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Field evaluation of selected light sources for roadway lighting
j o u r n a l o f t r a f fi c a n d t r a n s p o r t a t i o n e n g i n e e r i n g ( e n g l i s h e d i t i o n ) 2 0 1 8 ; 5 ( 5 ) : 3 7 2 e3 8 5
Available online at www.sciencedirect.com
ScienceDirect journal homepage: www.elsevier.com/locate/jtte
Original Research Paper
Field evaluation of selected light sources for roadway lighting Yi Jiang a,*, Shuo Li b, Bowen Guan c, Guangyuan Zhao a, Dave Boruff d, Lalit Garg d, Prakash Patel d a
Department of Building Construction Management, Purdue University, West Lafayette, IN 47907, USA Division of Research and Development, Indiana Department of Transportation, West Lafayette, IN 47906, USA c School of Materials Science and Engineering, Chang'an University, Xi'an 710064, China d Indiana Department of Transportation, Indianapolis, IN 46204, USA b
highlights The illuminance values of various types of devices were measured under actual roadway lighting conditions. The performances of the luminaires were evaluated and compared to the conventional HPS luminaires in both roadside lighting and high mast lighting. LED lighting technologies were recommended for roadway lighting applications. It was recommended that further efforts be made by manufacturers to improve the light uniformity.
article info
abstract
Article history:
The development of new lighting sources, such as light emitting diode (LED), induction,
Received 18 February 2018
and plasma, presented more possible cost effective ways for roadway lighting. A study was
Received in revised form
therefore conducted for the Indiana Department of Transportation (INDOT) to evaluate the
20 May 2018
performance and effectiveness of some selected new lighting devices in roadway lighting.
Accepted 23 May 2018
This paper describes the field evaluation process and presents the evaluation results. A
Available online 6 August 2018
number of LEDs, plasma and induction luminaires from various manufacturers were selected to replace the existing high pressure sodium (HPS) lamps in conventional and high
Keywords:
mast lightings. Illuminance values were measured over a period of 12 months on the
Roadway lighting
existing and new light sources. Light performance metrics, including illuminance level and
Luminaires
uniformity ratios, were calculated to make quantitative comparisons of the HPS and new
Illuminance
types of light devices. Based on the evaluation in terms of lighting performance and life
Field tests
cycle costs, it was concluded that LED luminaires should be utilized in roadway lighting in
LED
place of HPS luminaires. The results of this study will be useful to state highway and city
HPS
street agencies in making decisions on their lighting policies and developing technical specifications for use of the new lighting technologies in roadway and street lightings. The study provides a basis for manufacturers to improve their luminaire design and integration to better fit the needs of roadway and street lightings.
* Corresponding author. Tel.: þ1 765 409 0670. E-mail addresses: [email protected] (Y. Jiang), [email protected] (S. Li), [email protected] (B. Guan), [email protected] (G. Zhao), [email protected] (D. Boruff), [email protected] (L. Garg), [email protected] (P. Patel). Peer review under responsibility of Periodical Offices of Chang'an University. https://doi.org/10.1016/j.jtte.2018.05.002 2095-7564/© 2018 Periodical Offices of Chang'an University. Publishing services by Elsevier B.V. on behalf of Owner. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
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373
© 2018 Periodical Offices of Chang'an University. Publishing services by Elsevier B.V. on behalf of Owner. This is an open access article under the CC BY-NC-ND license (http:// creativecommons.org/licenses/by-nc-nd/4.0/).
1.
Introduction
There is an increasing interest in using new lighting technologies in roadway and street lightings. The new lighting technologies include light emitting diode (LED), induction and plasma light sources. The most commonly claimed benefits of the new light sources include increased reliability, improved efficiency, and reduced maintenance costs. Due to this growing interest and demand, an NCHRP study (Bullough et al., 2013) was conducted to evaluate the potential and proper application of LED lighting technology. They concluded that efficiency and photometric performance had evolved to the point that LED roadway lighting was a feasible choice and could often lead to reductions in energy use of around 15% or greater, or life-cycle cost reductions in the long term, depending upon the initial cost of LED luminaires. However, specific luminaires using LED sources can have a wide range of performance, and should be judged on an individual luminaire basis. The Indiana Department of Transportation (INDOT) has been contacted by vendors requesting possible application of the new light sources for roadway lighting. Before adopting the new lighting systems, INDOT would like to determine if the new lighting systems meet required light output and if they are cost effective. Moreover, it is necessary for INDOT to establish standardized guidelines for evaluating the new lighting systems prior to the formal adoption. This study was conducted to evaluate some selected lighting devices in roadway lighting. The major effort of this study was to address engineering issues, such as light levels, life cycle cost, maintenance, traffic safety, and approval procedures for new lighting technologies based on field evaluations. The evaluations include the properties, benefits and costs, and effectiveness of selected new lighting devices in roadway lighting applications. Illuminance values were measured over a period of 12 months on the existing and new light sources to identify light distributions. Light performance metrics in terms of illuminance levels and uniformity ratios were calculated to make quantitative comparisons between the lighting performances of the existing and new lighting devices. It is believed that the information presented in this paper will be useful to state highway and city street agencies in making decisions on their lighting policies and developing technical specifications for use of the new lighting technologies in roadway and street lightings. It is also believed that such information is useful for manufacturers to improve their luminaire model design and integration to better fit the needs of roadway and street lightings.
2.
Highway lighting luminaires
2.1.
HPS lamps
There are three types of lighting sources that have been widely used for indoor and outdoor lighting applications, including incandescent, fluorescent, and high intensity discharge (HID) lights. For highway facilities, lighting is commonly provided at interchanges, rest areas, weight stations, tunnels, and parking lots. The HID light source family consists mainly of four members, including mercury vapor (MV), low-pressure sodium (LPS), high pressure sodium (HPS), and metal halide (MH) lights. HPS is the most commonly used for roadway lighting. HPS luminaires are the main lighting source for almost all state-owned highways in Indiana (INDOT, 2012). HPS lamps were introduced in the 1960s. An HPS lamp commonly consists of four basic components, including a sealed, translucent, ceramic arc tube, main electrodes, an outer bulb, and a base (Halonen et al., 2010; USDOE, 2010). The arc tube ceramic contains a mixture of a small amount of xenon gas and sodium-mercury amalgam and is used to provide a proper environment for producing light. The xenon at a low pressure is used as a “starter gas” in the HPS lamp. Lying at the coolest part of the lamp, the sodiummercury amalgam provides the sodium-mercury vapor that is needed to draw an arc. The main electrodes are made of tungsten and carry a high-voltage, high-frequency pulse to strike the arc and vaporize the mercury and sodium. The outer bulb, typically elliptical in shape and made of hard glass, protects the arc tube from damage and prevents oxidation of the internal parts. It also contains a vacuum that reduces convection and heat losses from the arc tube to maintain high efficacy. The lamp base is typically a screwed base made of brass or nickel and provides a socket for electrical connection. An HPS lamp requires an inductive ballast to regulate the arc current flow and deliver the proper voltage to the arc.
2.2.
MH lamps
MH lamps are also a member of HID lamp family. MH lamps can offer an excellent combination of quality and performance. MH lamps not only present more natural blue-white light compared to HPS lamps, but also provide increased efficacy compared to MV lamps. A standard MH lamp consists of four basic components, including quartz arc tube, main electrodes, outer bulb, and base. The operation of metal halide lamps is similar to HPS lamps in that they produce light by way of an arc tube contained within a glass bulb (LSC, 2017). When an MH lamp is energized, the
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Fig. 1 e Map of light test site.
electric current passes through the arc tube and ignites an electric arc through a gaseous mixture of vaporized mercury and metal halides, which are compounds of metals with bromine or iodine. Similar to HPS lamps, inductive ballast is used to regulate the current and the voltage to the lamp.
2.3.
LED lighting
LED lighting is a type of solid-state lighting. It is a semiconductor based device that produces light when an electrical current passes through it. Multiple LEDs can be combined into LED arrays. LED lamp, as defined by IES (2008), is an LED device with an integrated driver and a standardized base that is designed to connect to the branch circuit via a standardized lamp holder/socket. An LED is a two-lead semiconductor light source. It is a pen junction diode that emits light when activated (HMC,
2005). When a suitable voltage is applied to the leads, electrons are able to recombine with electron holes within the device, releasing energy in the form of photons. LEDs are typically small (less than 1 mm2) and integrated optical components may be used to shape the radiation pattern (Moreno and Sun, 2008). A basic LED luminaire consists of optical, electrical, mechanical, and thermal components (Halonen et al., 2010; Philips, 2017). When an electron meets a hole, the electron falls into a lower energy state and releases a particle known as a photon, which is where the visible light comes from. A heat sink is needed to draw the heat away from the LED array. The heat sink is typically integrated into the outer housing of the fixture to maximize heat dissipation. With the advancements in optics and semi-conducting technologies, LED technologies have become more reliable, and the prices of LED luminaires have continuously declined. As a result, LED lighting applications have become more financially attainable.
Table 1 e Geometric dimensions of lighting poles. Test zone
1
2
3
4
5
Pole#
1 2 3 4 6 7 8 9 10 14 15 16 T-2
EMH (ft)
42
42
42
42
125
Pole spacing
MAL (ft)
Pole setback (ft)
Design
Measured
Design
Measured
Design
e 275 280 e 300 280 e 290 290 e 270 270 N.A.
e 273 277 e 340 280 e 289 287 e 270 274 N.A.
