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Roadway Standards - Calculation Metrics

AGi32 allows you to specify roadway calculation grids according to the definitions in ten roadway standards in use around the world. These standards are:

- IESNA RP-8-00 (reaffirmed in 2005)
- IES RP-22-11
- CIE 140-2000
- Australia/New Zealand Standard 1158.2-2005, including Cat. P
- BSEN 13201-3.2003
- ABNT NBR5101-2012
- Australia 1158.2-2005-SAASTAN

This table shows the calculation metrics that are defined in each standard:

IESNA RP-8 | IES RP-22 | CIE 140-2000 | BSEN 13201-3 .2003 | ABNT NBR5101-2012 | Australia 1158.2-2005 | New Zealand 1158.2-2005 | |
---|---|---|---|---|---|---|---|

Pavement Luminance | X | X | X | X | X | X | X |

Illuminance | X | X | X | X | X | X | X |

Veiling Luminance | X | X | X | X | |||

Visibility Level (STV) | X | ||||||

Longitudinal Uniformity | X | X | X | X | X | ||

Vertical Illuminance | X | X | X | ||||

Semi-cylindrical Illuminance | X | X | X | ||||

Hemispherical Illuminance | X | ||||||

Surround Illuminance | X | X | X | X | X | ||

Veiling Luminance w/TI | X | X | X | X | X |

Definitions of these metrics are provided below, listed by standard.

Selecting Calculation Metrics for a Custom Standard

In creating a custom standard, you may select from the metrics listed in the Roadway Standard - Calculation Metrics dialog. Depending on the standard that you start with, certain metrics will be checked by default. You may check or uncheck any of the metrics and then click OK. The selected (checked) metrics will be listed in the Calculation Metrics field on the left side of the Roadway Standards dialog.

See Roadway Standards - Configure - Concepts for more information on creating custom standards.

Calculation Metric Definitions, by Standard

AGi32 creates the calculation grids used to calculate Pavement Illuminance, Luminance and Veiling Luminance per the latest revision of RP-8 (RP-8-00).

Average Pavement Luminance (L_{avg})
- Luminance on the pavement is
based on the quantity and direction of light, observer location, and the
pavement reflectance characteristics. The overall average luminance of the road surface as observed from a
specific point in cd/m^{2}. Metric units are used regardless of current
settings. Observer position is 1.45 meters above the pavement surface and
83.07 meters back from each computation point along a longitudinal line
parallel to the direction of travel. Observer line of sight is 1 degree
below horizontal. Observer position changes relative to the curb line
to align with each row of calculation points. A Roadway Luminance grid represents the calculation points for a single
directional flow of traffic. To consider the entire roadway, a calculation
grid should be created for each direction of traffic flow. The directional flow
of traffic is determined by the specified order of the curb points defining the
length of the roadway. Traffic flows in the direction of first point
to second point. The third point defines the width of the roadway
from curb to curb in one direction of traffic flow.

**Illuminance -** Illuminance is a measure of the lumens incident on the pavement divided by the area. The units are lumens per square foot (footcandles) or lumens per square meter (lux). Illuminance is not impacted by the pavement's surface type or the angle of
observation.

Veiling Luminance (L_{v}) - A measure
of disability glare, veiling luminance is a luminance superimposed over
the eye's retinal image that is produced by stray light within the eye. In the
IES method, L_{v} is computed at the same points as the pavement luminance
with the observer 83.07 meters back from each computation point. Observer
line of sight is 1 degree below horizontal at 1.45 m above the road surface.

Veiling Luminance ratio - The
IES method uses the maximum value of Veiling Luminance (L_{v,max}) divided by
the Average Pavement Luminance (L_{avg}) as a measure of the disability glare
produced by a lighting system.

