Published In January 2000
Finding a safe place to park your car while you work, shop, or run simple errands is a frustrating problem most of us have encountered, one some of us battle daily. Parking spaces in busy commercial areas can be scarce and oftentimes tend to be costly. In fact, customers can actually be deterred from shopping in certain areas because of the poor parking situation. Safety in particular is the overriding issue for many individuals who fear parking in isolated outdoor lots or in large, multitiered underground garages where they fear being hit by another vehicle while walking or worse yet, attacked and robbed. Vehicle security is another huge concern, since isolated, shadowy spaces can provide the proper environment for car theft or vandalism, particularly at night. Good parking design means good business Business owners and operators are realizing that it is good for business to provide parking garages or parking lots that address these concerns. Good parking lot or parking garage design means providing a well-lit, clean atmosphere that is safe for pedestrians and drivers, and that helps prevent crime. Proper lighting in parking areas creates the visibility that necessary for our personal safety. In particular, pedestrian and driver visibility and safety depend upon appropriate and efficient after-dark lighting. Effective lighting at night gives a feeling of safety because it properly illuminates potentially dangerous areas and allows us to see possible hazards and avoid them. The important elements for contractors to consider when selecting the right light source for parking areas are light quality and uniformity. The objective should be brightness without glare, good color output, and sufficient light to prevent shadowy areas. Research tells lighting story As a contractor, you may be wondering which of the many light source options available on the market today most successfully meets these criteria. Recent research shows that the color output of a light source has a significant effect on how well we see at night. Moreover, the eye's response to color depends upon the amount of light available. Studies show lumen output of a lamp is effectively modified because the color sensitivity of the eye changes at different light levels. Under low light levels, the eye's sensitivity to yellow and red light is greatly reduced, while the response to blue light is greatly increased. For example, the red output of an incandescent lamp is very high, but the response of the eye to red under daylight conditions is low. Consequently, the red output produces only moderate lumens. On the other hand, the yellow output of the incandescent lamp is moderate, but the eye's sensitivity to yellow light under high light conditions is very high. Therefore, the yellow output of the lamp produces much of its lumens. This is why an incandescent lamp is seen as a slightly yellowish light, although its main output is red. The light source choices Sodium produces light that is primarily yellow. Eye sensitivity to yellow under high light levels is very high. Therefore, high-pressure sodium (HPS) lamps have high lumen ratings as perceived by the eye. Under low light conditions, however, the effective lumens are greatly reduced because sodium produces very little blue and green light. Almost all energy output with this light source is in the yellow region, producing very high lumen output under high light levels, but poor output under low light levels. In addition, HPS lamps emit yellow light at 2200 Kelvin (K) and have a very poor color rendering index (CRI) of 22. CRI compares a light source's ability to render colors to a standard with a CRI of 100. HPS is available in color-corrected versions. Unfortunately, they shorten the lamp's life and only slightly improve the color temperature. Although the CRI is improved in color-corrected HPS, the color temperature remains yellow. In contrast, a typical metal halide lamp has strong light output in the blue, green, and yellow regions. The result is a high lumen output for this light source at all light levels. The blue light output of metal halide is in the high sensitivity region of the eye for low light levels. This means that a metal halide lamp's effective lumens actually increase as the light level reduces and the eye shifts to a high blue/green sensitivity. Metal halide lamps produce white light, are compact, have a long life, and offer superior energy efficiency. Standard metal halide lamps produce bright white light without glare with color temperatures ranging from 3200K to 4000K and CRIs from 65 to 75. Metal halide's high efficiency can have a tremendous impact on energy usage without sacrificing light output, so fewer metal halide lamps can produce the same light output. Moreover, UV-blocking metal halide lamps are available for parking garages in a range of wattages, from 50 to 400, in open fixture designs. These lamps feature a specially treated quartz shroud that reduces ultraviolet light output by up to 80 percent. UV light emissions cause fading and damage to plastics used in fixture lenses, thereby reducing light output. These UV-blocking lamps virtually eliminate the yellowing of polycarbonate fixture lenses and thereby prolong the maximum light output of the metal halide lamps. Metal halide lighting produces light that is closest to natural sunlight of all available light sources. People like this lighting better than the HPS yellow light. Its exceptional color output and efficiency make it the perfect choice for parking garage and parking lot applications, enhancing the sense of safety for pedestrians and drivers, and reducing costs for business owners.