National Academies Press: OpenBook

Airport Parking Garage Lighting Solutions (2015)

Chapter: Chapter 3 - Designing for Lighting Performance

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Suggested Citation:"Chapter 3 - Designing for Lighting Performance." National Academies of Sciences, Engineering, and Medicine. 2015. Airport Parking Garage Lighting Solutions. Washington, DC: The National Academies Press. doi: 10.17226/22180.
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Suggested Citation:"Chapter 3 - Designing for Lighting Performance." National Academies of Sciences, Engineering, and Medicine. 2015. Airport Parking Garage Lighting Solutions. Washington, DC: The National Academies Press. doi: 10.17226/22180.
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Suggested Citation:"Chapter 3 - Designing for Lighting Performance." National Academies of Sciences, Engineering, and Medicine. 2015. Airport Parking Garage Lighting Solutions. Washington, DC: The National Academies Press. doi: 10.17226/22180.
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Suggested Citation:"Chapter 3 - Designing for Lighting Performance." National Academies of Sciences, Engineering, and Medicine. 2015. Airport Parking Garage Lighting Solutions. Washington, DC: The National Academies Press. doi: 10.17226/22180.
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Suggested Citation:"Chapter 3 - Designing for Lighting Performance." National Academies of Sciences, Engineering, and Medicine. 2015. Airport Parking Garage Lighting Solutions. Washington, DC: The National Academies Press. doi: 10.17226/22180.
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Suggested Citation:"Chapter 3 - Designing for Lighting Performance." National Academies of Sciences, Engineering, and Medicine. 2015. Airport Parking Garage Lighting Solutions. Washington, DC: The National Academies Press. doi: 10.17226/22180.
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Suggested Citation:"Chapter 3 - Designing for Lighting Performance." National Academies of Sciences, Engineering, and Medicine. 2015. Airport Parking Garage Lighting Solutions. Washington, DC: The National Academies Press. doi: 10.17226/22180.
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Suggested Citation:"Chapter 3 - Designing for Lighting Performance." National Academies of Sciences, Engineering, and Medicine. 2015. Airport Parking Garage Lighting Solutions. Washington, DC: The National Academies Press. doi: 10.17226/22180.
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Suggested Citation:"Chapter 3 - Designing for Lighting Performance." National Academies of Sciences, Engineering, and Medicine. 2015. Airport Parking Garage Lighting Solutions. Washington, DC: The National Academies Press. doi: 10.17226/22180.
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Suggested Citation:"Chapter 3 - Designing for Lighting Performance." National Academies of Sciences, Engineering, and Medicine. 2015. Airport Parking Garage Lighting Solutions. Washington, DC: The National Academies Press. doi: 10.17226/22180.
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Suggested Citation:"Chapter 3 - Designing for Lighting Performance." National Academies of Sciences, Engineering, and Medicine. 2015. Airport Parking Garage Lighting Solutions. Washington, DC: The National Academies Press. doi: 10.17226/22180.
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Suggested Citation:"Chapter 3 - Designing for Lighting Performance." National Academies of Sciences, Engineering, and Medicine. 2015. Airport Parking Garage Lighting Solutions. Washington, DC: The National Academies Press. doi: 10.17226/22180.
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Suggested Citation:"Chapter 3 - Designing for Lighting Performance." National Academies of Sciences, Engineering, and Medicine. 2015. Airport Parking Garage Lighting Solutions. Washington, DC: The National Academies Press. doi: 10.17226/22180.
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Suggested Citation:"Chapter 3 - Designing for Lighting Performance." National Academies of Sciences, Engineering, and Medicine. 2015. Airport Parking Garage Lighting Solutions. Washington, DC: The National Academies Press. doi: 10.17226/22180.
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14 There are several sources of recommendations and guidelines for lighting design and evaluation. The IES Lighting Handbook, 10th Edition, provides lighting requirements for a parking garage. Similarly, IES RP-20, “Recommended Practice for Parking Facilities,” provides additional infor- mation for the designer in terms of lighting levels and maintenance. The IES G-1, “Guideline for Security Lighting,” contains more information relevant to garage lighting. The newer IES Light- ing Handbook, discussed below, covers parking garage lighting as well. None of these documents, however, is specific to airport parking garages. This guidebook chapter covers some of the existing guidelines, their application to airport parking garages, current lighting practices, airport garage user feedback on garage lighting, and some methodologies for determining the lighting needs in airport parking garages. It also gives recommendations for airport garage lighting stemming from existing standards and the state of the industry. 3.1 Design Standards 3.1.1 IESNA RP-20 The IES recommends practices for lighting various types of spaces; the 1998 IES Recom- mended Practice for Lighting of Parking Facilities (RP-20) provides guidance on the required lighting levels for parking garages. IESNA RP-20 highlights the potential for vehicle-to- pedestrian conflict, the need for security, and the importance of the entrance and exit ramps as the basis of its lighting design recommendations. These recommendations, taken from Table 2 of RP-20, are shown here in Table 9. The IESNA RP-20 recommendations cover horizontal and vertical luminance. IESNA RP-20 also recommends using daylighting to achieve the higher light levels required at the entrance and exits to the garage. It recommends uniformity levels, defined as the ratio of maximum light level to the minimum light level. It also covers highlighting special areas in the garage with different lighting levels, and different lighting for entrances during the night and day to aid in transition- ing. Illuminance, luminance, uniformity, and highlighting will be covered in more detail in the next subsection. 3.1.2 IES Lighting Handbook A more recent publication by the IES, the Lighting Handbook (DiLaura et al., 2011), provides guidance for lighting parking garages beyond that in the IESNA RP-20. The Lighting Handbook guidance establishes the horizontal and vertical illuminance criteria based on tasks in the space. While specific values are not provided, the Lighting Handbook C H A P T E R 3 Designing for Lighting Performance