15
18
20
15
16
15
15
15
18
e
e
Measured
20.0 19.5 20.6 20 8.7 20.4 21.0 20 20.4 22.4 20.6 20 23.5 20 24.3 15 21.1 225 (offset from US 231)
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2.4.
Plasma lighting
3.
Plasma, also known as lighting emitting Plasma (LEP), is an ionized gas with equal number of positive and negative charges. Plasma lamps are electrodeless lamps, meaning there are no electrical connections inside of the bulb, which use radio frequency (RF) waves to excite Plasma within the bulb. A plasma lamp is usually a clear glass sphere filled with a mixture of various gases, such as neon, argon, xenon and krypton, at nearly atmospheric pressure. They are driven by high-frequency alternating current. The drive circuit is essentially a specialized power inverter. The radio-frequency energy from the transformer is transmitted into the gas within the globe through an electrode at its center. The radiofrequency energy is admitted into the larger space by capacitive coupling right through the glass. Plasma filaments extend from the inner electrode to the outer glass insulator, giving the appearance of moving tendrils of colored light within the volume of the globe (Plasma globe, 2018).
2.5.
Induction lighting
Induction lamps are another form of an electrode-less lamp. An induction lamp consists of three major components, including ballast (known as HF generator), power coupler, and lamp bulb (ETC, 2017). The ballast contains an oscillator and preconditioning and filtering circuits. It first converts AC to DC, and then DC to AC. The power coupler contains an antenna which is made of a primary induction coil and ferrite core. It transfers energy from the ballast to the discharge inside the lamp bulb. The lamp bulb is a sealed glass bulb containing a low pressure inert gas with a small amount of mercury vapor. When an induction lamp is powered, the ballast generates HF current. The HF current is sent through the electromagnet and a strong magnetic field is produced. The energy is transferred from the magnet to the mercury in the tube via the antenna and excites the mercury atoms. The mercury vapor emits ultraviolet light which is changed into visible light by the phosphor coating on the inside of the glass.
Test site and selected luminaires
The test site was located near the interchange of I-74 and US231 in the vicinity of Crawfordsville, Indiana, as shown in Fig. 1. The site was selected in the consideration of easy luminaire installation, illuminance measurement, and traffic control set up. The site was divided into five test zones to expedite the evaluation process during the study period. Lightings in zones 1 to 4 were all road-side lightings with single-sided layout. The lighting in zone 5 was a high mast lighting. Zone 1 was located on US-231 northbound, consisting of three lighting poles, denoted as poles 1, 2 and 3 (two luminaire cycles). The road segment consisted of two through lanes and one turning lane. Zones 2 and 3 were located on US-231 southbound, each consisting of three lighting poles, denoted as poles 4, 6 and 7 in zone 2, and poles 8, 9 and 10 in zone 3. The road segments in zones 2 and 3 consisted of one through lane and one turning lane. Zone 4 was located on I-74 westbound, consisting of poles 14, 15 and 16. The road segment had two through lanes and one merging lane. Zone 5 was the upper quadrant of the interchange with a single high mast lighting pole, i.e., T-2, covering a 2-way ramp, part of interchange and a signalized, 3-leg intersection of US-231 and the ramp. Presented in Table 1 are the layouts and geomertic dimensions of the current lighting poles in these five test zones. Field visits were conducted to verify the design dimensions of the light poles. It was found that most measured dimensions agree well with the design dimensions, except for the pole spacing between poles 4 and 6. The effective mounting height (EMH) is 42 feet for all road-side lighting poles and 125 feet for the HM lighting pole. Discrepancies were observed between the design mast arm length (MAL) and measured MAL as well as between the measured pole setback and the design pole setback. The INDOT records indicated that the light poles were installed in 1993 in this test site. A total of ten types of luminaire were selected by the INDOT engineers according to the product availabilities and the vendor/manufacturer recommendations. Table 2 presents
Table 2 e Information on selected luminaries. Type 250 W, HPS 400 W, HPS 1000 W, HPS 320 W, MH 258 W, LED 270 W, LED 200 W, LED 392 W, LED 295 W, plasma 200 W, induction
Manufacturer model
Initial lumens
Lamp efficacy
GE LU250 GE LU400 GE LU1000 GE GE Evolve ERS4 Philips RoadView RVM Horner ETG Global Tech SoLtice LED Stray Light Optical Technologies, Tesla II Ecoluminator: PMX-ILS-200SL
27,500 50,000 130,000 30,000 20,500 20,775 19,400 27,136 23,000 20,000
110 125 130 94 79 77 97 81 78 100
Note: CCT is correlated color temperature; CRI is color rendering index. a per lamp. b per fixture.
CCT CRI Average life (K) (h) 2100 2000 2100 4100 5700 4300a 5000 4998 5500 5000
22 22 22 65 70 70 70 67 75 86
40,000 40,000 24,000 20,000 50,000 100,000 100,000 100,000 50,000 100,000
Warranty (yrs.)
Price ($)
1 1 1 1 5 5 3 5 5 5
54.40a 68.58a 105.70a 80.10a 800.00b 950.00b 850.00b 1750.00b 850.00b 500.00b
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the information on all selected luminaires. The three HPS luminaires include 250 W and 400 W cobra head luminaires for road-side lighting and 1000 W cobra head luminaires for high mast lighting typically utilized by INDOT. The four LED luminaires include GE ERS4 258 W luminaires, Philips RVM 270 W LED luminaires and Horner 200 W LED luminaires for road-side lighting, and Global Tech 392 W LED luminaires for high mast lighting. The EcoLuminator 200 W induction luminaires, Stray Light 295 W plasma luminaires, and GE 320 W MH luminaires were all selected for road-side lighting. Shown in Fig. 2 are the photos of the selected luminaires.
4.
Illuminance measurement
Light illuminance measurements were taken using an illuminance meter with a measuring range of 0.001e29,990 footcandles (fc). The illuminance meter can be operated at 10 C to 40 C, which allows possible light testing throughout the year, particularly in winters. During light testing, it was initially intended to take the light illuminance measurements with a 3 feet by 3 feet measuring grid over a 2-luminaire cycle in each of the conventional lighting test zones. However, preliminary field testing at the beginning revealed that it was not practical due to roadside objects, variations in lighting
Fig. 2 e Photos of HPS, LED, induction, plasma and MH luminaires. (a) 250/400 W HPS. (b) 6 £ 392 W LED. (c) GE 258 W LED. (d) Philips 270 LED. (e) Horner 200 W LED. (f) Stray light 295 W plasma. (g) Luxlite 200 W induction. (h) GE 310 W MH.
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layouts, and traffic control. Consequently, the midpoint of the measurement grid was longitudinally aligned with the middle pole over the 2-luminiare cycle in zones 1, 2, 3 and 4. The measurement points were set on a 10 feet 12 feet grid covering both shoulder and all traffic lanes, so as to place the measurement points on the lane markings and make it much easier for field testing. For the high mast lighting in zone 5, the measuring grid was laid out on a grid at 40 feet spacing in eight radial directions, such as east, south, west, north, north-east, south-east, north-west, and south-west. Fig. 3 shows the illuminance footprints (in foot-candles) of the luminaires in zone 1. It should be noted that each of the footprints represents only part of the corresponding lighted road surface area. Three observations can be made through careful inspection of the footprints. First, the HPS, GE LED and Philips LED luminaires produced oval-shaped lighted areas, while the lighted area by GE LED demonstrates two angles, one at each end. The Horner LED produced a circular lighted area. Second, the areas lighted by the HPS and GE
377
LED luminaires are very close in size and greater than those by the Philips and Horner LED luminaires. The Horner LED luminaire produced the smallest lighted area. Third, all four types of luminaires produced measureable illuminance of 0.05 foot-candles or greater between the lighting poles. The AASHTO guide for roadway lighting (AASHTO, 2005) requires a minimum illuminance of 0.2 foot-candles on pavement. The measured illuminance values indicate that the percentages of grid points with illuminance of at least 0.2 foot-candles are 98%, 96%, 94%, and 60% for the HPS, GE LED, Philips LED, and Horner LED luminaires, respectively. The illuminance distributions right under the targeted luminaires varied from luminaire to luminaire. For the HPS and GE LED luminaires, the illuminance measurements exhibited a double-hump distribution. The greatest illuminance occurred at two locations symmetrical to the luminaire. For the Philips LED and Horner LED luminaires, the illuminance measurements showed a single-hump distribution. The greatest illuminance occurred at only the pavement surface
Fig. 3 e Illuminance footprints in zone 1 (pole #2) (Note: SE is shoulder edge, PER is pavement edge on right, PEL is pavement edge on left, and CL is center line). (a) 250 W HPS. (b) GE 258 W LED (ERS4). (c) Philips 270 W LED (RVM). (d) Horner 200 W LED.
