Technical Summary of Research into
Unit Power Density and Unit Uplight Density:
Calculations

Table of Contents

Calculations: Different Phases

Calculations were made for every photometric file in every appropriate roadway configuration and design criteria for each phase. In the preliminary phase, the calculations were only for the "base case" of meeting both the illuminance and luminance criteria together. This "base case" for design criteria is used throughout the research, with most comparisons being made relative to that case. As shown in the results, this "base case" does represent a more stringent set of design criteria than either illuminance or luminance alone. In the intermediate phase, all the appropriate combinations of the expanded photometric set and roadway & wattage matrix were all calculated for the "base case".

For the preliminary phase, 6,887 calculations were recorded, for each step from the initial "assumed" system to the final possibility at the limit for the mounting height (and with the luminaire located at the edge of the roadway, as discussed above.) This allowed for inspection of the optimization routine as the calculation proceeded along the path to optimization for mounting height. The results were evaluated and used for the further development of the optimization routine, as discussed above. The conclusion from this portion of the research [3] was that the optimization routine did work properly for the illuminance and luminance criteria (but not for the Small Target Visibility (STV) [1] criteria.)

For the intermediate and advanced phases, only the optimized systems were recorded. Over these phases, the combinations of design criteria and constraints were applied to some subsets of the photometric files and roadway configurations. These additional constraints are discussed in detail below.

The numbers of files, groups and runs calculated for the UPD calculations in the combined intermediate and advanced phases are shown in Table 7. The reduced number used for the UUD calculations are shown in Table 8. In those tables "#G" shows the number of groups - such as "C10s150H" - for that combination of lamp, wattage, criteria and constraints. For most groups, all appropriate photometric files were calculated, but in some only a subset were included (and the details are discussed below.) For these situations in Tables 7 and 8, after the number of groups there are numbers in parentheses, showing the number of photometric files in the subset that was calculated for each group in that combination. The standard (MH) and pulse start (MHP) calculations are shown separately, although as discussed above they differ only by the rated lumens values used and so could be considered one more variation.

As shown in Tables 7 and 8, the overall range of this research is wide and a number of individual situations were investigated. When comparisons are made, typically the "Base Case" is used and so that condition has the most complete set of calculations, including all of the roadway and wattage combinations shown in Table 6. For other situations - discussed in detail below - fewer combinations are included because completing the set of possible calculations is unnecessary, since the trends are evident within the reduced range, or the constraints are impractical. The "HPS LLF" calculations only included roadways with an odd number of lanes for Major, Collector and Local classifications. The calculations with the "Overhang" constraint only include roadway up to four lanes wide. The calculations using illuminance criteria were only made for 250W sources. Details about which combinations of roadways and sources were included in the calculations for which set of criteria and/or constraints can be found in Tables 10 and 11 below.

Calculations: Illuminance and Luminance

The calculations for luminance and illuminance differ from the "base case" by requiring that only one design method's criteria from RP-8-00 be met. For Illuminance, the criteria are average, uniformity ratio of average-to-minimum and veiling luminance. For Luminance, the criteria are average, uniformity as maximum-to-minimum and average-to-minimum and veiling luminance. Therefore every calculation meets criteria for the quantity of illumination, the uniformity of illumination and the allowable glare. The intent is to evaluate which design method allows for better system performance. This is part of the intermediate phase that was extended further during the advanced phase.

Calculations: Zero Overhang

The calculations for "zero overhang" were made with the system constrained to keep the luminaire at or set back from the edge of the roadway. This was achieved by resetting the range of overhang values in the parameters file for the optimization calculations for the group. The intent is to see if requiring that the luminaires have zero overhang makes a significant difference in the system performance, and in which photometric distributions perform best. This is part of the advanced phase.

Calculations: HPS LLF

The LLF for the HPS systems in this set of runs was changed from 0.70 to 0.50, a decrease of around 28% for the overall system. The change is described as a 40% increase [5] to allow for comparison with the changes made by the increase in rated lamp lumens for the MH systems using MHP lamps. The calculations for the adjusted Light Loss Factors with HPS systems were made for all the photometric files but only for roadway configurations with an odd number of lanes - one lane Local, one and three lane Collector, one, three and five lane Major. These calculation investigate two related aspects of the overall research. First is the change in overall performance compared to the scaled increase in "available lumens" and second is the confirmation that this LLF change works "equivalently" the change in lamp lumens works for the MH and MHP systems. This is not to say that the relative change is the same because the sizes of the changes are different - the rated lumens for the MHP are increases of 5% to 30%. What is of interest is confirmation that the size of the change in system performance is relative to the size of the change in the "available lumens" - regardless of whether that change is for MH or HPS, and whether it is applied through the LLF or lamp lumens. This is part of the advanced phase.

Calculations: Major High

The calculations for the Major High roadways were made with all the 250 and 400 Watt MHP and HPS photometry, for roadways from two to six lanes wide and meeting the "base case" design criteria. This changes only the average illuminance and luminance criteria, while the uniformity and veiling luminance criteria remain the same. The intent is to evaluate the increase in UPD (and installed lumens) as the illumination increases. This is part of the advanced phase.

Calculations: UPD and UUD

For each optimized system the corresponding UPD was calculated as described above. For each optimized system using luminaires with complete photometry, the corresponding UUD was calculated as described above.

Calculations: Groups, "Top 5" and "Top 10"

The specific combinations of roadway class, width, design method, design criteria, lamp type, and lamp wattage, along with specific restrictions or changes, were identified as a group.

Groups were identified by composite names, starting with the roadway class (M, C or L) followed by the total width (e.g. 07 for two lanes) followed by the criteria identifier followed by a tag for wattage (e.g. 40 for 400) and finished by a letter for the lamp type (H for HPS, M for MH and P for MH pulse start). A typical string - shown "mostly" in Table 9's header - is "C07s150H" for a collector roadway of 7 m width, meeting the standard (base case) criteria set for such a roadway using 150 lamps of HPS. The header in Table 9 has no "H" because this data is from the preliminary phase and only HPS lamps were used.

Each group was sorted by UPD, and the value associated with the fifth lowest UPD for the group was established as the criterion for that group's "Top 5". This procedure was repeated including only those photometric files with full cutoff distributions, to establish a group's "Top 5" UPD criterion for "full-cutoff only". All appropriate files in each group with UPD less than or equal to the "Top 5" criterion were averaged to produce the "averaged over the Top 5" UPD value for the group, separately for "any distribution allowed" and for "full cutoff only" (e.g. in Tables 10 and 11). Since different photometric files may produce optimized systems with the same UPD value, any group's "Top 5" may include more than five files. This procedure insures that at least five different photometric files are included in the group's "averaged over the Top 5" UPD value. Because of the possibility that systems have the same UPD value, there may be more than five systems that meet the "Top 5" criterion for a group.

"Top 10" values were also established for every group, using the tenth lowest UPD value in the entire group. Because of the possibility that systems have the same UPD value, there may be more than ten systems that meet the "Top 10" criterion for a group.

This approach is introduced in the intermediate phase and applied throughout the advanced phase.