Designing for Lighting Performance 15 recommends that garage designers should make illuminance selections based on the follow- ing steps: • Create a system for determining which areas have lighting with what illuminance level. Sec- tion 4.12 of the Lighting Handbook suggests designers categorize the space based on lighting need, with Category A for 1 lx, up to Category K, for 50 lx. • Link each activity with an illuminance category. Activities may be associated with the differ- ent locations within the parking area, such as ramps and elevators, or they could be based on a task survey. • Evaluate observers’ ages. Three categories of age are considered in the Lighting Handbook: (1) at least 50% of the observers are less than 25 years old, (2) 50% of observers are between 25 and 65, and (3) at least 50% of the observers are above 65. Because light perception changes with age, the age categories are associated with illuminance target values; Category 1 has the lowest target value, and Category 3 has the highest. • Determine the appropriate horizontal and vertical illuminance target values. Different areas, activities, and age groups will require different horizontal and vertical illuminances. • Determine the design metrics, including average, minimum, and maximum, as well as uni- formities. Average-to-minimum and maximum-to-minimum present the lower bound and upper bound for illuminance uniformities. The upper limit for parking decks should not exceed 10-to-1. • Account for mesopic multipliers (discussed later in this document) to ensure they are appro- priate. The mesopic adaptation state should be assessed to determine if observers are likely to experience it. After obtaining the multipliers, adjust the illuminance criteria. A detailed example can be found at Table 26.6 in the Lighting Handbook. • Finalize recommended nighttime and daytime illuminance. Itemize nighttime and daytime horizontal and vertical illuminance as well as uniformity criteria. In general, nighttime illumi- nances, the baseline illuminance condition, are consistent for different locations such as drive aisles, parking bays, ramps, and entries. Daytime illuminances are consistent with the baseline condition only for drive aisles and parking bays. Ramps and corners should be designed to have illuminance of two times the baseline condition. Entries and exits require illuminance of 10 times the baseline condition. Finally, the Lighting Handbook provides guidance on accent lighting. Parking garage users are interested in finding some locations, such as elevators and stairs, very easily, and accent lighting can help. Table 15.2 in the Lighting Handbook (DiLaura et al., 2011) can help define accenting criteria. Current practice in airport garage lighting follows this suggestion. In many Garage Section Recommended Minimum Vertical Illuminance (lx) Recommended Minimum Horizontal Illuminance (lx) Recommended Minimum Uniformity Ratio of Horizontal Illuminance (Maximum lx:Minimum lx) Basic 5 10 10:1 Ramps – Day 10 20 10:1 Ramps – Night 5 10 10:1 Entrances – Day 250 500 Entrances – Night 5 10 10:1 Stairways 10 20 Source: Data from IESNA RP-20, 1998, Table 2, compiled by VTTI Table 9. Recommended lighting design values in parking garages.