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right under the luminaire. The GE and Philips LED luminaires produced a lighted area greater than that produced by the Horner LED luminaire. However, the maximum illuminance produced by the Horner luminaire was greater than those by the GE or Philips LED luminaires, while the Horner LED lamp size was smaller than both the GE and Philips LED lamp sizes. The illuminance footprints of the luminaires in zones 2 and 3 are shown in Figs. 4 and 5. These two zones consisted of similar lighting pole layout. In zone 2, the three HPS lamps included two 400 W lamps and one 250 W lamp, with one of the 400 W lamps on the middle pole. In zone 3, the three HPS lamps consisted two 250 W lamps and one 400 W lamp, with one of the 250 W lamps on the middle pole. All luminaires in zones 2 and 3 produced measurable illumination between the lighting poles. In zone 2, the HPS, GE LED and Philips LED luminaires produced oval-shaped lighted areas, and the Horner LED luminaire produced a circular lighted area. The percentages of grid points with illuminance of at least 0.2 foot-candles are 98%, 88%, 78%, and 52% for the HPS, GE LED, Philips LED, and Horner LED luminaires, respectively. The luminaires in descending order of their lighted areas are HPS, GE LED, Philips LED, and
Horner LED. Compared with all LEDs, the HPS luminaire produced not only the largest lighted area, but also the greatest illuminance. In addition, the HPS light distribution is different from that in zone 1. The GE LED luminaire produced a double-hump illuminance distribution and both the Philips and Horner LED luminaires produced a singlehump illuminance distribution. The maximum illuminance produced by Horner LED is greater than those produced by the GE and Philips LEDs. In zone 3, the induction luminaire produced a circular lighted area and the other luminaries produced oval-shaped lighted areas. The percentages of grid points with illuminance of at least 0.2 foot-candles are 73%, 94%, 68%, and 45% for the HPS, GE LED, Philips LED, and induction luminaires, respectively. The GE LED produced the largest lighted area with a double-hump illuminance distribution. The illuminance footprints by the HPS, Philips LED and induction lightings showed a single-hump distribution in the lighted areas. The lighted areas by HPS and Philips LED are very close in terms of the size and shape of the lighted area. The induction luminaire produced the smallest lighted area. Both the GE and Philips LEDs produced a maximum illuminance
Fig. 4 e Illuminance footprints in zone 2 (pole #6). (a) 400/400/250 W HPS. (b) GE 258 W LED (ERS4). (c) Philips 270 W LED (RVM). (d) Horner 200 W LED.
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Fig. 5 e Illuminance footprints in zone 3 (pole #9). (a) 250/250/400 W HPS. (b) GE 258 W LED. (c) Philips 270 W LED (RVM). (d) EcoLuminator 200 W induction.
greater than that produced by either the HPS or induction luminaire. The maximum illuminance by the induction luminaire is slightly greater than that by the HPS luminaire. It is also interesting to note that the lighted areas in zone 1 are greater than the lighted areas produced by the same luminaires in zones 2 and 3. This is influenced by the nearby restaurant lightings in zone 1. Fig. 6 presents the footprints of the 400 W HPS and Stray Light 295 W plasma luminaires in zone 4. Due to the different measurement grids utilized in the shoulder and in the driveway, the footprints were plotted separately. It is shown that in general, these two different luminaires produced measurable illumination over the 270 ft spacing. Both the HPS and plasma luminaires produced oval-shaped lighted areas. The footprints peak right below the luminaires. However, the lighted area produced by the 400 W HPS luminaires is much greater than that by the 295 W plasma luminaires. Approximately 71% of the lighted area was covered with 0.20 foot-candles or greater with the
HPS luminaire and only 49% of the lighted area was covered with 0.20 foot-candles or greater with the plasma luminaire. In addition, the HPS luminaire produced greater illuminance than the plasma luminaire. In zone 5, a total of 40 measurements were taken around the high mast light pole. The illuminance measuring started from the HM pole and ended at the edge of roadside ditches as illustrated in Fig. 7. Fig. 8 shows the illuminance measurements in foot-candles taken in the eight radial directions of the high mast tower lighting. The W-E line indicates the illuminance measurements taken in both the west and east directions, respectively. The N-S line indicates the illuminance measurements taken in both the north and south directions, respectively. The NE-SW line indicates the illuminance measurements taken in both the northeast and southwest directions, respectively. The NWSE line indicates the illuminance measurements taken in both the northwest and southeast directions, respectively. Two major observations can be made through careful
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Fig. 6 e Illuminance footprints in zone 4 (pole #15) (Note: LML is lane marking on left, LMR is lane marking on right). (a) 400 W HPS measured in shoulder. (b) 400 W HPS measured in driveway. (c) Stray light Tesla II 295 W plasma measured in shoulder. (d) Stray light Tesla II 295 W plasma measured in driveway.
inspections of these illuminance curves. First, both types of luminaires produced a symmetrically lighted, circular area with relatively large foot-candles. The illuminance measurements of at least 0.20 foot-candles covered 100% of the lighted area with both the HPS and SoLtice LED luminaires. Second, the light illuminance produced by the 1000 W HPS luminaires was much greater than that by the SoLtice 392 W luminaires.
5.
Performance evaluation
The average maintained horizontal illuminance and uniformity ratio are the two key design values for implementing roadway lightings. Tables 3 and 4 present the road surface classifications and the roadway illuminance design values
specified by AASHTO (2005). Three design indicators are recommended in the AASHTO standard, including average maintained illuminance, minimum illuminance, and uniformity ratio. The average maintained horizontal illuminance is the average level of horizontal illuminance on the pavement area of calculation or measurement. For straight roadways, the area should cover one luminaire cycle, which is defined as the area between two poles along one side of the roadway. Uniformity ratio is defined as the ratio of average illuminance to the minimum illuminance in the area. Lower uniformity ratio indicates less frequent contrasts on the lighted roadway segments so that road users can perceive roadway conditions continuously with less discomforts. However, if the uniformity ratio is too low when the brightness is low, the visibility could be reduced, making it difficult for drivers to distinguish objects and roadway features.
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Fig. 7 e Field measurement points in test zone 5. According to the types of pavements and roadways, zones 1, 2 and 3 are classified as R2 surface on other principal arterials of intermediate land use, and zone 4 as R2 surface on interstate of intermediate land use. Because the high mast luminaires serve as interchange lighting, zone 5 does not fit into any of the AASHTO roadway lighting categories. Based on the AASHTO recommendations from Tables 3 and 4, the illuminance values used for evaluation of the lighting zones are summarized in Table 5. Presented in Table 6 are the measured illuminance metrics for the five zones. In order to evaluate the performance of the tested luminaires, the measured illuminance values and uniformity ratios of the new types of luminaries are compared with those of the HPS luminaires as well as with the recommended values in Table 5. The measured illuminance values and uniformity ratios of the luminaires in zone 1 are plotted in Fig. 9. As shown in Table 5, the recommended minimum average maintained illuminance is 1.2 foot-candles and the maximum uniformity ratio is 3. The measured average illuminance values are 1.00, 1.20, 0.87, and 0.80 foot-candles for HPS, GE LED, Philips LED, and Horner LED, respectively. Only GE LED met the AASHTO recommended for average illuminance. Each of the three types of LED luminaires produced a maximum illuminance greater than that by the HPS. The HPS had the lowest
uniformity ratio (5.8) followed by Philips LED (5.9). Therefore, in terms of average illuminance, the GE LED luminaires appear to be the best type of luminaires to replace HPS even though their high uniformity ratios are not desirable. Fig. 10 illustrates the measured illuminance values and uniformity ratios of the luminaires in zone 2. Same as zone 1, the recommended minimum average maintained illuminance is 1.2 foot-candles and the maximum uniformity ratio is 3 for zone 2. The measured average illuminance values are 1.33, 1.00, 0.89, and 0.82 foot-candles for HPS, GE LED, Philips LED, and Horner LED, respectively. As can be seen, the minimum, maximum and average illuminance values produced by the HPS are greater than those by the three types of LEDs in zone 2. In addition, the HPS's uniformity ratio is the lowest. Therefore, the HPS luminaires performed better than all these types of LEDs under the conditions in zone 2. Fig. 11 illustrates the measured illuminance values and uniformity ratios of the luminaires in zone 3. Same as the first two zones, the recommended minimum average maintained illuminance is 1.2 foot-candles and the maximum uniformity ratio is 3. The measured average illuminance values are 0.63, 0.50, 1.11, 0.84, and 0.55 footcandles for HPS, EcoLuminator induction, GE LED, Philips LED, and Metal Halide, respectively. Although none of the
Fig. 8 e High mast lighting illuminance distributions in zone 5. (a) Six 1000 W HPS luminaires. (b) Six SoLtice 392 W LED luminaires.
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Table 3 e AASHTO road surface classifications. Class
Mean luminance coefficient (Q0)
Description
R1
0.10
R2
0.07
R3
0.07
R4
0.08
Portland cement concrete road surface. Asphalt road surface with a minimum of 12% of the aggregates composed of artificial brightener aggregates. Asphalt road surface with an aggregate composed of minimum 60% gravel. Asphalt road surface with 10%e15% artificial brightener in aggregate mix. Asphalt road surface with dark aggregates; rough texture after some months of use. Asphalt road surface with very smooth texture.