Weighted Average VL (STV) – A measure of the visibility of small targets in the roadway considering the target luminance, veiling luminance and the background pavement luminance against which they are seen. The weighted average of all Visibility Levels (STV) is given. An Visibility Level grid may be included in the calculated results. It is recommended that this grid be examined, as it provides information about contrast bands . When considering Visibility Level and STV, designs are created that produce negative and positive contrast, all positive contrast, and all negative contrast. The weighted average of the calculated Visibility Levels is displayed as the STV.

IES, RP-22-11

AGi32 creates the calculation grids used to calculate Pavement Illuminance, Luminance and Veiling Luminance per the latest revision of RP-22 (RP-22-11).

Average Pavement Luminance (L_{avg})
- Luminance on the pavement is
based on the quantity and direction of light, observer location, and the
pavement reflectance characteristics. The overall average luminance of the road surface as observed from a
specific point in cd/m^{2}. Metric units are used regardless of current
settings. Observer position is 1.45 meters above the pavement surface and
83.07 meters back from each computation point along a longitudinal line
parallel to the direction of travel. Observer line of sight is 1 degree
below horizontal. Observer position changes relative to the curb line
to align with each row of calculation points. A Roadway Luminance grid represents the calculation points for a single
directional flow of traffic. To consider the entire roadway, a calculation
grid should be created for each direction of traffic flow. The directional flow
of traffic is determined by the specified order of the curb points defining the
length of the roadway. Traffic flows in the direction of first point
to second point. The third point defines the width of the roadway
from curb to curb in one direction of traffic flow.

**Illuminance -** Illuminance is a measure of the lumens incident on the pavement divided by the area. The units are lumens per square foot (footcandles) or lumens per square meter (lux). Illuminance is not impacted by the pavement's surface type or the angle of
observation.

Veiling Luminance (L_{v}) - A measure
of disability glare, veiling luminance is a luminance superimposed over
the eye's retinal image that is produced by stray light within the eye. In the
IES method, L_{v} is computed at the same points as the pavement luminance
with the observer 83.07 meters back from each computation point. Observer
line of sight is 1 degree below horizontal at 1.45 m above the road surface.

Veiling Luminance ratio - The
IES method uses the maximum value of Veiling Luminance (L_{v,max}) divided by
the Average Pavement Luminance (L_{avg}) as a measure of the disability glare
produced by a lighting system.

A**verage
Pavement Luminance** - The overall average luminance of the road
surface as observed from a specific point in cd/m_{2}. Metric units are
used, regardless of current settings. By default, observer position is
1/4 roadway width inset from the curb, 1.5 m above the pavement surface
and 60m back from the first lateral row of computation points in the grid. Line of sight is 0.5 - 1.5
degrees below horizontal, depending on the distance to the points. Observer position is static relative to the curb
line.

**Illuminance -** Illuminance is a measure of the lumens incident on the pavement divided by the area. The units are lumens per square meter (lux). Illuminance is not impacted by the pavement's surface type or the angle of
observation.

Longitudinal Uniformity - The ratio of minimum to maximum pavement luminance, illuminance or veiling luminance is taken along each longitudinal line of computation points. The worst-case ratio is displayed as the Longitudinal Uniformity Ratio. For the CIE method, an additional grid of pavement luminance points is computed, with observer position centered in the middle of each lane, 60m back from the first lateral row of computation points in the grid, and viewing along the line of points in that lane.

**Semi-cylindrical Illuminance -** Measured in lux, semi-cylindrical illuminance at a point could be considered a type of vertical illuminance, but its calculated value varies with the direction of interest. It is calculated at 1.5 meters above the road surface and on a half cylinder whose front is lined up parallel to the main directions of pedestrian movement, which for a road are usually longitudinal. The grid is located on the same points as the roadway luminance grid.

Surround Ratio - This is a ratio of the average horizontal illuminance on the two longitudinal strips each adjacent to the two edges of the carriageway (the surround illuminance), divided by the average horizontal illuminance on two longitudinal strips each adjacent to the two edges of the carriageway, but lying on the carriageway. The width of all four strips shall be the same, and equal to 5m, or half the width of the carriageway, or the width of the unobstructed strip lying off the carriageway, whichever is the least. For dual carriageways, both carriageways together are treated as a single carriageway unless they are separated by more than 10m.

