevant for the measurement aims shall be carried out with calibrated instruments
The test report must include the decision to utilize non-calibrated instruments for certain non-photometric parameters, for which measurement uncertainty will not be assessed Additionally, quality assurance requirements for these instruments may be specified in a tender or specification request.
A comprehensive test report must include the measurement objectives, relevant information gathered during the measurement, and detailed specifications of the instruments used, including their identification and calibration conditions It should also document the weather, environmental, and electrical power supply conditions, along with a reference to the measurement procedures and data analysis, including uncertainty evaluation The report must present the measurement results along with their associated uncertainties, provide justification for any selected measurement zones, and outline actions taken to mitigate the effects of direct or reflected light Additionally, all other pertinent information should be included as specified in the previous sections.
In dynamic systems, it is essential to specify the average vehicle speed during measurements, and the evaluation of measurement uncertainty must clearly address all aspects related to movement, including any correction factors that may be applied.
The person responsible for the measurements shall sign the test report
An example of test report is proposed in the informative Annex H
Evaluation of tolerances in road lighting installation design
Tolerance analysis
A lighting project is designed to ensure that road lighting installations meet specified performance conditions, focusing on photometric quality parameters while accounting for reasonable variations in key performance-influencing factors.
Tolerance analysis is a mathematical method used to assess how various tolerances affect the expected performance of road lighting installations This includes tolerances in the manufacturing of luminaires and light sources, which are defined by product standards or manufacturers, as well as tolerances related to the layout and installation of the lighting system based on design specifications Additionally, it accounts for measurement uncertainties in the photometric characteristics of the road surface, particularly when considering luminance.
Manufacturing tolerance refers to the allowable variation in the measurements of parameters that define luminaires and light sources It is essential that the measurement uncertainty of these parameters is less than the manufacturing tolerance, as this uncertainty is factored into the specification of the tolerance interval for these products, in accordance with ISO/IEC Guide 98-4.
Tolerance analysis during the design phase is essential for minimizing installed energy while ensuring adequate lighting performance It helps in reducing luminous flux to the lowest level necessary for maintaining performance, regardless of key parameter variability Additionally, it aids in identifying the significance of specific key parameters in the degradation of photometric quality compared to design values Furthermore, tolerance analysis highlights critical parameters that need monitoring to mitigate the risk of road lighting installations failing to meet design specifications, while also clearly defining the constraints and requirements for road lighting installations.
Using tolerance analysis the lighting designer can verify and/or state the probability that the installation will satisfy the required performance characteristics
Tolerance analysis can also be used to evaluate reasons for discrepancies between measurement results and design expectations.
Parameters to be considered in the tolerance analysis
Tolerance analysis evaluates the sensitivity of nominal values of photometric quality parameters of a particular road lighting installation to the variation of the selected key parameters
Key influencing parameters are listed in Table A.1 Additional factors should be taken into account if they are known or deemed significant for the design of the road lighting system or the selected luminaire type.
Table A.1 — Main influencing parameters for tolerance analysis
Influencing parameter Definition Comment Suggested probability distribution
( z coordinate) Lighting column height tolerance (with bracket)
It can be due to tolerance in column installation but also to the column bend
Luminaire longitudinal position (x coordinate) spacing
Tolerance in the spacing between column
Tolerance in transversal position of the luminaire
Luminaire orientation Tolerance in the orientation of the luminaire
It can be due to tolerance during the installation of or to the bending of the lighting column
Luminaire tilt Tolerance in the tilt of the luminaire Normal (Gaussian) ± 1°
Luminaire rotation Tolerance in the rotation of the luminaire
Lamp luminous flux Tolerance in luminous flux output of production lamps from nominal value.
Manufacture data or standard requirements
Tolerance in the luminous intensity distribution of production luminaire from nominal value.
Manufacture data or luminaire test report
The variation can be due to manufacturing tolerances on luminaire, to the arc tube position, etc.
Supply voltage drop Tolerance in the supply voltage of single luminaires
Variation due to supply voltage drop along the line for rated supply voltage
Road surface reflection data Tolerance in Q 0 and r values These tolerance should consider also the aging or only the measurement uncertainty
Normal (Gaussian) ± 5 % (if measured) ± 20 % (if standard table are used and no other information is available)
The influence of the supply voltage of the entire road lighting installation should be evaluated separately The presence of a luminous flux controller can significantly reduce its influence.