Mode of reflectance Mostly diffuse
Mixed (diffuse and specular)
Slightly specular Mostly specular
Table 4 e AASHTO illuminance design values for continuous roadway lighting. Roadway classification
Principal arterials - interstate and other freeways Principal arterials - others
Minor arterials
Collectors
Local
General land use
Commercial Intermediate Residential Commercial Intermediate Residential Commercial Intermediate Residential Commercial Intermediate Residential Commercial Intermediate Residential
Average maintained illuminance (fc) R1
R2
R3
R4
0.6 to 1.1 0.6 to 0.9 0.6 to 0.8 1.1 0.8 0.6 0.9 0.8 0.5 0.8 0.6 0.4 0.6 0.5 0.3
0.6 to 1.1 0.6 to 0.9 0.6 to 0.8 1.6 1.2 0.8 1.4 1.0 0.7 1.1 0.8 0.6 0.8 0.7 0.4
0.6 to 1.1 0.6 to 0.9 0.6 to 0.8 1.6 1.2 0.8 1.4 1.0 0.7 1.1 0.8 0.6 0.8 0.7 0.4
0.6 to 1.1 0.6 to 0.9 0.6 to 0.8 1.4 1.0 0.8 1.0 0.9 0.7 0.9 0.8 0.5 0.8 0.6 0.4
Table 5 e Recommended values of illuminance performance evaluation. Zone
1 2 3 4 5
Minimum average Minimum Maximum maintained illuminance illuminance uniformity (foot-candle) ratio 1.2 1.2 1.2 0.6 to 0.9 N/A
N/A N/A N/A 0.2 N/A
3 3 3 3 or 4 N/A
luminaires had illuminance higher than 1.20, GE LED provided the highest illuminance value of 1.11. The illuminance values of the induction luminaires and the metal halide luminaires are relatively low. As Table 5 shows, the AASHTO recommended minimum average illuminance, minimum illuminance, and uniformity ratio for zone 4 are 0.6e0.9 foot-candles, 0.2 foot-candles, and 3e4, respectively. Fig. 12 illustrates the measured illuminance values and uniformity ratios of the luminaires in zone 4. Both HPS and Plasma luminaires satisfy minimum average maintained illuminance requirement, but not the minimum illuminance requirement. The uniformity ratios of the two types of luminaires are greater than the recommended value. The performance of the HPS
Minimum illuminance
Uniformity ratio
0.2 0.2 0.2 As uniformity ratio allows
3 or 4 3 or 4 3 or 4 3 3 3 4 4 4 4 4 4 6 6 6
luminaires is better than that of the Plasma luminaires in terms of the minimum average illuminance, minimum illuminance, and uniformity ratio. However, it should be pointed out that the power of the Plasma luminaires (295 W) is much lower than that of the HPS luminaires (400 W). Therefore, the electricity consumption should be considered in the life cycle cost analysis of different types of lighting devices (Jiang et al., 2015). As shown in Table 6 and Fig. 13, in zone 5, the minimum, maximum and average illuminance values produced by the 392 W tech LED luminaires are much smaller than those by the 1000 W HPS luminaires. However, the illuminance uniformity ratio with the tech LED luminaires is smaller than that with the HPS luminaires. Because of the great difference between the powers of the two types of luminaires, the LED luminaires saved a great deal of electricity.
6.
Conclusions
Through a field study of various types of luminaires, the performances of the luminaires were evaluated and compared to the HPS luminaires. Compared to HPS 250 W luminaires, both the GE 258 W and Philips 270 W LED luminaires produced similar minimum illuminance and the Horner LED and
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Table 6 e Measured illuminance metrics in different test zones. Zone
1
2
3
4 5
Luminaire type
HPS (250W) GE LED (258W) Philips LED (270W) Horner LED (200W) HPS (250W) GE LED (258W) Philips LED (270W) Horner LED (200W) HPS (250W) EcoLuminator induction (200W) GE LED (258W) Philips LED (270W) Metal Halide (320W) HPS (400W) Stray light plasma (295W) HPS (6 1000W) Global tech LED (6 392W)
Illuminance (foot-candle)
Uniformity ratio
Min
Max
Avg
0.17 0.16 0.15 0.10 0.15 0.08 0.09 0.04 0.07 0.02 0.15 0.09 0.08 0.14 0.04 0.66 0.26
3.25 4.03 3.67 4.42 5.15 3.62 3.66 4.42 2.15 2.70 3.87 3.61 1.94 3.86 3.52 5.05 1.53
1.00 1.20 0.87 0.80 1.33 1.00 0.89 0.82 0.63 0.50 1.11 0.84 0.55 1.00 0.77 2.88 0.80
5.8 7.6 5.9 8.2 8.8 12.8 10.2 19.1 9.0 22.7 7.6 9.2 6.6 7.1 21.9 4.4 3.1
Fig. 9 e Illuminances and uniformity ratios of luminaires in zone 1. (a) Illuminances. (b) Uniformity ratios.
EcoLuminator induction 200 W luminaires produced smaller minimum illuminance. The maximum illuminance values produced by these LED and induction luminaires are all greater than that by the HPS 250 W luminaires. The GE LED produced the greatest average illuminance and the Horner LED produced the smallest average illuminance. The illuminance uniformity ratio of the Philips LED is slightly better than that of HPS 250 W. The illuminance uniformity ratio of the GE LED luminaires is slightly greater than that of the HPS 250 W. The illuminance uniformity ratios of the Horner LED and EcoLuminator induction luminaires are much greater than those of the GE LED, Philips LED and HPS luminaires.
Compared to HPS 400 W luminaires, the LED and plasma luminaires produced smaller minimum, maximum and average illuminance values. The illuminance uniformity ratios of the LED and plasma luminaires are greater than those of the HPS luminaires. The GE and Philips LED luminaires produced greater average illuminance and smaller illuminance ratio values than the Horner LED and Stray light plasma luminaires. For high mast lighting, the SoLtice 392 E LED luminaires produced smaller illuminance levels but better uniformity than the HPS 1000 W luminaires. Taking into account the light performance presented in this paper, it is recommended that the LED lighting
Fig. 10 e Illuminances and uniformity ratios of luminaires in zone 2. (a) Illuminances. (b) Uniformity ratios.
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Fig. 11 e Illuminances and uniformity ratios of luminaires in zone 3. (a) Illuminances. (b) Uniformity ratios.
Fig. 12 e Illuminances and uniformity ratios of luminaires in zone 4. (a) Illuminances. (b) Uniformity ratios.
Fig. 13 e Illuminances and uniformity ratios of luminaires in zone 5. (a) Illuminances. (b) Uniformity ratios.
technologies be adopted for roadway lighting applications. In particularly, the GE 258 W, Philips 270 W, and Horner 200 W LED luminaires may be used to replace the HPS 250 W luminaires with the existing lighting poles. The GE 258 W and Philips 270 W LED luminaires may also be used to replace the HPS 400 W luminaires. The SoLtice LED 392 W luminaires may be used to replace the HPS 1000 W luminaires in high mast lightings. The potential concern associated with use of the new lighting is the light uniformity. It is recommended that further efforts be made by manufacturers to enhance the light uniformity for roadway lighting applications with the existing lighting poles. Field application data on the long-term performance and reliability is still needed for future revision of the design criteria for the new lighting technologies.
Conflicts of interest The authors do not have any conflict of interest with other entities or researchers.
Acknowledgments This work was supported in part by the Joint Transportation Research Program administered by the Indiana Department of Transportation (INDOT) and Purdue University. The authors would like to thank the study advisory committee members, Bill Smith, Todd Shields, Dana Plattner, and Ting Nahrwold of
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INDOT and Karen Stippich (FHWA) for their guidance and expertise. Sincere thanks are extended to Monty Wilson and Alan Sosbe and their crew members for their help and support in field installation and traffic control. The authors recognize the assistance provided by Tony Johnson, Harry Greer, Patrick Weaver, Maurice Hendrix, Hobert Deaton, and Robert White in field light testing.
references
AASHTO, 2005. AASHTO Roadway Lighting Design Guide. American Association of State Highway and Transportation Officials (AASHTO), Washington DC. Bullough, J.D., Leora, C., Radetsky, L.C., 2013. Analysis of New Highway Lighting Technologies. National Cooperative Highway Research Program (NCHRP), Washington DC. ETC, 2017. Induction Lamps. Edition Tech Center (ETC). Available at: http://www.edisontechcenter.org/InductionLamps.html (Accessed 12 December 2017). Halonen, L., Tetri, E., Bhusal, P., 2010. Guidebook on Energy Efficient Electric Lighting for Buildings. Aalto University, Aalto. HMC, 2005. LED. The American Heritage Science Dictionary. Houghton Mifflin Company (HMC), Boston. IES, 2008. Electrical and Photometric Measurements of Solid-state Lighting Products. LM-79-08. Illuminating Engineering Society (IES), New York. INDOT, 2012. Design Specifications. Indiana Department of Transportation, Indianapolis.
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Jiang, Y., Li, S., Guan, B., et al., 2015. Cost effectiveness of new roadway lighting systems. Journal of Traffic and Transportation Engineering (English Edition) 2 (3), 158e166. LSC, 2017. How Do Metal Halide Lamps Work? Available at: http:// www.lrc.rpi.edu/programs/nlpip/lightingAnswers/mwmhl/ work.asp (Accessed 12 December 2017). Moreno, I., Sun, C., 2008. Modeling the radiation pattern of LEDs. Optics Express 16 (3), 1808e1819. Philips, 2017. LED Lighting. Available at: http://www.lighting. philips.com/main/education/led-lighting (Accessed 12 December 2017). Plasma Globe, 2018. Available at: http://en.wikipedia.org/wiki/ plasma_globe (Accessed 19 July 2018). USDOE, 2010. High-Intensity Discharge Lamps: Analysis of Potential Energy Savings. Energy Efficiency Program for Commercial and Industrial Equipment. EE-det-03-001. U.S. Department of Energy (USDOE), Washington DC.
