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For procedure One, the luminaire is assumed to be located over the edge of the traveled way. Only the mounting height is varied to find the maximum luminaire cycle distance for luminaires located on the edge of the traveled way.
For procedure Two, the overhang/setback of the luminaire is varied as well as the mounting height, to find the maximum luminaire cycle distance.
Both procedures are optimizing a single combination of luminaire and roadway. This means that the photometric distribution, rated lumens, light loss factor and luminaire orientation are constant during the optimization procedure. The roadway characteristics of the number of lanes, width of each lane and the surface classification are kept constant through the optimization. Finally, the design criteria which correspond to the roadway classification are constant during the optimization.
Both procedures use a software routine which calculates the performance of a roadway lighting design according to [1] and compares the results to the relevant criteria from [1] to determine if the design meets the requirements. This single-calculation-and-comparison routine is called reiteratively by a routine which compares the results of the most recent single-calculation-and-comparison to earlier results and then either branches the program flow or makes changes to the system geometry in preset steps and proceeds with the next iteration.
For procedure One, the reiteration starts with a low value (specified by the input file) for the mounting height and it calculates a corresponding short distance for the luminaire cycle distance. The single-calculation-and-comparison routine is called and the design calculations performed and returned. If this initial design does not meet the criteria, either the mounting height or luminaire cycle distance is increased and the procedure continues. Otherwise the process repeats with increasing luminaire cycle distance values, until the maximum-for-that-mounting-height is determined. This occurs when the results for the design with the next longer luminaire cycle distance do not meet the design criteria. The luminaire cycle distance that is the last-that-meets-the-criteria is also the maximum-for-that-mounting-height.
The mounting height is increased by one step and the process is repeated to determine the corresponding maximum-for-that-mounting-height. The two maximums are compared, and if the maximum-for-the-higher-height is equal to or greater than the maximum-for-the-lower-height, the routine continues with the next higher mounting height. Otherwise, the maximum-for-the-lower-height is the maximum for the combination of roadway and luminaire, so the routine records the design details in a file as the optimum.
The extension to procedure Two uses all of procedure One inside a reiterative routine which adjusts the overhang/setback and compares the maximum luminaire cycle distance found for each overhang/setback to the others to direct the calculations. The overhang/setback is the value corresponding to the horizontal distance perpendicular to the direction of travel between the edge of the traveled way and the luminaire position. Overhang/setback is positive when the luminaire is located over the traveled way and negative when the luminaire is located away from the traveled way.
The initial mounting height is set in the optimization input file. For 150W or 175W luminaires, the initial mounting heights were set to 5 meters. For 250W and for 400W luminaires, the initial mounting heights were 6 meters. The increment for the mounting height is 0.5 meters throughout. The final mounting heights were 15 or 18 meters.
The initial luminaire cycle distance is calculated after each mounting height is set, as the distance equal to or less than two mounting heights and equal to an integer multiple of the step specified for the luminaire cycle distance. The increment for the luminaire cycle distance is 2 meters for the staggered layouts used throughout this research. The final luminaire cycle distance was recorded as the optimum for that combination of luminaire and roadway.
The design criteria to be met are from [1] and shown in Table 1. The calculations use both the illuminance and the luminance criteria for the "base case" of these calculations, and each set of criteria separately for the "illuminance" case or the "luminance" case, as discussed below.
Table 1: Criteria from ANSI/IESNA RP-8-00Classifications Eavg Eavg / Lavg Lavg / Lmax / Lveil/ Roadway Area R1 R2 & R3 R4 Emin Lmin Lmin Lavg Major High 12.0 17.0 15.0 3.0 1.2 3.0 5.0 0.3 Major Med 9.0 13.0 11.0 3.0 0.9 3.0 5.0 0.3 Collector Med 6.0 9.0 8.0 4.0 0.6 3.5 6.0 0.4 Local Med 5.0 7.0 6.0 6.0 0.5 6.0 10.0 0.4 Notes: - The units of Eavg are lux, the units of Lavg are cd/m2. - For the Illuminance method, the Eavg value (appropriate to the roadway surface), the Eavg/Emin ratio and the Lveil/Lavg ratio, comprise the set of criteria. - For the Luminance method, the Lavg value, the Lavg/Lmin ratio, the Lmax/Lmin ratio and the Lveil/Lavg ratio, comprise the set of criteria.
As discussed in the notes to Table 1, the criteria for each method must be met as a set - all the relevant criteria must be met for the design to meet the criteria. Therefore these are average magnitude, uniformity and veiling luminance requirements for every system considered in this work.