Mathematical model for tolerance evaluations
The proposed mathematical model considers all the key parameters as uncorrelated
When the luminous intensity distribution of a chosen luminaire is measured in candelas per 1,000 lumens of lamp flux, the manufacturer must provide tolerance data related to the nominal value of the installed lamps Additionally, the tolerance of the luminous flux of the lamps can be treated as an independent variable.
When the luminous intensity distribution of chosen luminaires is measured in candelas, manufacturers must provide tolerance data that accounts for the installed lamps' tolerances In this context, the tolerance of the lamp's luminous flux is not considered a key parameter in the tolerance analysis.
Tolerance analysis involves compiling a comprehensive list of essential parameters along with their corresponding tolerances and the techniques used to assess the final uncertainty For clarity, this information is organized in Table A.2.
Table A.2 — Tolerance analysis with uncorrelated input quantities
Quantity Nominal value Tolerance Probability distribution Sensitivity coefficient Tolerance contribution
Output quantity Quantity Nominal value Combined uncertainty Final uncertainty
NOTE The symbols used in this table are described in A.4.
Modelling the tolerance analysis
The calculated quantity Y depends on N key parameters through the functional relationship
Y is the calculated or output quantity (i.e point luminance);
X i is the i-th influence or input quantity
The input quantities \(X_i\) (where \(i = 1, \ldots, N\)) are characterized by three key parameters: a) the nominal value \(x\) representing the input quantities \(X\), b) the tolerance, which defines the range of possible values for \(x_i\), and c) the probability distribution associated with \(x_i\).
When a normal (Gaussian) probability distribution can be assumed for the quantity X i then the tolerance u(x i ) is the square root of the variance of the distribution
When a rectangular probability distribution with upper limit a i,u and lower limit a i,l can be assumed then the nominal value is:
The output quantity is completely specified by two values: a) nominal value y; b) its combine uncertainty u c (y);
Where the tolerance contribution u i are:
The sensitivity coefficients can be obtained numerically using algorithms of EN 13201-3 with small variation of X i
The result of a calculation is then expressed as:
U is the final tolerance; k is called coverage factor
Conventionally k = 2 is adopted in this standard
NOTE 1 Generally the combined tolerance is calculated numerically with:
NOTE 2 A generally adopted value of the level of confidence is p = 95 %
The coverage factor \( k \) is selected based on the required confidence level \( p \) Typically, a value of \( k = 2 \) corresponds to a confidence level of \( p = 95\% \), which is applicable in most scenarios encountered in road lighting design.
General
For investigative purposes, evaluating normative photometric parameters along a specific section of a lane, rather than the entire lane, can provide valuable insights This approach helps identify the causes of diminished lighting system performance and assesses the impact of obstructions, such as trees in a boulevard, or the effects of light sources from other public and private lighting systems.
Particular luminance and uniformity
Parameters are assessed at specific points along a longitudinal line \( j \) under defined measurement conditions \( p \) These parameters include: a) the average luminance along the longitudinal line, denoted as \( L_{j,p} \); b) the maximum luminance along the longitudinal line, represented as \( L_{\text{max},j,p} \); c) the minimum luminance along the longitudinal line, indicated as \( L_{\text{min},j,p} \); d) the overall linear uniformity of luminance along the longitudinal line, expressed as \( U_{o,j,p}(L) \); and e) the longitudinal uniformity of luminance along the longitudinal line, noted as \( U_{l,j,p}(L) \).
Similarly, the same particular parameters for illuminance can be used.
Use of extended uniformity
The normative definitions of uniformities, both overall and longitudinal, require knowledge of the minimum and the maximum values of luminance or illuminance at a set of grid points
Non-homogeneous environments and road surfaces, including factors like oil spots, new pavement patches, and shadows, can significantly affect these values Additionally, uniformities assessed in various areas of the same lane may vary considerably.