Veiling Luminance (L_{v}) - A measure
of disability glare, Veiling Luminance is a luminance superimposed over
the eye's retinal image produced by stray light within the eye. In the
CIE method, L_{v} is computed along a single row of calculation points directly
in front of the observer position. By default, the distance of the observer to
the first lateral row of computation points in the grid is 2.75 x (mounting ht - 1.5) meters and 1/4 road width from the curb line. 0.5 - 1.5
degrees below horizontal, depending on the distance to the points.
The maximum value of L_{v} is used to compute the relative Threshold Increment
(TI). NOTE: The CIE 140-2000 method of calculating veiling luminance is *per 1000 lamp lumens*. This generates rather small values. Therefore, it is recommended that if you are calculating veiling luminance with the CIE standard, you first open the Units dialog (bottom toolbar in Model Mode or top toolbar in Roadway Optimizer) and set the Number of Decimals value to 2 or 3. This will help to avoid generating all zeros.

Relative Threshold Increment (TI) - A measure of the effect of disability glare produced by the lighting system. Threshold Increment is intended to yield the percentage increase in the luminance of the road's surface required to render an object just visible (threshold of visibility) under the proposed lighting system (glare present) as compared to the luminance required to render the object just visible in the absence of glare.

A**verage
Pavement Luminance** - The overall average luminance of the road
surface as observed from a specific point in cd/m_{2}. Metric units are
used, regardless of current settings. By default, observer position is
1/4 roadway width inset from the curb, 1.5 m above the pavement surface
and 60m back from the first lateral row of computation points in the grid. Line of sight is 0.5 - 1.5
degrees below horizontal, depending on the distance to the points. Observer position is static relative to the curb
line.

**Horizontal Illuminance -** Horizontal illuminance at a point is a measure of the lumens incident on the pavement divided by the area. The units are lumens per square meter (lux). Illuminance is not impacted by the pavement's surface type or the angle of
observation.

Longitudinal Uniformity - The ratio of minimum to maximum pavement luminance, illuminance or veiling luminance is taken along each longitudinal line of computation points. The worst-case ratio is displayed as the Longitudinal Uniformity Ratio. For the CIE method, an additional grid of pavement luminance points is computed, with observer position centered in the middle of each lane, 60m back from the first lateral row of computation points in the grid, and viewing along the line of points in that lane.

V**ertical Illuminance** - Measured in lux, vertical illuminance at a point is calculated on a plane 1.5 m above the surface of the road. The grid is located on the same points as the roadway luminance grid.

**Semi-cylindrical Illuminance -** Measured in lux, semi-cylindrical illuminance at a point could be considered a type of vertical illuminance, but its calculated value varies with the direction of interest. It is calculated at 1.5 meters above the road surface and on a half cylinder whose front is lined up parallel to the main directions of pedestrian movement, which for a road are usually longitudinal. The grid is located on the same points as the roadway luminance grid.

Hemispherical Illuminance - Measured in lux, hemispherical illuminance at a point is calculated at ground level on the road surface. Its formula is similar to the formula for horizontal illuminance, but differs from it in the way that the angle of incidence is considered.

Surround Ratio - This is a ratio of the average horizontal illuminance on the two longitudinal strips each adjacent to the two edges of the carriageway (the surround illuminance), divided by the average horizontal illuminance on two longitudinal strips each adjacent to the two edges of the carriageway, but lying on the carriageway. The width of all four strips shall be the same, and equal to 5m, or half the width of the carriageway, or the width of the unobstructed strip lying off the carriageway, whichever is the least. For dual carriageways, both carriageways together are treated as a single carriageway unless they are separated by more than 10m.