16 Airport Parking Garage Lighting Solutions cases, 10× lighting is used to highlight important areas in airport garages, but inefficient incan- descent luminaires are often used, which presents an opportunity for lighting designers to reduce operating costs. The IES Lighting Handbook is a complicated document that requires significant cross- referencing with cumbersome criteria. The next IES RP-20 is expected to incorporate guidelines similar to those in the Lighting Handbook; however, the guidelines will be simplified and clarified for ease of use. 3.1.3 APTA Recommended Practices Another source of recommendations for parking garage lighting is the APTA Recommended Practice for Security Lighting for Transit Passenger Facilities (APTA, 2009). APTA recommends continuous lighting for parking garages. Its recommendations for lighting levels are shown in Table 10 here, taken from tables 6 and 7 in the APTA document. APTA recommends significantly higher lighting levels than the IES RP-20 (about 60 lx versus 10). The APTA document does not provide additional recommendations for lighting in special areas or enhanced work spaces. The APTA document referenced patron safety and security; that is likely the reason their document has higher recommended lighting levels than the RP-20. 3.1.4 City Codes In addition to the recommended lighting criteria, some local authorities provide regulations for parking garage lighting. For example, the City of Santa Barbara, California, regulates garage- lighting design to enhance the lighting quality and energy use. The regulations also reduce the potential for light pollution, glare, light trespass, and wasted energy caused by deficient lighting design and misdirected light (SOTCOSB, 2009). The following goals and guidelines are excerpted from the Santa Barbara regulation: Goals • A safe transition from garage interior to the exterior area and vice versa during both daytime and nighttime is required. • Minimum lighting for safety, security, and uniformity must be provided. Higher lighting levels may be approved by the Design Review Boards for additional safety and security. • Selection of fixture type, lighting technology, location, and control of lighting level should be conducted in a way to optimize energy consumption. Garage Section Minimum Recommended Illuminance (lx) Averaged Recommended Illuminance (lx) Horizontal Maintained Vertical Maintained Horizontal Initial Vertical Initial Maintained Initial Open parking lots 11 5.4 15 7.5 32 46 Parking garages 16 8.6 24 13 65 97 Source: Data from APTA Recommended Practice for Security Lighting for Transit Passenger Facilities, 2009, Table 7, compiled by VTTI Table 10. Recommended lighting design values in parking garages.

Designing for Lighting Performance 17 • Title 24 Lighting Standards need to be met. [Title 24 is an energy regulation specific to California]. Guidelines • Acceptable lighting technologies that meet the guidelines are HPS and fluorescent. Deluxe HPS lamps are also recommended because of their high color rendering ability. MH lighting is not recommended and is not permitted in the transition section or on roof-level pole-top fixtures. LED and induction lighting may be eligible where warm color quality is desired. • Transition sections, for both drivers and pedestrians, must extend 60 ft into the building from its exterior face. Illuminance at the transition sections must be controlled according to the difference between the lighting level of the interior and the exterior, which varies by the time of day; sunlight, moonlight, and street lighting all affect the exterior illuminance. • The brightness of the garage interior must be evaluated. Directed task lighting is preferred over higher general illumination. • Glare from directly viewing the light sources can be an issue when the light sources are visible from outside the building, so fixtures must then be carefully placed and/or shielded. • On roof parking levels, pole-top fixtures should be cutoff fixtures. Other factors to be considered are minimizing pole height and avoiding placing the poles at the perimeter of the building. • Metal halide lighting is not recommended, but if used in the garage interior, the color of the walls should warm the reflected light. • When using HID lighting, cutoff fixtures with horizontal lamp mounting and flat glass lenses are preferred. “Sag” or “drop” lenses are not allowed because they lead to excessive glare. • For better energy conservation, additional lighting controls for garage interior lighting are recommended to control the lighting according to need. • Average horizontal illuminance at ground level should be aimed at one foot-candle (fc) and should not exceed 1.5 fc. Where needed and approved by the Design Review Boards, higher values can be approved for additional safety and security. • A foot-candle plot that illustrates illuminance levels at the transition zones, up to the furthest floor area visible from the vehicle entrance or exit, must be presented. Minimum, average, and maximum foot-candles and the uniformity ratio must be calculated. Illuminance should not be more than the ambient street lighting level at 10 ft beyond the vehicle entrance or exit. • Sufficient plan, detail, section, and finish information need to be included in plans submitted to the Design Review Board, so they can determine whether or not the plans adhere to the guidelines. These guidelines include a plan-review checklist to facilitate lighting design meeting the requirements. 3.2 Lighting Standards and Recommendations for Airport Garages The following guidance was developed assuming a medium dark concrete surface. Adjust- ments will need to be made for different pavement surfaces as recommended in the Building Design Considerations chapter. 3.2.1 Illuminance Level Horizontal illuminance. The authors of this guide found that airport garages tend to have higher average horizontal illuminances than the values suggested by RP-20, ranging from 30–100 lx in the interior parking levels, whereas the minimum levels suggested by RP-20 are 10 lx for basic areas and bays at night, and 20 lx for ramps and stairways. Since these are

