PARKING FACILITY LIGHTING FOR SAFETY AND SECURITY

Transcription

1 PARKING FACILITY LIGHTING FOR SAFETY AND SECURITY by Donald R. Monahan, P.E. Principal Walker Parking Consultants/Engineers, Inc South Roslyn Street, Suite 200 Englewood, Colorado (303) presented to Hawthorne Suites Hotel Charleston, SC May 23, 1996

2 Charleston, South Carolina Page 1 INTRODUCTION Monetary damages for personal injury liability claims in parking facilities often reach in the hundreds of thousands of dollars. A recent study by the American Insurance Services Group of security-related lawsuits indicated that twenty percent of the cases involved incidents in parking facilities in which the average jury award was $575,000. Even relatively minor claims for slip or trip and fall accidents can add up to nearly half a million dollars in annualized liability according to a study by WALKER of the liability claims of a large parking operator with over 1,400 parking facilities. Inadequate lighting is the factor most frequently cited in personal injury lawsuits. Adequate visibility of the slip or trip hazard or adequate lighting to deter criminal activity are the issues most often litigated. Compliance with lighting industry standards is also a factor. Lighting deficiencies with respect to any of these factors will increase the owner s risk of liability and increase monetary damages in the event of a personal injury claim. So what constitutes adequate visibility of trip hazards? How much lighting is necessary to deter criminal activity? What are the lighting industry standards? Why do so many parking structures have substandard lighting? What can be done to minimize the risk of personal injuries related to parking facility lighting? The answers to these questions follow. Armed with this knowledge, you will be able to conduct a risk assessment of your existing parking facility lighting, and recommend improvements to enhance your lighting system, if necessary. The benefits to the parking facility owner will be lower risk of personal injury liability claims as well as a reduction in the amount of monetary awards for any claims. LIGHTING TERMINOLOGY A review of lighting terminology may be necessary to enhance your understanding of this discussion. Illuminance Vertical Illuminance The quantity of light falling on a surface. The quantity of light falling on a vertical plane, surface, or object (i.e. wall).

3 Charleston, South Carolina Page 2 Horizontal Illuminance Maintained Illuminance Candela Steradian, sr Lumen Footcandle Lux Luminance Luminaire Lamp High-Intensity Discharge (HID) Lamp High Pressure Sodium Lamp Fluorescent Lamp Mercury Lamp Metal Halide Lamp The quantity of light falling on a horizontal plane, surface, or object (i.e. floor). The quantity of light that exists immediately prior to lamp replacement and fixture cleaning. The luminous intensity, in a given direction of a source that emits monochromatic radiation of frequency 540 x Hz and that has a radiant intensity in that direction of 1/683 W/sr. The solid angle subtended at the center of a sphere by an area on the surface of the sphere equal to the square of the sphere radius. The basic unit of measurement of light. A lumen equals the quantity of light passing through a one square foot opening on a sphere with a one-foot radius from a point source of one candela. The English measure of the quantity of light. One lumen falling on one square foot of surface produces illumination of one footcandle (fc). The International System (SI) unit of illumination equal to one lumen uniformly distributed over an area of one square meter. One footcandle = lux. The brightness of an object or surface. The Luminance of a surface is equal to illuminance times reflectance divided by Pi. A complete lighting unit consisting of a lamp (or lamps), together with the parts designed to distribute the light, position and protect lamps, and connect them to the power supply. The bulb or tube that provides the source of light. General term for a mercury, metal halide, or high pressure sodium lamp. A light source in which the light is primarily produced by the radiation from sodium vapor. A lamp in which the electric discharge of ultraviolet energy excites a fluorescing coating (phosphor) transforming some of that energy to visible light. A light source in which radiation from mercury vapor produces visible light. A light source in which radiation from mercury, together