Achieving uniformity through average values over a specified percentage of the total measured area or line provides a more precise representation of the actual conditions compared to relying on limit values from a single point.
To differentiate these specific uniformities and related parameters from standard ones, the term "extended" is used, along with the subscript "e(c)" added to their symbols The parameter "c" indicates the percentage of the total measured area of the surface or the total length of the line utilized for averaging the photometric parameter.
Suggested values for c can be 10 %, 5 %, 1 % and 0,5 % The appropriate choice should be made from experience and related to the particular situation
In the presence of road surface irregularities such as oil spills, dips, pavement patches, as well as obstacles like parked vehicles, trees, and leaves, or varying lighting sources, it is appropriate to use values of c = 10% or c = 5%.
On motorways and high-speed roads, low values of c are typically accurate, while main roads and urban streets adopt higher values of c due to their enhanced filtering effect Generally, when c is less than or equal to 0.3%, the difference between extended and normative parameters is negligible.
NOTE 3 The use of an ILMD for luminance measurements permits the measurement of the entire road surface and therefore allows the use of any value of c.
Evaluation of extended uniformities
To assess an extended parameter of quantity Q, such as luminance or illuminance, the measured area or line is segmented into G surfaces or segments, each with an area or length denoted as A_g (where g = 1, …, G) For each segment, a corresponding value Q_{g,p} (for g = 1, …, G) is recorded, and these values are subsequently organized and renamed for analysis.
To evaluate the extended overall uniformities U o,j,e(c) (Q), the parameter B is chosen so that:
The extended overall uniformity \( U_{o,p,e}(c)(Q) \) is defined as the ratio of two weighted average values: \( Q_a \), which represents the weighted average of \( Q \) across the first \( B \) surfaces or segments with the lowest values, and \( Q_b \), the weighted average of \( Q \) over the entire measured area.
When measuring illuminance or luminance using the moving observer technique, the areas of surfaces or lengths of segments can be treated as equal, leading to simplified formulas.
The same formulae are true for the extended overall uniformities along a longitudinal line U o,j,p,e(c) (Q)
To evaluate the extended longitudinal uniformities U l,j,p,e(c)(Q), the parameters B and M are chosen so that:
The extended longitudinal uniformity \( U_{l,j,p,e}(c) \) is defined as the ratio of two weighted average values of \( Q \): \( Q_a \), which represents the average in the first \( B \) surfaces or segments with lower \( Q \) values, and \( Q_c \), the average in the last \( (G-M) \) surfaces or segments where \( Q \) values are higher.
NOTE Also the maximum, minimum and average illuminance or luminance can be defined as extended parameters The above formula of the parameter Q can be used
(normative) Conventions for symbols of photometric quality parameters
A parameter symbol typically consists of a single letter, such as L, E, E min, or E max, and may include one or more subscripts separated by commas The first subscript, denoted as x, is used to clarify the meaning of the parameter when necessary.
— r for requirement based on lighting classes (EN 13201-2);
— d for values effectively required by the road authority (design expectations);
The subscript indicates the geometric conditions, such as alignment along a lane, while the final subscript denotes the measurement conditions, as seen in section 3.7, and may also include the evaluation conditions referenced in informative Annex B.
NOTE The normative parameters have no subscripts for measurement and evaluation conditions
To prevent confusion when evaluating measurements along a line, it is essential to specify the line by adding a subscript to the parameter symbol, such as “l1” or “l2.” The subscript can consist of letters or numbers, but the chosen convention must be clearly stated in the test report.
To ensure accurate measurements, it is essential to clearly define the measurement conditions for specific parameters The following conventions for subscripts should be used: a) for photometric quantities integrated along a segment, use the subscript "s," and specify the segment length with the photometric value; b) for photometric quantities integrated over a non-differential area, use the subscript "a," and include the area value with the photometric value.
When static measurements are carried out the acceptance area of illuminance meter is considered to be a point
In dynamic measurement systems, one dimension of the integrated area may be significantly smaller than the others, allowing finite surfaces to be treated as segments.
Understanding the effective dimensions of the measured segment or area is crucial for accurate comparisons and corrections to derive normative parameters from measured values Therefore, this information must be included in the measurement report and, if needed to prevent ambiguity, clearly indicated in the symbol of the specific parameter.