18 Airport Parking Garage Lighting Solutions the minimums, an assumption needs to be made about uniformity to determine the aver- age values suggested by RP-20. If one assumes 2:1 uniformity, which would be difficult to achieve in practice for reasonable cost, then the maximum illuminance would be 20 lx and the average would be 15 lx. With a maximum uniformity ratio of 10:1, the average rises to 55 lx. Therefore, current practice is to illuminate at a horizontal illuminance approximately two times RP-20. The higher levels of illumination could be because lighting design for airport garages is more security-focused than that for other garage types. Discussions with some personnel involved in airport garage lighting indicated that the higher lighting levels were driven by a concern for patron safety. Additionally, a survey of airport garage patrons found that they agree that they begin to feel comfortable (Figure 15) and safe (Figure 16) beginning at an average horizontal illuminance of ~35 lx; and strongly agree that they feel comfortable and safe by 40 lx, while not 0 1 2 3 4 5 6 200 40 60 80 100 120 Re sp on se : 1 = d is ag re e to 5 = a gr ee Illuminance (lx) Q03 Responses (1-5) vs. Horiz Illum (lx) Figure 15. Q03—feeling of comfort at horizontal illuminance levels. Source: VTTI Analysis. 0 1 2 3 4 5 6 0 20 40 60 80 100 120 Re sp on se : 1 = d is ag re e to 5 = a gr ee Illuminance (lx) Q05 Responses (1-5) vs. Horiz Illum (lx) Figure 16. Q05—feeling safe at horizontal illuminance levels. Source: VTTI Analysis.

Designing for Lighting Performance 19 experiencing significant glare. However, beyond an average vertical illuminance of 40 lx, there is little increase in comfort or feeling of safety. These data do not determine how little average horizontal illuminance is needed for a neutral or negative response to either feeling safe or comfortable. The conclusion drawn here is that the RP-20 guidelines may not be ideal for airport garages. For safety and security, an average horizontal illuminance of 40 lx is recommended for general (not highlighted) airport garage areas. Recommendation: Airport garage bays and general areas should have a minimum average horizontal illuminance of 40 lx to maximize patron comfort without expending excess capital, equipment, or power. Vertical illuminance. Vertical illuminance recommendations are directed at pedestrian safety because it highlights vertical surfaces and helps drivers detect and recognize pedestrians. The RP-20 guidelines for vertical illuminance are 5 lx in general areas at night, and 10 lx in stairways. This is about half of the recommended horizontal illuminance. In practice, average verti- cal illuminance levels found in airport garages were higher, roughly proportional to the horizontal illuminance. However, it was found that vertical illuminance was less critical than horizontal illu- minance when it comes to patron comfort and safety (Figure 17). Therefore, a minimum average vertical illuminance is not required. Vertical-to-horizontal illuminance ratio. The RP-20 guidelines recommend a vertical-to- horizontal illuminance ratio of 1:2. In practice, airport garages tend to have lower vertical-to- horizontal illuminance ratios. In many garages, the ratio was closer to 1:1. This may be because airport garage lighting designs use fewer wider-angle luminaires to reduce installation and capi- tal costs. High vertical illumination levels can cause glare, and luminaire spacing with a large off- set can exacerbate the problem of shadows near vehicles. Research shows that there appears to be a correlation between the illuminance ratio and perceived glare (Figure 18) and that most of the LED lamps were perceived as more glaring than other lighting technologies at the same ratios. The two outliers and the one other marked data point are LED installations. As described in the technology section, LED sources are very small and utilize different optics for spreading the light out, resulting in a higher chance of glare. See the section on glare later in this chapter. R² = 0.0258 0 1 2 3 4 5 6 0 20 40 60 80 100 120 Re sp on se : 1 =d is ag re e to 5 =a gr ee Illuminance (lx) Q03 Responses (1-5) vs. Vert Illum (lux) Figure 17. Feelings of comfort at vertical illuminance levels. Source: VTTI Analysis.