Veiling Luminance (L_{v}) - A measure
of disability glare, Veiling Luminance is a luminance superimposed over
the eye's retinal image produced by stray light within the eye. In the
BSEN method, L_{v} is computed along a single row of calculation points directly
in front of the observer position. By default, the distance of the observer to
the first lateral row of computation points in the grid is 2.75 x (mounting ht - 1.5) meters and 1/4 road width from the curb line. 0.5 - 1.5
degrees below horizontal, depending on the distance to the points.
The maximum value of L_{v} is used to compute the relative Threshold Increment
(TI).

Relative Threshold Increment (TI) - A measure of the effect of disability glare produced by the lighting system. Threshold Increment is intended to yield the percentage increase in the luminance of the road's surface required to render an object just visible (threshold of visibility) under the proposed lighting system (glare present) as compared to the luminance required to render the object just visible in the absence of glare.

A**verage
Pavement Luminance** - The overall average luminance of the road
surface as observed from a specific point in cd/m_{2}. Metric units are
used, regardless of current settings. By default, observer position is
1/4 roadway width inset from the curb, 1.5 m above the pavement surface
and 60m back from the first lateral row of computation points in the grid. Line of sight is 0.5 - 1.5
degrees below horizontal, depending on the distance to the points. Observer position is static relative to the curb
line.

**Illuminance -** Illuminance is a measure of the lumens incident on the pavement divided by the area. The units are lumens per square meter (lux). Illuminance is not impacted by the pavement's surface type or the angle of
observation.

Longitudinal Uniformity - The ratio of minimum to maximum pavement luminance, illuminance or veiling luminance is taken along each longitudinal line of computation points. The worst-case ratio is displayed as the Longitudinal Uniformity Ratio. For the CIE method, an additional grid of pavement luminance points is computed, with observer position centered in the middle of each lane, 60m back from the first lateral row of computation points in the grid, and viewing along the line of points in that lane.

**Semi-cylindrical Illuminance -** Measured in lux, semi-cylindrical illuminance at a point could be considered a type of vertical illuminance, but its calculated value varies with the direction of interest. It is calculated at 1.5 meters above the road surface and on a half cylinder whose front is lined up parallel to the main directions of pedestrian movement, which for a road are usually longitudinal. The grid is located on the same points as the roadway luminance grid.

Surround Ratio - This is a ratio of the average horizontal illuminance on the two longitudinal strips each adjacent to the two edges of the carriageway (the surround illuminance), divided by the average horizontal illuminance on two longitudinal strips each adjacent to the two edges of the carriageway, but lying on the carriageway. The width of all four strips shall be the same, and equal to 5m, or half the width of the carriageway, or the width of the unobstructed strip lying off the carriageway, whichever is the least. For dual carriageways, both carriageways together are treated as a single carriageway unless they are separated by more than 10m.

Veiling Luminance (L_{v}) - A measure
of disability glare, Veiling Luminance is a luminance superimposed over
the eye's retinal image produced by stray light within the eye. In the
CIE method, L_{v} is computed along a single row of calculation points directly
in front of the observer position. By default, the distance of the observer to
the first lateral row of computation points in the grid is 2.75 x (mounting ht - 1.5) meters and 1/4 road width from the curb line. 0.5 - 1.5
degrees below horizontal, depending on the distance to the points.
The maximum value of L_{v} is used to compute the relative Threshold Increment
(TI). NOTE: The NBR5101-2012 method of calculating veiling luminance is *per 1000 lamp lumens*. This generates rather small values. Therefore, it is recommended that if you are calculating veiling luminance with the CIE standard, you first open the Units dialog (bottom toolbar in Model Mode or top toolbar in Roadway Optimizer) and set the Number of Decimals value to 2 or 3. This will help to avoid generating all zeros.

Relative Threshold Increment (TI) - A measure of the effect of disability glare produced by the lighting system. Threshold Increment is intended to yield the percentage increase in the luminance of the road's surface required to render an object just visible (threshold of visibility) under the proposed lighting system (glare present) as compared to the luminance required to render the object just visible in the absence of glare.