Dr. Yi Jiang received his Bachelor degree in civil engineering from Tongji University in China. He received his Master's and PhD degrees in civil engineering from Purdue University in the USA. He worked in the Indiana Department of Transportation as a highway engineer and section manager before joining the faculty at Purdue University. Dr. Jiang is a full professor in the Department of Building Construction Management at Purdue University.
Available online at www.sciencedirect.com
ScienceDirect journal homepage: www.elsevier.com/locate/jtte
Original Research Paper
Field evaluation of selected light sources for roadway lighting Yi Jiang a,*, Shuo Li b, Bowen Guan c, Guangyuan Zhao a, Dave Boruff d, Lalit Garg d, Prakash Patel d a
Department of Building Construction Management, Purdue University, West Lafayette, IN 47907, USA Division of Research and Development, Indiana Department of Transportation, West Lafayette, IN 47906, USA c School of Materials Science and Engineering, Chang'an University, Xi'an 710064, China d Indiana Department of Transportation, Indianapolis, IN 46204, USA b
highlights The illuminance values of various types of devices were measured under actual roadway lighting conditions. The performances of the luminaires were evaluated and compared to the conventional HPS luminaires in both roadside lighting and high mast lighting. LED lighting technologies were recommended for roadway lighting applications. It was recommended that further efforts be made by manufacturers to improve the light uniformity.
article info
abstract
Article history:
The development of new lighting sources, such as light emitting diode (LED), induction,
Received 18 February 2018
and plasma, presented more possible cost effective ways for roadway lighting. A study was
Received in revised form
therefore conducted for the Indiana Department of Transportation (INDOT) to evaluate the
20 May 2018
performance and effectiveness of some selected new lighting devices in roadway lighting.
Accepted 23 May 2018
This paper describes the field evaluation process and presents the evaluation results. A
Available online 6 August 2018
number of LEDs, plasma and induction luminaires from various manufacturers were selected to replace the existing high pressure sodium (HPS) lamps in conventional and high
Keywords:
mast lightings. Illuminance values were measured over a period of 12 months on the
Roadway lighting
existing and new light sources. Light performance metrics, including illuminance level and
Luminaires
uniformity ratios, were calculated to make quantitative comparisons of the HPS and new
Illuminance
types of light devices. Based on the evaluation in terms of lighting performance and life
Field tests
cycle costs, it was concluded that LED luminaires should be utilized in roadway lighting in
LED
place of HPS luminaires. The results of this study will be useful to state highway and city
HPS
street agencies in making decisions on their lighting policies and developing technical specifications for use of the new lighting technologies in roadway and street lightings. The study provides a basis for manufacturers to improve their luminaire design and integration to better fit the needs of roadway and street lightings.
* Corresponding author. Tel.: þ1 765 409 0670. E-mail addresses: [email protected] (Y. Jiang), [email protected] (S. Li), [email protected] (B. Guan), [email protected] (G. Zhao), [email protected] (D. Boruff), [email protected] (L. Garg), [email protected] (P. Patel). Peer review under responsibility of Periodical Offices of Chang'an University. https://doi.org/10.1016/j.jtte.2018.05.002 2095-7564/© 2018 Periodical Offices of Chang'an University. Publishing services by Elsevier B.V. on behalf of Owner. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
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© 2018 Periodical Offices of Chang'an University. Publishing services by Elsevier B.V. on behalf of Owner. This is an open access article under the CC BY-NC-ND license (http:// creativecommons.org/licenses/by-nc-nd/4.0/).
1.
Introduction
There is an increasing interest in using new lighting technologies in roadway and street lightings. The new lighting technologies include light emitting diode (LED), induction and plasma light sources. The most commonly claimed benefits of the new light sources include increased reliability, improved efficiency, and reduced maintenance costs. Due to this growing interest and demand, an NCHRP study (Bullough et al., 2013) was conducted to evaluate the potential and proper application of LED lighting technology. They concluded that efficiency and photometric performance had evolved to the point that LED roadway lighting was a feasible choice and could often lead to reductions in energy use of around 15% or greater, or life-cycle cost reductions in the long term, depending upon the initial cost of LED luminaires. However, specific luminaires using LED sources can have a wide range of performance, and should be judged on an individual luminaire basis. The Indiana Department of Transportation (INDOT) has been contacted by vendors requesting possible application of the new light sources for roadway lighting. Before adopting the new lighting systems, INDOT would like to determine if the new lighting systems meet required light output and if they are cost effective. Moreover, it is necessary for INDOT to establish standardized guidelines for evaluating the new lighting systems prior to the formal adoption. This study was conducted to evaluate some selected lighting devices in roadway lighting. The major effort of this study was to address engineering issues, such as light levels, life cycle cost, maintenance, traffic safety, and approval procedures for new lighting technologies based on field evaluations. The evaluations include the properties, benefits and costs, and effectiveness of selected new lighting devices in roadway lighting applications. Illuminance values were measured over a period of 12 months on the existing and new light sources to identify light distributions. Light performance metrics in terms of illuminance levels and uniformity ratios were calculated to make quantitative comparisons between the lighting performances of the existing and new lighting devices. It is believed that the information presented in this paper will be useful to state highway and city street agencies in making decisions on their lighting policies and developing technical specifications for use of the new lighting technologies in roadway and street lightings. It is also believed that such information is useful for manufacturers to improve their luminaire model design and integration to better fit the needs of roadway and street lightings.
2.
Highway lighting luminaires
2.1.
HPS lamps
There are three types of lighting sources that have been widely used for indoor and outdoor lighting applications, including incandescent, fluorescent, and high intensity discharge (HID) lights. For highway facilities, lighting is commonly provided at interchanges, rest areas, weight stations, tunnels, and parking lots. The HID light source family consists mainly of four members, including mercury vapor (MV), low-pressure sodium (LPS), high pressure sodium (HPS), and metal halide (MH) lights. HPS is the most commonly used for roadway lighting. HPS luminaires are the main lighting source for almost all state-owned highways in Indiana (INDOT, 2012). HPS lamps were introduced in the 1960s. An HPS lamp commonly consists of four basic components, including a sealed, translucent, ceramic arc tube, main electrodes, an outer bulb, and a base (Halonen et al., 2010; USDOE, 2010). The arc tube ceramic contains a mixture of a small amount of xenon gas and sodium-mercury amalgam and is used to provide a proper environment for producing light. The xenon at a low pressure is used as a “starter gas” in the HPS lamp. Lying at the coolest part of the lamp, the sodiummercury amalgam provides the sodium-mercury vapor that is needed to draw an arc. The main electrodes are made of tungsten and carry a high-voltage, high-frequency pulse to strike the arc and vaporize the mercury and sodium. The outer bulb, typically elliptical in shape and made of hard glass, protects the arc tube from damage and prevents oxidation of the internal parts. It also contains a vacuum that reduces convection and heat losses from the arc tube to maintain high efficacy. The lamp base is typically a screwed base made of brass or nickel and provides a socket for electrical connection. An HPS lamp requires an inductive ballast to regulate the arc current flow and deliver the proper voltage to the arc.
2.2.
MH lamps
MH lamps are also a member of HID lamp family. MH lamps can offer an excellent combination of quality and performance. MH lamps not only present more natural blue-white light compared to HPS lamps, but also provide increased efficacy compared to MV lamps. A standard MH lamp consists of four basic components, including quartz arc tube, main electrodes, outer bulb, and base. The operation of metal halide lamps is similar to HPS lamps in that they produce light by way of an arc tube contained within a glass bulb (LSC, 2017). When an MH lamp is energized, the
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Fig. 1 e Map of light test site.
electric current passes through the arc tube and ignites an electric arc through a gaseous mixture of vaporized mercury and metal halides, which are compounds of metals with bromine or iodine. Similar to HPS lamps, inductive ballast is used to regulate the current and the voltage to the lamp.
2.3.
LED lighting
LED lighting is a type of solid-state lighting. It is a semiconductor based device that produces light when an electrical current passes through it. Multiple LEDs can be combined into LED arrays. LED lamp, as defined by IES (2008), is an LED device with an integrated driver and a standardized base that is designed to connect to the branch circuit via a standardized lamp holder/socket. An LED is a two-lead semiconductor light source. It is a pen junction diode that emits light when activated (HMC,
2005). When a suitable voltage is applied to the leads, electrons are able to recombine with electron holes within the device, releasing energy in the form of photons. LEDs are typically small (less than 1 mm2) and integrated optical components may be used to shape the radiation pattern (Moreno and Sun, 2008). A basic LED luminaire consists of optical, electrical, mechanical, and thermal components (Halonen et al., 2010; Philips, 2017). When an electron meets a hole, the electron falls into a lower energy state and releases a particle known as a photon, which is where the visible light comes from. A heat sink is needed to draw the heat away from the LED array. The heat sink is typically integrated into the outer housing of the fixture to maximize heat dissipation. With the advancements in optics and semi-conducting technologies, LED technologies have become more reliable, and the prices of LED luminaires have continuously declined. As a result, LED lighting applications have become more financially attainable.