20 Airport Parking Garage Lighting Solutions Recommendation: Airport garage lighting should strive for 1:2 vertical-to-horizontal illumi- nance ratio from RP-20, but LED installations should strive for 1:3–1:2 vertical-to-horizontal illuminance ratio. These illuminance recommendations are for general areas. Recommendations for highlighted areas within an airport garage, like ramps, toll areas, entrances and exits, and cross walks are covered in a subsequent section. 3.2.2 Emergency Lighting According to RP-20, if there is a power outage, a low-level lighting system is required to provide safety and security in the parking facility. The emergency lighting system should pro- vide 10% of the light of the normal system, and at least 10 lx along the path of egress. This lighting system should meet the requirements of National Fire Protection Association (NFPA) 101 Life Safety Code and the emergency system requirements of NFPA 70 National Electrical Code. IES RP-20 does not specifically mention airports or activities that might require special atten- tion during the lighting design process. Airport garage safety requirements mirror those of other garage types, so the RP-20 guidelines are recommended. Recommendation: Emergency lighting should provide 10% of the lighting level of the regular garage lighting system and provide 10 lx along the paths of egress. 3.2.3 Luminance Luminance, the light reflected from surfaces, drives roadway visibility. Luminance depends both on illuminance level and the reflectivity of the road surface. Common standards (RP-8, RP-20, the Lighting Handbook) list reflectance values or rules of thumb. In general, darker pavement requires more lighting. Painting a surface can increase its luminance by increasing its reflectivity, but glossy paints can be so reflective that they cause glare. Painted surfaces require maintenance, and paint on road surfaces requires maintenance on a short timeline, possibly annually. One solution is to stain concrete with a color that 0 0.5 1 1.5 2 2.5 3 0 0.2 0.4 0.6 0.8 1 1.2 1.4 Re sp on se :1 =d is ag re e to 5= ag re e Vert. to Hor. Ra o (no units) Q09 Responses (1-5) vs. Vert. to Hor. Illum. Rao Figure 18. Glare response versus ratio of horizontal illuminance to vertical illuminance. The blue line is the trend of glare assessment. The marked data points are LED sources. Source: VTTI Analysis.

Designing for Lighting Performance 21 will reflect light in the amount and wavelength (i.e., warm, cool) desired. From the Lighting Handbook: Surface reflectances and accenting: Specific light reflectance values (LRVs) are recommended for col- umns, walls, and ceilings (particularly adjacent to the ramps, corners, entries, and exits) with and without color accent as a guiding tool. As a result, luminances and overall perception can be improved. High LRVs result in improved vertical and horizontal illuminance, reduced glare, better user perception, and other benefits. Recommendation: When designing and upgrading lighting systems for airport garages, take into account the effect of the color and material of the walls and road on luminance and color temperature. 3.2.4 Uniformity This metric, expressed as the average:minimum illuminance ratio or the maximum:minimum illuminance ratio, is used to quantify the impact of areas with minimal light levels, such as dark shadows between vehicles in airport garages. Low uniformity can indicate both uncomfortably bright and awkwardly dim areas. When light is very uniform, however, few shadows are cast, reducing the contrast of a vertically illuminated object or pedestrian. Thus, high uniformity (low contrast) can hinder detection and recognition. A survey of airport garage patrons found little link between lighting uniformity and patron comfort, so it is possible that if lighting uniformity is between the above extremes, the effect of lighting on patron experience is small. Most airport garages have continuously high vehicle occupancy. A significant portion of those vehicles is tall sport-utility vehicles (SUVs) and pickup trucks. Those vehicles cast dark shadows that have a significant effect on minimum light levels, especially in-between vehicles (see Figure 19). Even if garage lighting guidelines are met, the light level near vehicles can dip below 1 lx. When these low levels are compared to the average or peak values, the uniformity ratios are considerably higher than those suggested by RP-20 (10:1 maximum:minimum hori- zontal illuminance levels). Airport garage lighting design should take into consideration shad- ows produced by a garage full of tall vehicles and strive to provide minimum recommended lighting levels between vehicles. Recommendation: Follow the RP-20 guidelines for minimum horizontal uniformity (i.e., 10:1 maximum:minimum), but take the presence of parked SUVs into account. Figure 19. Shadows cast by tall SUVs. Source: VTTI.