4 Charleston, South Carolina Page 3 with halides of metals such as Ballast sodium and scandium, produce visible light. A device which modifies incoming voltage and current to provide the circuit conditions necessary to start and operate electric discharge lamps (fluorescent and HID). LIGHTING INDUSTRY STANDARDS The Illuminating Engineering Society of North America (IES) is generally considered the technical source for standards in the lighting industry. The IES has published a recommend practice for parking facility lighting entitled RP-20, Lighting for Parking Facilities, Their recommendations are summarized in the following table: Table 1. Recommended Maintained Horizontal Illuminances for Parking Facilities (a) Open Parking Facilities General Parking and Pedestrian Area Vehicle Use Area (only) Level of Activity Lux (Minimum on pavement) Footcandles (Minimum on pavement) Uniformity Ratio (Average/Minimum) Lux (Average on pavement) Footcandles (Average on pavement) Uniformity Ratio (Average/Minimum) High : :1 Medium : :1 Low* : :1 (b) Covered Parking Facilities (1) Day Night Areas Lux (Average on pavement)(2) Footcandles (Average on pavement)(2) Lux (Average on pavement) Footcandles (Average on Pavement) Uniformity Ratio (Average/Minimum) General parking and Pedestrian Areas Ramps and Corners Entrance Areas :1 4:1 4:1 Range of Illuminances

5 Charleston, South Carolina Page 4 Stairways Lux (1) The vertical illuminance at six feet above the pavement should also equal the values given in this table. (2) Sum of electric lighting and daylight. Footcandles Having personally testified in personal injury lawsuits allegedly due to insufficient lighting, one of the first issues addressed is whether the lighting in the vicinity of the personal injury incident met the IES standards. In order to determine compliance to IES standards, one must perform photometric measurements in accordance with IES publication LM-64, Photometric Measurements of Parking Areas. This procedure requires a light meter (photometer) with an accuracy of ±5 percent or better. A grid of measurement points must be laid out lengthwise and crosswise over the area to be evaluated. The point spacing must not exceed 10 feet for luminaires mounted 18 feet or higher, and not exceed 6 feet for luminaries mounted below 18 feet. The horizontal illuminance should be taken at each grid point with the light meter resting face up on the pavement. In addition, vertical illuminance values should be measured at a height of 6 feet above the pavement in each of three or four cardinal directions, with the lighting meter facing the perimeter walls. Depending on the time of day of the personal injury incident, lighting measurements may have to be performed both at night and during the day. Enhanced lighting levels are required at the entrances to covered parking facilities during the day to provide a transition from bright sunlight to the darker parking structure. Based on my experience with lighting measurements in over 50 parking facilities, the source of inadequate lighting is usually (1) improper selection of light loss factors in the calculation of illuminance during design, and or (2) inadequate maintenance of the lighting system. During their lifetime, the light output of lamps gradually diminishes. The lighting calculations must use the depreciated lumen output at the time the lamp is replaced, however, many designers incorrectly use the mean lumens during the life of the lamp. The result is that actual illuminance values are often 30 to 40 percent below the intended light levels. The following Table 2 indicates the recommended total light loss factors (sometimes referred to as maintenance factor) to use: Table 2. Calculation of Light Loss Factor LLD LDD LLT EF BF LLF 150W HPS

6 Charleston, South Carolina Page 5 175W MH W HO FLUOR Source: Lighting Maintenance for Safety & Profitability, PARKING Magazine, May, 1996 Therefore, if the initial light output is 10 footcandles, the light output at the end of the rated lamp life will be approximately 6 fc for 150W HPS lamps and approximately 5 fc for 175W MH lamps. Also, many lamps will burn beyond their rated life and continue to lose light output. Those lamps may only have 30 to 40 percent of their initial light output. Accumulation of dirt and bugs in the lens as well as yellowing of the lens may reduce the light output by another 30 to 40 percent. Therefore, the light output directly under the fixture should be measured at regular intervals to determine when to replace the lamp and clean the fixture (see Lighting Maintenance for Safety and Profitability in May, 1996, issue of Parking Magazine for additional information). VISIBILITY ISSUES A parking facility may not meet the IES guidelines, yet still have adequate visibility for the task related to the personal injury incident. This fact occurs because the IES guidelines are intended to cover the minimum requirements for a wide range of lighting conditions and visual tasks. Therefore, the guidelines may be excessive for the specific visual task involved in the liability claim. Slips or trips and falls represent from 50% to 75% of the liability claims in a parking facility. The first means of prevention against trips and falls is to eliminate all wheel stops, and not use curbs or islands in the parking facility design. Other means are available for channelizing cars or providing bumper protection such as pipe bollards or guardrails. For existing facilities that already have curbs that cannot be removed, the visibility of the hazard should be improved in order to minimize personnel injury claims. Visibility of trip hazards (steps, wheel stops, curbs and islands) is a function of the illuminance on the hazard and the reflectance contrast of the hazard against its background. The light reflected from a surface or object is called luminance. Luminance is calculated as follows: Luminance = Illuminance x Reflectance/Pi