Table 1 e Geometric dimensions of lighting poles. Test zone
1
2
3
4
5
Pole#
1 2 3 4 6 7 8 9 10 14 15 16 T-2
EMH (ft)
42
42
42
42
125
Pole spacing
MAL (ft)
Pole setback (ft)
Design
Measured
Design
Measured
Design
e 275 280 e 300 280 e 290 290 e 270 270 N.A.
e 273 277 e 340 280 e 289 287 e 270 274 N.A.
15
18
20
15
16
15
15
15
18
e
e
Measured
20.0 19.5 20.6 20 8.7 20.4 21.0 20 20.4 22.4 20.6 20 23.5 20 24.3 15 21.1 225 (offset from US 231)
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2.4.
Plasma lighting
3.
Plasma, also known as lighting emitting Plasma (LEP), is an ionized gas with equal number of positive and negative charges. Plasma lamps are electrodeless lamps, meaning there are no electrical connections inside of the bulb, which use radio frequency (RF) waves to excite Plasma within the bulb. A plasma lamp is usually a clear glass sphere filled with a mixture of various gases, such as neon, argon, xenon and krypton, at nearly atmospheric pressure. They are driven by high-frequency alternating current. The drive circuit is essentially a specialized power inverter. The radio-frequency energy from the transformer is transmitted into the gas within the globe through an electrode at its center. The radiofrequency energy is admitted into the larger space by capacitive coupling right through the glass. Plasma filaments extend from the inner electrode to the outer glass insulator, giving the appearance of moving tendrils of colored light within the volume of the globe (Plasma globe, 2018).
2.5.
Induction lighting
Induction lamps are another form of an electrode-less lamp. An induction lamp consists of three major components, including ballast (known as HF generator), power coupler, and lamp bulb (ETC, 2017). The ballast contains an oscillator and preconditioning and filtering circuits. It first converts AC to DC, and then DC to AC. The power coupler contains an antenna which is made of a primary induction coil and ferrite core. It transfers energy from the ballast to the discharge inside the lamp bulb. The lamp bulb is a sealed glass bulb containing a low pressure inert gas with a small amount of mercury vapor. When an induction lamp is powered, the ballast generates HF current. The HF current is sent through the electromagnet and a strong magnetic field is produced. The energy is transferred from the magnet to the mercury in the tube via the antenna and excites the mercury atoms. The mercury vapor emits ultraviolet light which is changed into visible light by the phosphor coating on the inside of the glass.
Test site and selected luminaires
The test site was located near the interchange of I-74 and US231 in the vicinity of Crawfordsville, Indiana, as shown in Fig. 1. The site was selected in the consideration of easy luminaire installation, illuminance measurement, and traffic control set up. The site was divided into five test zones to expedite the evaluation process during the study period. Lightings in zones 1 to 4 were all road-side lightings with single-sided layout. The lighting in zone 5 was a high mast lighting. Zone 1 was located on US-231 northbound, consisting of three lighting poles, denoted as poles 1, 2 and 3 (two luminaire cycles). The road segment consisted of two through lanes and one turning lane. Zones 2 and 3 were located on US-231 southbound, each consisting of three lighting poles, denoted as poles 4, 6 and 7 in zone 2, and poles 8, 9 and 10 in zone 3. The road segments in zones 2 and 3 consisted of one through lane and one turning lane. Zone 4 was located on I-74 westbound, consisting of poles 14, 15 and 16. The road segment had two through lanes and one merging lane. Zone 5 was the upper quadrant of the interchange with a single high mast lighting pole, i.e., T-2, covering a 2-way ramp, part of interchange and a signalized, 3-leg intersection of US-231 and the ramp. Presented in Table 1 are the layouts and geomertic dimensions of the current lighting poles in these five test zones. Field visits were conducted to verify the design dimensions of the light poles. It was found that most measured dimensions agree well with the design dimensions, except for the pole spacing between poles 4 and 6. The effective mounting height (EMH) is 42 feet for all road-side lighting poles and 125 feet for the HM lighting pole. Discrepancies were observed between the design mast arm length (MAL) and measured MAL as well as between the measured pole setback and the design pole setback. The INDOT records indicated that the light poles were installed in 1993 in this test site. A total of ten types of luminaire were selected by the INDOT engineers according to the product availabilities and the vendor/manufacturer recommendations. Table 2 presents
Table 2 e Information on selected luminaries. Type 250 W, HPS 400 W, HPS 1000 W, HPS 320 W, MH 258 W, LED 270 W, LED 200 W, LED 392 W, LED 295 W, plasma 200 W, induction
Manufacturer model
Initial lumens
Lamp efficacy
GE LU250 GE LU400 GE LU1000 GE GE Evolve ERS4 Philips RoadView RVM Horner ETG Global Tech SoLtice LED Stray Light Optical Technologies, Tesla II Ecoluminator: PMX-ILS-200SL
27,500 50,000 130,000 30,000 20,500 20,775 19,400 27,136 23,000 20,000
110 125 130 94 79 77 97 81 78 100
Note: CCT is correlated color temperature; CRI is color rendering index. a per lamp. b per fixture.
CCT CRI Average life (K) (h) 2100 2000 2100 4100 5700 4300a 5000 4998 5500 5000
22 22 22 65 70 70 70 67 75 86
40,000 40,000 24,000 20,000 50,000 100,000 100,000 100,000 50,000 100,000
Warranty (yrs.)
Price ($)
1 1 1 1 5 5 3 5 5 5
54.40a 68.58a 105.70a 80.10a 800.00b 950.00b 850.00b 1750.00b 850.00b 500.00b
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the information on all selected luminaires. The three HPS luminaires include 250 W and 400 W cobra head luminaires for road-side lighting and 1000 W cobra head luminaires for high mast lighting typically utilized by INDOT. The four LED luminaires include GE ERS4 258 W luminaires, Philips RVM 270 W LED luminaires and Horner 200 W LED luminaires for road-side lighting, and Global Tech 392 W LED luminaires for high mast lighting. The EcoLuminator 200 W induction luminaires, Stray Light 295 W plasma luminaires, and GE 320 W MH luminaires were all selected for road-side lighting. Shown in Fig. 2 are the photos of the selected luminaires.
4.
Illuminance measurement
Light illuminance measurements were taken using an illuminance meter with a measuring range of 0.001e29,990 footcandles (fc). The illuminance meter can be operated at 10 C to 40 C, which allows possible light testing throughout the year, particularly in winters. During light testing, it was initially intended to take the light illuminance measurements with a 3 feet by 3 feet measuring grid over a 2-luminaire cycle in each of the conventional lighting test zones. However, preliminary field testing at the beginning revealed that it was not practical due to roadside objects, variations in lighting
Fig. 2 e Photos of HPS, LED, induction, plasma and MH luminaires. (a) 250/400 W HPS. (b) 6 £ 392 W LED. (c) GE 258 W LED. (d) Philips 270 LED. (e) Horner 200 W LED. (f) Stray light 295 W plasma. (g) Luxlite 200 W induction. (h) GE 310 W MH.
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layouts, and traffic control. Consequently, the midpoint of the measurement grid was longitudinally aligned with the middle pole over the 2-luminiare cycle in zones 1, 2, 3 and 4. The measurement points were set on a 10 feet 12 feet grid covering both shoulder and all traffic lanes, so as to place the measurement points on the lane markings and make it much easier for field testing. For the high mast lighting in zone 5, the measuring grid was laid out on a grid at 40 feet spacing in eight radial directions, such as east, south, west, north, north-east, south-east, north-west, and south-west. Fig. 3 shows the illuminance footprints (in foot-candles) of the luminaires in zone 1. It should be noted that each of the footprints represents only part of the corresponding lighted road surface area. Three observations can be made through careful inspection of the footprints. First, the HPS, GE LED and Philips LED luminaires produced oval-shaped lighted areas, while the lighted area by GE LED demonstrates two angles, one at each end. The Horner LED produced a circular lighted area. Second, the areas lighted by the HPS and GE
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LED luminaires are very close in size and greater than those by the Philips and Horner LED luminaires. The Horner LED luminaire produced the smallest lighted area. Third, all four types of luminaires produced measureable illuminance of 0.05 foot-candles or greater between the lighting poles. The AASHTO guide for roadway lighting (AASHTO, 2005) requires a minimum illuminance of 0.2 foot-candles on pavement. The measured illuminance values indicate that the percentages of grid points with illuminance of at least 0.2 foot-candles are 98%, 96%, 94%, and 60% for the HPS, GE LED, Philips LED, and Horner LED luminaires, respectively. The illuminance distributions right under the targeted luminaires varied from luminaire to luminaire. For the HPS and GE LED luminaires, the illuminance measurements exhibited a double-hump distribution. The greatest illuminance occurred at two locations symmetrical to the luminaire. For the Philips LED and Horner LED luminaires, the illuminance measurements showed a single-hump distribution. The greatest illuminance occurred at only the pavement surface
Fig. 3 e Illuminance footprints in zone 1 (pole #2) (Note: SE is shoulder edge, PER is pavement edge on right, PEL is pavement edge on left, and CL is center line). (a) 250 W HPS. (b) GE 258 W LED (ERS4). (c) Philips 270 W LED (RVM). (d) Horner 200 W LED.