22 Airport Parking Garage Lighting Solutions 3.2.5 Color Contrast Recent studies suggest that color contrast is, like vertical illuminance, important for facial recognition and object detection. Surveys performed by the authors suggest that uniformity is important for color recognition. At this time, no recommendations stem from this exploratory research. 3.2.6 Airport Garage Layout and Highlighting The effectiveness of parking garage lighting depends on the activities performed in the vari- ous areas of the garage. Locations with more pedestrian traffic, rental vehicles, and toll booths can be made brighter than surrounding areas to promote safety. Lighting can also be used to help guide users toward their destination, usually walkways, stairways, payment areas, airport entrance, vehicle rental, or the garage exit. Entrances and exits should have transitional lighting to prevent glare when moving into and out of the garage. Other areas can be lit to a lesser extent, saving energy. Airport garages share similarities and differences with typical garages, affecting the lighting design recommendations here. Many garages have the following areas: • Dedicated corners/ramps; • Drive aisles/parking areas; • Drop-off/pickup areas, interior vehicle transaction areas, and valet; • Elevator lobbies, pedestrian transaction area, and stairways; and • Vehicular entries and exits. Airport parking garages tend to have the following less-common areas: • Vehicle rental offices; • Baggage cart rental; and • Higher-security areas. In addition, airport parking garages tend to not be located near residential areas. Areas with pedestrian traffic. The RP-20 acknowledges the importance of highlighting stairways in a garage; while it recommends a basic horizontal illuminance of 10 lx at night, it recommends 20 lx for stairways. This is to prevent tripping, and for security. Walkways through a parking garage have different illumination requirements than those of stairways. While security and tripping are both concerns in walkways, so is making sure drivers can see pedestrians. Illuminance measurements at airport garages found huge variation in the ratio of walkway illumination to the illumination in the parking bay. In one garage, that ratio was 30:1 for horizontal illuminance and about 12:1 for vertical illuminance. In two other garages, the ratio of walkway illumination to the illumination in a nearby parking bay was between 1.5:1 and 2:1 for both horizontal and vertical illuminance. The amount of glare depends heavily on the luminaire cutoff, possibly explaining the lack of perceived glare in the garage with a 30:1 highlighting ratio. Cutoff can be creatively accomplished with a number of devices, including the garage’s structural beams. Airport patrons, on average, agreed that they felt safe and comfortable to nearly the same extent in the above garages. They also agreed that none of the above garages had glaring light- ing. Those data suggest that the highlighting ratio, between 2:1 and 10:1 or higher with cutoff, does not affect perceptions of safety or glare. The recommendation here is to follow the spirit of RP-20 with respect to highlighting walkways.

Designing for Lighting Performance 23 Recommendation: Highlight walkways and other areas with high pedestrian traffic at a ratio of at least 2:1 with respect to the basic lighting level in the garage. At ratios of above 10:1, use cutoff to prevent glare. Make sure vertical illuminance does not fall below 20 lx. Vehicle rental areas. Drivers likely unfamiliar with their vehicles and surroundings, as well as pedestrians, will be near vehicle rental offices. These areas should also be highlighted. Recommendation: Highlight vehicle rental areas at a ratio of 2:1 with respect to the basic lighting level in the garage. Ramps. Depending on the garage layout, ramps may have low sight distance and pedestrian traffic. The RP-20 suggests that, during the day, ramps be illuminated two times as brightly as the basic level in the garage. Bi-level lighting could be used on ramps to reduce costs during the night. Recommendation: Highlight ramps at a ratio of 2:1 with respect to the basic lighting level recommended in this guidebook in the garage during the day and utilize bi-level lighting at night if cost-effective. Entrances. Entrances are transition zones, and are not unique to airport garages. It is sug- gested designers of airport garage lighting follow the RP-20 recommendations for lighting entrance areas. See Table 9. Recommendation: Follow the recommendations in RP-20 for lighting airport garage entrances. Top level. The rooftop spaces on parking garages are lighted in accordance with the parking lot standard in RP-20, 2 lx for basic horizontal illuminance, and 5 lx for enhanced security. Hav- ing the horizontal illuminance on the top level match that on the other levels (recommended 40 lx) would provide a sense of continuity between levels, and could increase patrons’ feelings of safety and encourage usage of the upper decks. Recommendation: Illuminate the top level of the garage to the same level as the basic lighting in the parking bays. 3.2.7 Daylighting Like other garages, airport parking garages should take advantage of fractional daylighting and controlled lighting. The extent to which daylighting is possible largely depends on the garage’s layout, and more details about daylighting design strategies can be found in section 11.3.2.4 of the Lighting Handbook. This guide recommends daylight survey in the peripheral bays and drive lanes, as nine out of 11 peripheral airport bays surveyed had enough daylight illumination to meet RP-20 and the general recommended illumination levels in this guide (up to 50 feet from the perimeter). Daylight lighting can reach much farther, as much as three bays in from the perimeter, which is over 150 feet. Therefore, there is significant savings potential related to using bi-level lighting with daylight sensors in at least the outermost bays and drive lanes. Recommendation: Survey the outer bays and drive lanes for daylighting and to determine if daylight sensors and bi-level lighting can be used. Follow the design strategies outlined in the Lighting Handbook for daylighting in airport garages. 3.2.8 Luminaire Efficacy Efficacy is the main measure of the light produced by, and the efficiency of, a luminaire. A luminaire’s optics and reflectors significantly impact how much light it produces. Efficacy is usually calculated and reported as light loss factor (LLF).