The normative lowest luminance, denoted as \$L_{\text{min,m,c}\$}, is determined by the minimum value from a set of normative luminance values \$L_m\$ measured at \$N\$ points along the centerline of a driving lane, in accordance with EN 13201-3 standards.
The value of L min,m,c,p is determined as the minimum luminance value from a specific set of luminance values L m,p, which are measured at N' designated points along the longitudinal centerline of a driving lane.
The meaning of p (number of points, geometrical measurement conditions, etc.) shall be described in
Guidelines for measurement systems for adaptive road lighting
When designing measurement systems for adaptive road lighting, it is essential to consider specific requirements that enhance or modify the general guidelines for controlling the output of luminaires.
Accurate measurement of photometric quality parameters, as outlined in EN 13201-2, requires careful selection of parameters such as luminance or illuminance, along with a thorough evaluation of measurement procedures and instrument characteristics By choosing specific parameters, it is possible to simplify the measurement system and reduce costs while still achieving the desired accuracy Additionally, it is essential to consider the measurement uncertainty of both the controlling system and the set measurement to ensure the integrity of the results.
Measuring illuminance near road surfaces presents challenges due to factors such as sensor positioning, stray light from non-road lighting sources, and dust on the detector Therefore, it is advisable to also measure road luminance at a specified angle, especially when standard lighting requirements are defined by average illuminance values.
The controlling parameters should be measured within the time constraints specified in the design or pertinent standards requirements
Other photometric or non-photometric parameters may be measured for monitoring or to increase the accuracy and reliability of the controlling system
No measured photometric quality parameters may be obtained from previous periodic measurements, from the final testing/commissioning measurement or from set measurement
Luminance measurements
The main uncertainty parameters of measuring instruments and measurement procedure to be considered are summarized in Table F.1 and in Table F.2 respectively
For measurement at the final testing phase the instability of the road lighting installation should be considered in the uncertainty evaluation
The installation short-term instability contribution in the measurement uncertainty can be obtained from several measurements of luminance at the same point
Tables F.1 and F.2 serve to highlight the significance of thoroughly analyzing the metrological characteristics of the measurement system, rather than providing a comprehensive grading of various parameters It is essential for the individual responsible for measurements to leverage their knowledge and experience to discern opportunities for enhancing measurement system performance Additionally, they should recognize which parameters are less critical and can be acknowledged without requiring precise evaluation.
Evaluating the individual influence of the parameters listed in Table F.2 can be challenging Therefore, it is more effective to assess their total impact as a single contribution to measurement uncertainty.
Table F.1 — Parameters that influence the uncertainty of luminance measurement and that are correlated to the measuring instruments Instrument Parameter Notes
Photo detector Calibration From the calibration certificate (see U cal in EN 13032-1)
Spectral responsivity To weigh the influence of the difference between the calibration source spectrum (e.g illuminant A) and the real measured spectra (see f 1 ' in EN 13032-1)
In road light spectra measurements, a correction factor can be applied, with only the uncertainty of this correction being considered Additionally, when using a traditional luminance meter, refer to section f 2 in EN 13032-1 for directional response guidelines.
If a ILMD is used, to weight the lens and shutter influence on the detector responsivity, pixel by pixel considering the direction of the grid points a
Linearity Signal linearity from the calibration certificate or by ad hoc measurement (see f 3 in EN 13032-1)
1) Detailed information on the theory of measurement uncertainty are in ISO/IEC Guide 98, ISO/IEC Guide 99 and CIE 198-
Display resolution See f 4 in EN 13032-1
If an ILMD is used the effective analogue to digital A/D converter resolution of the instrument electronics shall be considered
Pixel saturation in the measured zone can be affected by the saturation of pixels outside this zone when using an ILMD Additionally, framed luminous sources in the surrounding field influence the measured zone, as indicated by f 2,u in EN 13032-1 Conversely, unframed luminous sources present in the environment also impact the measured zone Furthermore, the influence of detector noise and dark current values, along with repeatability, is significant; when an ILMD is employed, values are obtained pixel by pixel from dark frames.