Australia Standard 1158.2- 2005

A**verage
Pavement Luminance** - The overall average luminance of the road
surface as observed from a specific point in cd/m_{2}. Metric units are
used, regardless of current settings. By default, observer position is
1/2 roadway width inset from the curb, 1.5 m above the pavement surface
and 60m back from the first lateral row of computation points in the grid. Line of sight is 0.5 - 1.5
degrees below horizontal, depending on the distance to the points. Observer position is static relative to the curb
line.

**Illuminance -** Illuminance is a measure of the lumens incident on the pavement divided by the area. The units are lumens per square meter (lux). Illuminance is not impacted by the pavement's surface type or the angle of
observation.

Surround Ratio - This is a ratio of the average horizontal illuminance on the two longitudinal strips each adjacent to the two edges of the carriageway (the surround illuminance), divided by the average horizontal illuminance on two longitudinal strips each adjacent to the two edges of the carriageway, but lying on the carriageway. The width of all four strips shall be the same, and equal to 3 meters. The grid shall be placed at the same distance as the luminance calculation field.

Veiling Luminance (L_{v}) - A measure
of disability glare, Veiling Luminance is a luminance superimposed over
the eye's retinal image produced by stray light within the eye. In the AS method, L_{v} is computed at the same points as the pavement luminance with the observer 60 meters back from the computation point. Observer line of sight is 0.5 - 1.5
degrees below horizontal, depending on the distance to the points.
The maximum value of L_{v} is used to compute the relative Threshold Increment
(TI).

**Vertical Illuminance (E _{pv}) - **Calculated on a series of parallel vertical planes, at a height of 1.5m above the locations of the horizontal illuminance points. The plane shall be orientated to be transverse to the pathway.

Australia Standard 1158.2- 2005 - SAASTAN

The SAASTAN software calculates some of the Australian metrics differently than Australian Standard 1158.2-2005 defines. Specifically, the luminaire cycles that will contribute to the calculation grid points are different in SAASTAN from what is defined in AS 1158.2-2005, and the position of the observer for the veiling luminance calculations is also different. These differences can lead to different calculated values for any or all of the roadway metrics.

AGi32 includes AS 1158.2-2005 - SAASTAN as a selectable "standard" for those projects that must be calculated by SAASTAN methods rather than by Standard 1158.2-2005.

New Zealand Standard 1158.2- 2005

A**verage
Pavement Luminance** - The overall average luminance of the road
surface as observed from a specific point in cd/m_{2}. Metric units are
used, regardless of current settings. By default, observer position is
1/2 lane width inset from the curb, 1.5 m above the pavement surface
and 60m back from the first lateral row of computation points in the grid. Line of sight is 0.5 - 1.5
degrees below horizontal, depending on the distance to the points. Observer position is static relative to the curb
line.

**Illuminance -** Illuminance is a measure of the lumens incident on the pavement divided by the area. The units are lumens per square meter (lux). Illuminance is not impacted by the pavement's surface type or the angle of
observation.

Surround Ratio - This is a ratio of the average horizontal illuminance on the two longitudinal strips each adjacent to the two edges of the carriageway (the surround illuminance), divided by the average horizontal illuminance on two longitudinal strips each adjacent to the two edges of the carriageway, but lying on the carriageway. The width of all four strips shall be the same, and equal to 3 meters.The grid shall be placed at the same distance as the luminance calculation field.

Veiling Luminance (L_{v}) - A measure
of disability glare, Veiling Luminance is a luminance superimposed over
the eye's retinal image produced by stray light within the eye. In the NZ method, L_{v} is computed at the same points as the pavement luminance with the observer 60 meters back from the computation point. Observer line of sight is 0.5 - 1.5
degrees below horizontal, depending on the distance to the points.
The maximum value of L_{v} is used to compute the relative Threshold Increment
(TI).

**Vertical Illuminance (E _{pv}) - **Calculated on a series of parallel vertical planes, at a height of 1.5m above the locations of the horizontal illuminance points. The plane shall be orientated to be transverse to the pathway.