24 Airport Parking Garage Lighting Solutions The LLF value is applied as a multiplier to achieve the maintained lighting level from the ini- tial installed level. From ANSI/IES RP-8-00 (American National Standard Practice for Roadway Lighting): LLF LLD LDD LATF LCD HE VE BF= × × × × × × where: • LLD is lamp lumen depreciation and is fixed by lamp type; for example, LEDs have an LLD of 0.70; • LDD is luminaire dirt depreciation and depends on installation environment (see Figure 20); • LATF is luminaire ambient temperature effects and differs by lamp type and local temperatures; • LCD is luminaire component depreciation; • HE is a heat extraction factor; • VE is voltage effects such as transients; and • BF is the driver and lamp factor (Ballast Factors) and includes loss of efficiency when operat- ing at off specification conditions. LLF affects cost considerations in the lighting design. For example, if the luminaires in one design have a 5% higher LLF than those in another design, the first design would require 5% more initial equipment, 5% more energy to operate, and 5% more spending on maintenance. The LLF’s impact on project cost can mean the difference between new technology insertion and continued use of legacy systems at higher energy costs. Figure 20 provides some guidance for LLF estimation, as LDD is a major component of LLF. Complicating LLF calculations is the fact that the LDD is often assumed to be equal across the luminaire output, when that is not the case. Luminaire testing found that dirt depreciation is more significant at the edges of the area of distributed light than it is directly under the luminaire, because low angles are more affected by dirt on the luminaire’s glass (the luminaire tested was a flat-lensed II Very Dirty Dirty Exposure Time in Years Lu m in ai re D irt D ep re ci a on F ac to r ( LD D) Moderate Clean Very Clean 876543210 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 Figure 20. Example chart for finding LDD based on time and environment (not for use in lighting design; for design, reference IES RP-08-00). Source: VTTI Analysis.

Designing for Lighting Performance 25 medium-throw luminaire). The testing showed that assuming a single dirt depreciation factor applies equally across the entire area of a luminaire’s light distribution is fundamentally incorrect. Recommendation: Light loss factors should be calculated for airport garage lighting designs, with special attention to dirt depreciation. 3.2.9 Glare Glare, or light that is so bright that it causes discomfort or impairs one’s ability to make out surrounding objects, impedes wayfinding and increases the chances of pedestrian-vehicle con- flict. In parking garages, drivers and pedestrians experience glare differently. Drivers are usually lower than pedestrians. Because drivers are lower than pedestrians, and because the vehicle roofs cut off light, for seated drivers to see the same light source as pedestrians, the drivers would have to be farther away from the light source. Therefore, glare is more of an issue for pedestrians in parking garages than it is for drivers, except in areas with high illumination such as entrances and ramps. A number of design constraints can introduce glare into a parking garage’s lighting. Those constraints are related to the parking garage environment, with low ceilings, helix ramps, sun- light intrusion, and the size of a lamp. As illustrated in the discussion of vertical-to-horizontal illuminance ratio, a smaller ratio of vertical-to-horizontal illuminance and location of the luminaires to utilize the garage structure as vertical cutoffs can reduce the perception of glare. Ceiling height. High capital costs tend to drive garage-lighting designers towards using fewer luminaires with a larger area of illuminance. These large-area luminaires, when mounted on typically low (7 to 9 ft) garage ceilings, throw bright light out at a shallow angle, causing glare. Therefore, glare can be a significant challenge when balancing the number of luminaires, light distribution, and cost. Recommendation: Place a great value on reducing glare in airport garages because the poten- tial for pedestrian-vehicle conflict is high. Helix ramps. Second, helix ramps are often illuminated more brightly than the surrounding garage areas. That, combined with a lack of space, means many helix ramps have luminaires on their inner walls aimed in the direction of travel. The luminaires usually do not produce glare in the drivers’ line of sight, but they can produce glare in peripheral vision. Recommendation: On helix ramps, place luminaires above vehicle level so the vehicle roof will cut off the light, or carefully shield the luminaires. Sunlight intrusion. Open sidewalls in aboveground garages allow sunlight in at various times of day. Depending on the garage layout and time of day, sunlight can cause more glare than artificial lighting, especially for those in the darker interior of the garage. To allevi- ate sunlight glare, airport garage lighting can have higher illuminance in the bays close to the edges of the garage to help patrons transition between sunlight and interior lighting. Designers could also place light-blocking or diffusing sidewalls on the east and west faces of the garage. Recommendation: Evaluate the parking garage site for sunlight intrusion. Consider the loca- tion of walkways, orientation of the garage walls, time of day, and interior illumination levels. Raise interior illuminance or block sunlight if necessary. Daylighting can be helpful if utilized correctly; see Chapter 4: Building Design Considerations.