7 Charleston, South Carolina Page 6 Illuminance is the amount of direct light falling on a surface, and can be measured with a light meter. The reflectance varies for different colors, and is available from paint manufacturers as illustrated in the following Table : Table 3. Reflectance of Various Colors Color Reflectance Glidden Color White 90% AC-98 Yellow 74% AC-630 Pink 53% AC-296 Grey 41% AC-516 Orange 29% AC-592 Green 20% AC-677 Brown 19% AC-595 Red 18% AC-528 Blue 11% AC-722 Purple 11% AC-749 Black 4% AC-780 Contrast is defined as the difference in luminance or brightness of the object against the background. Contrast is enhanced by painting the object such that the contrast against its background will be increased. A concrete wheel stop against a concrete floor will have minimal contrast since the object and its background will have similar reflectance. Painting the wheel stop yellow will greatly enhance the visibility. Table 4 indicates the contrast of different color combinations. The amount of contrast required for adequate visibility of an object has been researched extensively by the Roadway Lighting Committee of the Illuminating Engineering Society. The contrast at which the object can be detected 50 percent of the time by a reasonably alert young adult (age = 23) is called the threshold contrast. For a 99.9 percent probability of detecting the object, the threshold contrast should be multiplied by a factor of 2.6. The required contrast varies with the light level and age of the observer.

8 Charleston, South Carolina Page 7 Figure 1 indicates the contrast required at a 99.9 percent probability of observing a 6 inch concrete curb viewed at a distance of 20 feet. Note that the amount of contrast required increases significantly at light levels less than 2 foot candles. As some of you may know, the

9 Charleston, South Carolina Page 8 Figure 1

10 Charleston, South Carolina Page 9 Illuminating Engineering Society recommends a minimum illuminance of 1.25 footcandles, which is fairly consistent with these calculations. How does this information translate to the visibility of wheel stops or curbs? By manipulation of the visibility formula, one can derive the reflectance value required for the wheel stop or curb. This calculation is illustrated in Figure 2. For a minimum illuminance of 1 footcandle, the required reflectance for a 40 year old observer is approximately 50 percent. For a 70-year old patron, the required reflectance is over 70 percent. Since the average age of licensed drivers in the United States is 57 years old, lighting and visibility in parking facilities need to accommodate the elderly segment of the population. Therefore, for a 40-year old observer, the wheel stop could be painted pink (how quaint!). For the 70-year old observer, the curb or wheel stop should be painted yellow or white. I didn t want to bore you with a discussion of the theoretical formula used to make these calculations, however, it is important to know that there is a quantifiable procedure for determining the visibility of these hazards. In fact, I recently was involved as an expert witness in a trip and fall, personal injury lawsuit, which I will review with you. Case Study Photos #1 and #2 illustrate the area of the trip and fall incident. This facility is an underground parking structure for a hotel. The plaintiff parked her vehicle adjacent to an empty handicapped parking stall. She intended to cut through the stalls to the elevator in the background of the photo. As she headed toward the elevator, she was distracted by a friend just getting out of her car not too far away. Suddenly, she tripped over the wheel stop and fell. I believe she filed a claim for over $200,000 although she didn t break any bones, but apparently developed arthritis in the injured knee and was not able to continue working. I was retained by the attorney for the hotel. My investigation included measuring the horizontal illuminance on the floor with light meter at a grid spacing of approximately 5' by 5' in an area of approximately 66 feet by 32 feet. I also performed direct measurements of the luminance with a special meter designed for that purpose rather than depend on calculations based upon assumed reflectances. The average illuminance from 91 measurements was 3.45 footcandles. The illuminance measured along the bumper line at the wheel stops ranged from 0.40 footcandles to 6.08 footcandles. The higher readings occurred at one end of the line of 7 wheel stops where a