Two different sources each have three different wattages included in this work. The sources are High Pressure Sodium (HPS) and Metal Halide Pulse-start (MHP). The three wattages correspond to small, medium and large: 150W for HPS and 175W for MHP; 250W; 400W. The photometric distributions were all applied using standard values for the rated lamp lumens [7,8] and the Light Loss Factor (LLFmaint). In addition, the UPD values were calculated using standardized wattage values. Table 2 shows the values used throughout these calculations.
Table 2: Luminaire and Lamp DataSource Wattage Rated Lumens Luminaire Input Watts LLFmaint LLFavg HPS 150 16,000 166 0.70 0.85 250 27,500 295 0.70 0.85 400 50,000 460 0.70 0.85 MHP 175 17,500 210 0.50 0.75 250 21,500 295 0.50 0.75 400 44,000 455 0.50 0.75
The photometric files used in this research are a (still-growing) collection of files provided by many sources. Each file is made anonymous, analyzed and classified according to the IESNA distribution and cutoff definitions for roadway luminaires [1]. The set of files used for the preliminary phase of the research was increased for the intermediate and advanced phases, and a few files were dropped when they did not work properly with the optimization procedures (typically these files represented "poor performers" in the situations where they did work properly.) Some near-duplication exists, because files with and without house side shields may be effectively the same on the roadway side, but must both be included in the set of files because only such testing can confirm that they are effectively the same.
The photometric files were grouped by lamp wattage. A standard value was used for the "rated lumens" of each file (along with scaling automatically applied as necessary in the calculations) as discussed above and shown in Table 2.
The files were also grouped by IESNA cutoff classification [1], which includes full cutoff (FC), cutoff (CO), semi-cutoff (SC) and non-cutoff (NC).
For the preliminary phase, 73 photometric files were included, all HPS, in three different wattages and three different cutoff classifications. Because there were no non-cutoff files for some wattages, all non-cutoff files were excluded for this phase. The distribution of the files is shown in Table 3.
Table 3: Photometric Files, PreliminaryLamp Wattage Total FC CO SC HPS 150 18 2 7 9 250 17 5 6 6 400 38 8 16 14
For the intermediate and advanced phases, a total of 387 photometric files were included, 153 MH and 234 HPS, in three different wattages and including all four different cutoff classifications. The distribution of the files is shown in Table 4.
Table 4: Photometric Files, Intermediate and AdvancedLamp Wattage Total FC CO SC NC HPS 150 67 17 20 14 16 250 70 30 19 14 7 400 97 28 36 21 12 MH 175 59 25 6 13 15 250 47 27 4 9 7 400 47 20 16 4 7
The photometric files were also evaluated for completeness, because some files did not have complete intensity data for the upper hemisphere. These files had to be excluded from uplight calculations. The reduced set of files used for the uplight calculations is shown in Table 5.
Table 5: Photometric Files for Uplight Calculations, Intermediate and AdvancedLamp Wattage Total FC CO SC NC HPS 150 45 17 11 7 10 250 44 30 8 6 0 400 55 28 20 7 0 MH 175 50 25 6 10 9 250 30 27 2 1 0 400 33 20 7 4 2
In the advanced phase, the MH files were used with rated lumens for pulse start lamps, as described above, but no other changes were made.
The photometric files were applied to standard roadways which represent most of the full range of roadway criteria [1]. For the typical roadways investigated in this work, the roadway classification varies from local to collector to major, while the area classification is typically "medium", except for a few runs made with the "major high" combination to investigate the relative change in UPD values [5]. Theses combinations are discussed in detail below.
The photometric files were applied to standard roadways of varying widths, associated with the classifications and representing a full range of sizes. Each roadway width consists of the traveled way and does not include shoulders.
The roadway widths used in this work relate to the number of lanes, with between 3.5 and 4 meters as the width of each lane, depending on how it comes out to make an even total width for the roadway. For a given roadway, every lane is the same width, so the four lanes in a 13 m wide roadway are each 3.75 m wide. The summary of roadway width and number of lanes is shown in the first two columns of Table 6 below.
The combinations of roadway classification and width were combined again with the lamp wattages as shown in Table 6 below. The lower wattage lamps were used for local and collector roadways up to two or three lanes wide, while the higher wattage lamps were used for the collector and major roadway for all widths up to six lanes. The 250W lamps were used with all combinations.
Some combinations shown in Table 6 were not included in the preliminary phase and were added for the intermediate and advanced phases, and these combinations are shown in italics in Table 5.
Table 6: Roadway and Lamp Wattage MatrixRoadway Class Local Collector Major Widths (m) Lanes 4 1 150/175 & 250 150/175, 250 & 400 250 & 400 7 2 150/175 & 250 150/175, 250 & 400 250 & 400 10 3 150/175, 250 & 400 250 & 400 13 4 250 & 400 17 5 250 & 400 20 6 250 & 400
The roadways considered in this work all have R3 surfaces as defined in [1]. The Q0 is left at the default of 0.07 throughout.
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