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right under the luminaire. The GE and Philips LED luminaires produced a lighted area greater than that produced by the Horner LED luminaire. However, the maximum illuminance produced by the Horner luminaire was greater than those by the GE or Philips LED luminaires, while the Horner LED lamp size was smaller than both the GE and Philips LED lamp sizes. The illuminance footprints of the luminaires in zones 2 and 3 are shown in Figs. 4 and 5. These two zones consisted of similar lighting pole layout. In zone 2, the three HPS lamps included two 400 W lamps and one 250 W lamp, with one of the 400 W lamps on the middle pole. In zone 3, the three HPS lamps consisted two 250 W lamps and one 400 W lamp, with one of the 250 W lamps on the middle pole. All luminaires in zones 2 and 3 produced measurable illumination between the lighting poles. In zone 2, the HPS, GE LED and Philips LED luminaires produced oval-shaped lighted areas, and the Horner LED luminaire produced a circular lighted area. The percentages of grid points with illuminance of at least 0.2 foot-candles are 98%, 88%, 78%, and 52% for the HPS, GE LED, Philips LED, and Horner LED luminaires, respectively. The luminaires in descending order of their lighted areas are HPS, GE LED, Philips LED, and
Horner LED. Compared with all LEDs, the HPS luminaire produced not only the largest lighted area, but also the greatest illuminance. In addition, the HPS light distribution is different from that in zone 1. The GE LED luminaire produced a double-hump illuminance distribution and both the Philips and Horner LED luminaires produced a singlehump illuminance distribution. The maximum illuminance produced by Horner LED is greater than those produced by the GE and Philips LEDs. In zone 3, the induction luminaire produced a circular lighted area and the other luminaries produced oval-shaped lighted areas. The percentages of grid points with illuminance of at least 0.2 foot-candles are 73%, 94%, 68%, and 45% for the HPS, GE LED, Philips LED, and induction luminaires, respectively. The GE LED produced the largest lighted area with a double-hump illuminance distribution. The illuminance footprints by the HPS, Philips LED and induction lightings showed a single-hump distribution in the lighted areas. The lighted areas by HPS and Philips LED are very close in terms of the size and shape of the lighted area. The induction luminaire produced the smallest lighted area. Both the GE and Philips LEDs produced a maximum illuminance
Fig. 4 e Illuminance footprints in zone 2 (pole #6). (a) 400/400/250 W HPS. (b) GE 258 W LED (ERS4). (c) Philips 270 W LED (RVM). (d) Horner 200 W LED.
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Fig. 5 e Illuminance footprints in zone 3 (pole #9). (a) 250/250/400 W HPS. (b) GE 258 W LED. (c) Philips 270 W LED (RVM). (d) EcoLuminator 200 W induction.
greater than that produced by either the HPS or induction luminaire. The maximum illuminance by the induction luminaire is slightly greater than that by the HPS luminaire. It is also interesting to note that the lighted areas in zone 1 are greater than the lighted areas produced by the same luminaires in zones 2 and 3. This is influenced by the nearby restaurant lightings in zone 1. Fig. 6 presents the footprints of the 400 W HPS and Stray Light 295 W plasma luminaires in zone 4. Due to the different measurement grids utilized in the shoulder and in the driveway, the footprints were plotted separately. It is shown that in general, these two different luminaires produced measurable illumination over the 270 ft spacing. Both the HPS and plasma luminaires produced oval-shaped lighted areas. The footprints peak right below the luminaires. However, the lighted area produced by the 400 W HPS luminaires is much greater than that by the 295 W plasma luminaires. Approximately 71% of the lighted area was covered with 0.20 foot-candles or greater with the
HPS luminaire and only 49% of the lighted area was covered with 0.20 foot-candles or greater with the plasma luminaire. In addition, the HPS luminaire produced greater illuminance than the plasma luminaire. In zone 5, a total of 40 measurements were taken around the high mast light pole. The illuminance measuring started from the HM pole and ended at the edge of roadside ditches as illustrated in Fig. 7. Fig. 8 shows the illuminance measurements in foot-candles taken in the eight radial directions of the high mast tower lighting. The W-E line indicates the illuminance measurements taken in both the west and east directions, respectively. The N-S line indicates the illuminance measurements taken in both the north and south directions, respectively. The NE-SW line indicates the illuminance measurements taken in both the northeast and southwest directions, respectively. The NWSE line indicates the illuminance measurements taken in both the northwest and southeast directions, respectively. Two major observations can be made through careful
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Fig. 6 e Illuminance footprints in zone 4 (pole #15) (Note: LML is lane marking on left, LMR is lane marking on right). (a) 400 W HPS measured in shoulder. (b) 400 W HPS measured in driveway. (c) Stray light Tesla II 295 W plasma measured in shoulder. (d) Stray light Tesla II 295 W plasma measured in driveway.
inspections of these illuminance curves. First, both types of luminaires produced a symmetrically lighted, circular area with relatively large foot-candles. The illuminance measurements of at least 0.20 foot-candles covered 100% of the lighted area with both the HPS and SoLtice LED luminaires. Second, the light illuminance produced by the 1000 W HPS luminaires was much greater than that by the SoLtice 392 W luminaires.
5.
Performance evaluation
The average maintained horizontal illuminance and uniformity ratio are the two key design values for implementing roadway lightings. Tables 3 and 4 present the road surface classifications and the roadway illuminance design values
specified by AASHTO (2005). Three design indicators are recommended in the AASHTO standard, including average maintained illuminance, minimum illuminance, and uniformity ratio. The average maintained horizontal illuminance is the average level of horizontal illuminance on the pavement area of calculation or measurement. For straight roadways, the area should cover one luminaire cycle, which is defined as the area between two poles along one side of the roadway. Uniformity ratio is defined as the ratio of average illuminance to the minimum illuminance in the area. Lower uniformity ratio indicates less frequent contrasts on the lighted roadway segments so that road users can perceive roadway conditions continuously with less discomforts. However, if the uniformity ratio is too low when the brightness is low, the visibility could be reduced, making it difficult for drivers to distinguish objects and roadway features.
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Fig. 7 e Field measurement points in test zone 5. According to the types of pavements and roadways, zones 1, 2 and 3 are classified as R2 surface on other principal arterials of intermediate land use, and zone 4 as R2 surface on interstate of intermediate land use. Because the high mast luminaires serve as interchange lighting, zone 5 does not fit into any of the AASHTO roadway lighting categories. Based on the AASHTO recommendations from Tables 3 and 4, the illuminance values used for evaluation of the lighting zones are summarized in Table 5. Presented in Table 6 are the measured illuminance metrics for the five zones. In order to evaluate the performance of the tested luminaires, the measured illuminance values and uniformity ratios of the new types of luminaries are compared with those of the HPS luminaires as well as with the recommended values in Table 5. The measured illuminance values and uniformity ratios of the luminaires in zone 1 are plotted in Fig. 9. As shown in Table 5, the recommended minimum average maintained illuminance is 1.2 foot-candles and the maximum uniformity ratio is 3. The measured average illuminance values are 1.00, 1.20, 0.87, and 0.80 foot-candles for HPS, GE LED, Philips LED, and Horner LED, respectively. Only GE LED met the AASHTO recommended for average illuminance. Each of the three types of LED luminaires produced a maximum illuminance greater than that by the HPS. The HPS had the lowest
uniformity ratio (5.8) followed by Philips LED (5.9). Therefore, in terms of average illuminance, the GE LED luminaires appear to be the best type of luminaires to replace HPS even though their high uniformity ratios are not desirable. Fig. 10 illustrates the measured illuminance values and uniformity ratios of the luminaires in zone 2. Same as zone 1, the recommended minimum average maintained illuminance is 1.2 foot-candles and the maximum uniformity ratio is 3 for zone 2. The measured average illuminance values are 1.33, 1.00, 0.89, and 0.82 foot-candles for HPS, GE LED, Philips LED, and Horner LED, respectively. As can be seen, the minimum, maximum and average illuminance values produced by the HPS are greater than those by the three types of LEDs in zone 2. In addition, the HPS's uniformity ratio is the lowest. Therefore, the HPS luminaires performed better than all these types of LEDs under the conditions in zone 2. Fig. 11 illustrates the measured illuminance values and uniformity ratios of the luminaires in zone 3. Same as the first two zones, the recommended minimum average maintained illuminance is 1.2 foot-candles and the maximum uniformity ratio is 3. The measured average illuminance values are 0.63, 0.50, 1.11, 0.84, and 0.55 footcandles for HPS, EcoLuminator induction, GE LED, Philips LED, and Metal Halide, respectively. Although none of the
Fig. 8 e High mast lighting illuminance distributions in zone 5. (a) Six 1000 W HPS luminaires. (b) Six SoLtice 392 W LED luminaires.
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Table 3 e AASHTO road surface classifications. Class
Mean luminance coefficient (Q0)
Description
R1
0.10
R2
0.07
R3
0.07
R4
0.08
Portland cement concrete road surface. Asphalt road surface with a minimum of 12% of the aggregates composed of artificial brightener aggregates. Asphalt road surface with an aggregate composed of minimum 60% gravel. Asphalt road surface with 10%e15% artificial brightener in aggregate mix. Asphalt road surface with dark aggregates; rough texture after some months of use. Asphalt road surface with very smooth texture.