11 Charleston, South Carolina Page 10 Figure 2

12 Charleston, South Carolina Page 11 Photo #1 Photo #2

13 Charleston, South Carolina Page 12 fluorescent light was centered on the bumper line at an old cross-over aisle. The illuminance on the wheel stop over which the plaintiff fell, was approximately 0.56 footcandles. Therefore, the illuminance did not meet current IES standards. The visibility calculations are indicated in Table 5. The actual difference in luminance of the wheel stop versus the floor was determined by measurement. The luminance difference required for adequate visibility at a 50 percent probability was calculated from published research. The ratio of the actual luminance difference to the calculated threshold for visibility is called the visibility level. At a visibility level of 2.6, there is 99.9 percent probability that the wheel stop should have been seen. Only one of the measured values was slightly below a visibility level of 2.6. The average visibility level was 6.24, or approximately 2 1/2 times the required contrast for adequate visibility. It only took the jury 1/2 hour to exonerate the hotel from any liability in this case. The visibility of the wheel stop was enhanced by the fact that it was painted bright yellow. Further, there had been a black waterproofing membrane applied to the concrete floor. As noted in the previous table of reflectance values, yellow on black has one of the highest contrasts. Adequate visibility of the wheel stop was provided despite the fact that the illuminance was below IES guidelines. Therefore, it is possible to minimize your exposure to liability claims from trip and fall injuries by removing those obstacles or painting them with high contrast colors to improve the visibility. CRIME DETERRENCE How much lighting is necessary to deter criminal activity? There is no hard data that I am aware of for parking facilities that correlates light levels with criminal activity. In general, many facilities that have increased light levels have found a reduction in some types of accidents and criminal activity, but there is no conclusive evidence that improved lighting reduces crime. However, attitude surveys before and after lighting improvements indicate that patrons felt safer after the lighting improvements due to greater distance visibility and their ability to identify potential assailants and take evasive action. Studies were performed by Boyee and Rea (Reference #2) with regard to the effects of perimeter security lighting on people s ability to detect someone walking towards them along a lighted path and then recognizing them from a selection of four photographs. The results indicated that a vertical illuminance of about 0.1 fc (1 lux) is sufficient to obtain a probability

14 Charleston, South Carolina Page 13 Table 4 Table 5

15 Charleston, South Carolina Page 14 of correct detection (able to notice someone s presence but unable to distinguish facial features) of about 90%. At about 2 fc (20 lux), the probability approaches 100%. A vertical illuminance of about 1.5 fc is sufficient to obtain a correct recognition (able to identify features and expression of the person) of 90%. The vertical illuminance required for correct recognition is considerably greater than required for correct detection (approximately 15:1 at 90% probability). Rombauts et al (Reference #13) also studied facial recognition under street lighting conditions. The relationship between vertical illuminance and confident facial recognition at various distances is illustrated by the graph in Figure 3. Approximately 0.1 fc of vertical illuminance is required for confident facial recognition at a distance of 2 m (6.6 feet). Approximately 0.5 fc of vertical illuminance is required for confident facial recognition at a distance of 10 m (33 feet). Approximately 3 fc is required for confident facial recognition at a distance of 17 m (56 feet). His experiments concluded that confident facial recognition is not possible beyond 56 feet (17 m). Therefore, from these studies, it appears that a minimum vertical illuminance in the range of 0.5 fc to 1.5 fc should be provided to allow for confident facial recognition at a distance of 30 feet. Adequate reaction time to take evasive action may then be available if the patron feels uncomfortable. Further, it follows that if the lighting is adequate for confident facial recognition, then potential criminals may avoid your parking facility due to the increased likelihood of being apprehended. OTHER SAFETY & SECURITY ISSUES For CCTV surveillance, a minimum illuminance of 0.9 footcandles is required for today s stateof-the-art colored cameras. Care should be taken in the positioning of the camera that it is not aimed directly at a light fixture, or scans across a light fixture, as the camera will adjust to the brightness of the fixture, and the background detail will be lost. A study of vehicular accidents in parking lots (see reference 5) indicates that about two-thirds involve a moving vehicle striking a parked vehicle, less than one-third involve a moving vehicle striking another moving vehicle, about six percent involve a vehicle striking a fixed object, and only one percent involve a vehicle striking a pedestrian. Further, an unpublished study of a large neighborhood shopping center found that only 14% of all parking lot accidents occurred at night. An unpublished university study indicated that only 17% of all parking lot accidents occurred at night. Therefore, poor lighting may not be the cause of most accidents. Other issues such as speed, site distance, and geometric design may be more important.