26 Airport Parking Garage Lighting Solutions Light-source size. Some light sources, like LEDs, are very small, and appear more glar- ing than larger lamps with the same intensity. As illustrated in the vertical-to-horizontal illuminance ratio section above, LED light sources are more likely to be perceived as glaring. The unified glare rating, or UGR (CIE 117-1995—Discomfort Glare in Interior Lighting), is based on the background luminance (LB), fixture luminance (L), and the solid angle subtended by the light source (w) and the Guth position index. The Guth position index is based on two angles: a = angle from vertical of the plane containing the source and the line of sight in degrees; and b = angle between the line of sight and the line from the observer to the source. This pro- duces UGR values that range from 5 to 40, where anything at 10 or below is negligible and any- thing above 30 is unacceptably glaring. The UGR is proportional to the log (L2/LB) indicating that higher background luminance will reduce glare. Luminance is also by definition, intensity of light emitted per unit area; so a larger light source, i.e., a larger solid angle, will also have a lower luminance (L) for a given total output in lumens. Unfortunately, UGR is generally known to only be accurate for certain source sizes. It is lim- ited to source sizes between 0.0003 steradians and 0.1 steradians. This minimum corresponds approximately to the minimum of a 2-inch source (such as a standard incandescent bulb) from about 32 feet away, which is much larger than an LED source in a luminaire, so cannot be accu- rately used on LED sources. Recommendation: When using luminaires with small light sources, carefully choose the optics to reduce luminance of the source, and use cutoff and background luminance to reduce glare. Creative cutoff. Designers should use existing features to cut off potentially glaring light sources as a way to cut costs. Luminaires can be placed next to beams or other structures in the garage, cutting off the light and shielding an area from potential glare. To improve efficacy, the structure used as the cutoff should be painted or stained white to reflect as much light as possible. When reducing the glare to drivers, the driver’s height and average vehicle roof height should also be considered. Recommendation: Consider glare with respect to both drivers and pedestrians. Use the park- ing garage environment to creatively and cost-effectively cut off light and prevent glare. 3.2.10 Light Trespass Airport garages are usually located away from residences, but close to hotels and restaurants. Light trespass from an airport garage is less likely to aggravate residents, but it is more likely to aggravate travelers, potentially driving them away from the airport and businesses housed therein. There are three main concerns for light trespass with respect to airport garages: the lighting on the top level, lighting trespass from the ramps, and the lighting at the edges of the parking floors. Lighting on the top level. On the top levels of parking garages, luminaires are usually placed at 25 feet, because higher placement allows for less complicated luminaires and optics and lower cost. Depending upon the luminaire type and placement, significant light could trespass past the edge of the garage; thus trespass considerations must be balanced with cost effectiveness and achieving good uniformity and illuminance levels. Recommendation: Adjust luminaire placement and cutoff design to prevent light trespass on airport garage top levels.

Designing for Lighting Performance 27 Ramp and helix illumination. Ramps and entrances should be more brightly illuminated than other garage areas, so light trespass from these areas is more likely. In addition, exter- nal ramps, especially helix ramps, usually have minimal clearance above and to the side of the vehicles, forcing designers to place luminaires on the sidewalls, shining outward. If the helix has an open outer wall, a significant amount of light could project out of the helix at a low angle. Recommendation: On a helix ramp, either place the luminaire close to the ceiling, or raise the outer wall to prevent light trespass. Perimeter lighting of each floor. The luminaires nearest to the perimeter of the garage can create light trespass through open sidewalls. Light designers have a few options to avoid this. Luminaires with asymmetric illuminance patterns could be located near the wall and aimed toward the center of the garage. This way, any trespass light will be exiting at an angle near ver- tical, illuminating the base of the garage only. Another option would be to install light shields or additional reflectors to prevent trespass. Finally, the structure of the garage can be used to provide additional cutoff as mentioned in the glare section above. Recommendation: Use the garage structure, luminaires with asymmetric illuminance pat- terns, and light shields to prevent light trespass around the edges of the garage.

Next: Chapter 4 - Building Design Considerations »
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TRB’s Airport Cooperative Research Program (ACRP) Report 124: Airport Parking Garage Lighting Solutions provides guidance to help airport industry practitioners select the most appropriate lighting technologies for their unique parking garage conditions.

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