Mode of reflectance Mostly diffuse
Mixed (diffuse and specular)
Slightly specular Mostly specular
Table 4 e AASHTO illuminance design values for continuous roadway lighting. Roadway classification
Principal arterials - interstate and other freeways Principal arterials - others
Minor arterials
Collectors
Local
General land use
Commercial Intermediate Residential Commercial Intermediate Residential Commercial Intermediate Residential Commercial Intermediate Residential Commercial Intermediate Residential
Average maintained illuminance (fc) R1
R2
R3
R4
0.6 to 1.1 0.6 to 0.9 0.6 to 0.8 1.1 0.8 0.6 0.9 0.8 0.5 0.8 0.6 0.4 0.6 0.5 0.3
0.6 to 1.1 0.6 to 0.9 0.6 to 0.8 1.6 1.2 0.8 1.4 1.0 0.7 1.1 0.8 0.6 0.8 0.7 0.4
0.6 to 1.1 0.6 to 0.9 0.6 to 0.8 1.6 1.2 0.8 1.4 1.0 0.7 1.1 0.8 0.6 0.8 0.7 0.4
0.6 to 1.1 0.6 to 0.9 0.6 to 0.8 1.4 1.0 0.8 1.0 0.9 0.7 0.9 0.8 0.5 0.8 0.6 0.4
Table 5 e Recommended values of illuminance performance evaluation. Zone
1 2 3 4 5
Minimum average Minimum Maximum maintained illuminance illuminance uniformity (foot-candle) ratio 1.2 1.2 1.2 0.6 to 0.9 N/A
N/A N/A N/A 0.2 N/A
3 3 3 3 or 4 N/A
luminaires had illuminance higher than 1.20, GE LED provided the highest illuminance value of 1.11. The illuminance values of the induction luminaires and the metal halide luminaires are relatively low. As Table 5 shows, the AASHTO recommended minimum average illuminance, minimum illuminance, and uniformity ratio for zone 4 are 0.6e0.9 foot-candles, 0.2 foot-candles, and 3e4, respectively. Fig. 12 illustrates the measured illuminance values and uniformity ratios of the luminaires in zone 4. Both HPS and Plasma luminaires satisfy minimum average maintained illuminance requirement, but not the minimum illuminance requirement. The uniformity ratios of the two types of luminaires are greater than the recommended value. The performance of the HPS
Minimum illuminance
Uniformity ratio
0.2 0.2 0.2 As uniformity ratio allows
3 or 4 3 or 4 3 or 4 3 3 3 4 4 4 4 4 4 6 6 6
luminaires is better than that of the Plasma luminaires in terms of the minimum average illuminance, minimum illuminance, and uniformity ratio. However, it should be pointed out that the power of the Plasma luminaires (295 W) is much lower than that of the HPS luminaires (400 W). Therefore, the electricity consumption should be considered in the life cycle cost analysis of different types of lighting devices (Jiang et al., 2015). As shown in Table 6 and Fig. 13, in zone 5, the minimum, maximum and average illuminance values produced by the 392 W tech LED luminaires are much smaller than those by the 1000 W HPS luminaires. However, the illuminance uniformity ratio with the tech LED luminaires is smaller than that with the HPS luminaires. Because of the great difference between the powers of the two types of luminaires, the LED luminaires saved a great deal of electricity.
6.
Conclusions
Through a field study of various types of luminaires, the performances of the luminaires were evaluated and compared to the HPS luminaires. Compared to HPS 250 W luminaires, both the GE 258 W and Philips 270 W LED luminaires produced similar minimum illuminance and the Horner LED and
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Table 6 e Measured illuminance metrics in different test zones. Zone
1
2
3
4 5
Luminaire type
HPS (250W) GE LED (258W) Philips LED (270W) Horner LED (200W) HPS (250W) GE LED (258W) Philips LED (270W) Horner LED (200W) HPS (250W) EcoLuminator induction (200W) GE LED (258W) Philips LED (270W) Metal Halide (320W) HPS (400W) Stray light plasma (295W) HPS (6 1000W) Global tech LED (6 392W)
Illuminance (foot-candle)
Uniformity ratio
Min
Max
Avg
0.17 0.16 0.15 0.10 0.15 0.08 0.09 0.04 0.07 0.02 0.15 0.09 0.08 0.14 0.04 0.66 0.26
3.25 4.03 3.67 4.42 5.15 3.62 3.66 4.42 2.15 2.70 3.87 3.61 1.94 3.86 3.52 5.05 1.53
1.00 1.20 0.87 0.80 1.33 1.00 0.89 0.82 0.63 0.50 1.11 0.84 0.55 1.00 0.77 2.88 0.80
5.8 7.6 5.9 8.2 8.8 12.8 10.2 19.1 9.0 22.7 7.6 9.2 6.6 7.1 21.9 4.4 3.1
Fig. 9 e Illuminances and uniformity ratios of luminaires in zone 1. (a) Illuminances. (b) Uniformity ratios.
EcoLuminator induction 200 W luminaires produced smaller minimum illuminance. The maximum illuminance values produced by these LED and induction luminaires are all greater than that by the HPS 250 W luminaires. The GE LED produced the greatest average illuminance and the Horner LED produced the smallest average illuminance. The illuminance uniformity ratio of the Philips LED is slightly better than that of HPS 250 W. The illuminance uniformity ratio of the GE LED luminaires is slightly greater than that of the HPS 250 W. The illuminance uniformity ratios of the Horner LED and EcoLuminator induction luminaires are much greater than those of the GE LED, Philips LED and HPS luminaires.
Compared to HPS 400 W luminaires, the LED and plasma luminaires produced smaller minimum, maximum and average illuminance values. The illuminance uniformity ratios of the LED and plasma luminaires are greater than those of the HPS luminaires. The GE and Philips LED luminaires produced greater average illuminance and smaller illuminance ratio values than the Horner LED and Stray light plasma luminaires. For high mast lighting, the SoLtice 392 E LED luminaires produced smaller illuminance levels but better uniformity than the HPS 1000 W luminaires. Taking into account the light performance presented in this paper, it is recommended that the LED lighting
Fig. 10 e Illuminances and uniformity ratios of luminaires in zone 2. (a) Illuminances. (b) Uniformity ratios.
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Fig. 11 e Illuminances and uniformity ratios of luminaires in zone 3. (a) Illuminances. (b) Uniformity ratios.
Fig. 12 e Illuminances and uniformity ratios of luminaires in zone 4. (a) Illuminances. (b) Uniformity ratios.
Fig. 13 e Illuminances and uniformity ratios of luminaires in zone 5. (a) Illuminances. (b) Uniformity ratios.
technologies be adopted for roadway lighting applications. In particularly, the GE 258 W, Philips 270 W, and Horner 200 W LED luminaires may be used to replace the HPS 250 W luminaires with the existing lighting poles. The GE 258 W and Philips 270 W LED luminaires may also be used to replace the HPS 400 W luminaires. The SoLtice LED 392 W luminaires may be used to replace the HPS 1000 W luminaires in high mast lightings. The potential concern associated with use of the new lighting is the light uniformity. It is recommended that further efforts be made by manufacturers to enhance the light uniformity for roadway lighting applications with the existing lighting poles. Field application data on the long-term performance and reliability is still needed for future revision of the design criteria for the new lighting technologies.
Conflicts of interest The authors do not have any conflict of interest with other entities or researchers.
Acknowledgments This work was supported in part by the Joint Transportation Research Program administered by the Indiana Department of Transportation (INDOT) and Purdue University. The authors would like to thank the study advisory committee members, Bill Smith, Todd Shields, Dana Plattner, and Ting Nahrwold of
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INDOT and Karen Stippich (FHWA) for their guidance and expertise. Sincere thanks are extended to Monty Wilson and Alan Sosbe and their crew members for their help and support in field installation and traffic control. The authors recognize the assistance provided by Tony Johnson, Harry Greer, Patrick Weaver, Maurice Hendrix, Hobert Deaton, and Robert White in field light testing.
references
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Jiang, Y., Li, S., Guan, B., et al., 2015. Cost effectiveness of new roadway lighting systems. Journal of Traffic and Transportation Engineering (English Edition) 2 (3), 158e166. LSC, 2017. How Do Metal Halide Lamps Work? Available at: http:// www.lrc.rpi.edu/programs/nlpip/lightingAnswers/mwmhl/ work.asp (Accessed 12 December 2017). Moreno, I., Sun, C., 2008. Modeling the radiation pattern of LEDs. Optics Express 16 (3), 1808e1819. Philips, 2017. LED Lighting. Available at: http://www.lighting. philips.com/main/education/led-lighting (Accessed 12 December 2017). Plasma Globe, 2018. Available at: http://en.wikipedia.org/wiki/ plasma_globe (Accessed 19 July 2018). USDOE, 2010. High-Intensity Discharge Lamps: Analysis of Potential Energy Savings. Energy Efficiency Program for Commercial and Industrial Equipment. EE-det-03-001. U.S. Department of Energy (USDOE), Washington DC.
Dr. Yi Jiang received his Bachelor degree in civil engineering from Tongji University in China. He received his Master's and PhD degrees in civil engineering from Purdue University in the USA. He worked in the Indiana Department of Transportation as a highway engineer and section manager before joining the faculty at Purdue University. Dr. Jiang is a full professor in the Department of Building Construction Management at Purdue University.