The impact of being out of focus occurs when the measured zone is not positioned at the correct distance, as referenced in f 12 of EN 13032-1 Additionally, non-uniform illumination within the acceptance areas of the framed zone can significantly affect measurement accuracy.
The design of certain photometer heads results in a notable dependence of responsivity, including relative spectral responsivity, on the position of incident light within the acceptance area (refer to figure 9 in EN 13032-1).
If an ILMD is used, only the detector surface were the measuring zone is framed shall be considered
Other parameters defined in EN 13032-1 The influence of the other performance parameters specified in
EN 13032-1 as a whole or parameter by parameter a Guidance on the characterization of ILMD is under consideration
Table F.2 — Parameters that influence the uncertainty of luminance measurement and that are correlated to the measurement procedure
Point identification Influence of the uncertainty in the point coordinates
If road markers are used, accuracy of alignment and positions of the markers
Influence of the perspective correction algorithm
If a perspective correction algorithm is used, accuracy of the calculated measurement point coordinates derived from the accuracy of the road reference point and of the perspective correction algorithm
Measurement area Influence of the effective area of the point of measurement
Dimension of the framed surface used to acquire the point of luminance
Real position Influence of the real camera position compared to the nominal position
Influence of tolerances respect to the nominal position required in this standard or Influence of the different detector position
F.1.2 Additional uncertainty sources for dynamic systems
Many sources of uncertainty are more critical in dynamic measurement systems than in static ones and some sources are typical of dynamic systems
The vehicle speed is an important factor The use of particular parameters (see 3.5) is suggested to better describe the measured quantities
If only a single transit is conducted, only one measurement for the point can be obtained To address any short-term instability during installation, it is essential to gather or estimate data from ad hoc measurements taken in the installation area for a duration that is at least equal to the time spent on dynamic measurements of the same installation.
Table F.3 outlines specific sources of uncertainty related to measuring instruments, while Table F.4 addresses uncertainty sources associated with measurement procedures These tables serve as supplementary information to Tables F.1 and F.2.
Table F.3 — Additional parameters of Table F.1 that influence the uncertainty of luminance measurement carried out with dynamic systems
Photo detector Influence of movement The measured area is longer for the movement of the vehicle For example at 90 km/h and with exposure time of 20 ms the space is 0,5 m
Table F.4 — Additional parameters of Table F.2 that influence the uncertainty of luminance measurement carried out with dynamic systems
Point identification Influence of the uncertainty in the point coordinates
Accurate positioning of dynamic system detectors relative to the initial reference point is crucial for effective measurements This positioning directly impacts the measurement area and the influence of the effective area at the measurement point.
Dimension of the framed surface used to acquire the point of luminance shall consider the vehicle movement
Real position Influence of the real camera position compared to the nominal position
Influence of tolerances with respect to the nominal position required in this standard Both longitudinal and transverse positions are important Detector tilting affects the measurement distance
F.1.3 Evaluation of point luminance uncertainty
In this example the uncertainty of the measurement system is considered, and not that of the influence of the road lighting installation, measurement point position and weather
The proposed measurement procedure model involves subtracting the effects of dark image readings, internal and external sources, and ghost images from the detector readings The resulting value is then multiplied by a calibration coefficient and additional correction factors related to the parameters outlined in CIE S 023/E:2013, which typically have a value of one.
The point measured luminance L m is:
R m is the detector reading (measure image);
R d is the detector reading (dark image);
R i is the signal due to luminous sources inside the frame;
R o is the signal due to luminous sources outside the frame;
R g is the signal due to ghost images;
K cal is the detector calibration; f ' 1
K is the detector directional responsivity; f 3
K is the detector A/D real resolution; f 12
K is the influence of focusing distance; f cie
K is the influence of other, generally less important performance parameters described in
NOTE 1 In well-designed measurement system R i , R o , and R g are usually negligible, compared to R m and R d therefore only their uncertainty is important
NOTE 2 In dynamic measurement systems only one measurement is carried out so the standard uncertainty of
R m is equal to the repeatability of the luminance meter
NOTE 3 Usually in ILMD all the parameter of the proposed model (Formula F.1) are different from pixel to pixel.