16 Charleston, South Carolina Page 15 Figure #3

17 Charleston, South Carolina Page 16 SUMMARY The answers to the questions raised in the introduction are as follows: 1. What constitutes adequate visibility of slip or trip hazards? The range is from 1 to 3 footcandles minimum illuminance depending on the contrast of the object against its background and the age of the observer. 2. How much lighting is necessary to deter criminal activity? Assuming that criminal activity is deterred by the increased likelihood of facial recognition, then a minimum vertical illuminance in the range of 0.5 to 1.5 footcandles should be provided. 3. What are the lighting industry standards? The Illuminating Engineering Society of North America is generally considered the authoritative technical source for parking facilities. For covered parking facilities, the average horizontal illuminance on the pavement, and average vertical illuminance at 6 feet above the pavement, must meet or exceed an average of 5 footcandles. Also, the average to minimum uniformity ratio must not exceed 4:1. 4. Why do so many parking structures have substandard lighting? 1. Incorrect selection of light loss factors in the lighting design. 2. Inadequate maintenance of the lighting system. 5. What can be done to minimize the risk of personal injury liability in a parking facility? 1. Meet IES lighting design guidelines. 2. Eliminate trip hazards or paint hazards with a high contrast color. 3. Provide minimum illuminance of 1 to 3 fc for areas with potential hazards. 4. Provide minimum vertical illuminance of 0.5 to 1.5 fc at 6 feet above the pavement. 5. Measure the light levels in your facility periodically to determine compliance to IES standards as well as determine when lamps should be replaced and fixtures cleaned. 6. Document your lighting measurements and maintenance actions. REFERENCES

18 Charleston, South Carolina Page Adrian, Werner; The Physiological Basis of the Visibility Concept, 2nd Annual Symposium on Visibility and Illuminance in Roadway Lighting, October 26-27, 1993, Orlando, Florida, Sponsored by the Lighting Research Institute, New York, NY. 2. Boyce, P.R. and Gutkowski, J.M. (1990); Street Lighting and Street Crime, Lighting Research Center. 3. Boyce, P.R. and Gukoswki, J.M. (1990); The If, Why and What of Street Lighting and Street Crime, CIBSE National Lighting Conference, Cambridge, U.K. 4. Boyce, P.R. and Rea, M.S. (1990); Security lighting: Effects of Illuminance and Light Source on the Capabilities of Guards and Intruders, Lighting Research and Technology, 22, p Box, Paul C.; Parking Lot Accident Characteristics:, ITE Journal, December 1981, Institute of Transportation Engineers, Washington, D.C. 6. Box, Paul, C.; Avoiding Tort Claims in Parking Lots, Public Works Magazine, January, Cunnen, J.M.L.; Crime and Lighting, Lighting Design and Application, April English, William; Slips, Trips, and Falls, Safety Engineering Guidelines for the Prevention; Hanrow Press, Del Mar, California, Monahan, Donald R.; Safety Considerations in Parking Facilities, The Parking Professional, September, 1995, International Parking Institute, Fredericksburg, VA. 10. Nam, Sheela H. And Murdoch, Joseph B.; Lighting for Bus Stops, Proceedings of the IESNA Annual Conference, New York, New York, July 30-August 2, Painter, K. (1988); Lighting and Crime Prevention: The Edmonton Project, Middlesex Polytechnic. 12. Painter, K. (1991); An Evaluation of Public Lighting as a Crime Prevention Strategy: The West Park Estate Surveys, The Lighting Journal, December 1991, p REFERENCES (cont.)

19 Charleston, South Carolina Page Rombauts P., Vandewyngaerde H., and Maggeto G.; Minimum Semi-cylindrical Illuminance and Modeling in Residential Area Lighting, Lighting Research and Technology, 21, RP-20, Lighting For Parking Facilities, 1985, Illuminating Engineering Society of North America, New York, NY. 15. Lighting Handbook, Reference and Application, Eighth Edition, Illuminating Engineering Society of North America, New York, NY.