Lights are rather like vital organs: most people never think about them unless they fail. And, as with vital organs, failure can mean disaster. Street lights, in particular, are an integral part of every city, serving both as navigation devices and safety assurance. Keeping them from failing is a job city officials take very seriously.

Regular maintenance --- replacing broken bulbs or correcting faulty wiring --- comprises most of the lighting needs in cities and counties. In recent years, however, aesthetic considerations and ongoing safety concerns, as well as problems of light pollution, have prompted many municipal light refurbishment projects.

Technicalities One of the major lighting questions concerns the choice of the actual lamp. Options include low-pressure sodium (yellow), high-pressure sodium (orange-yellow lamps), metal halide (white-blue lamps), mercury vapor, fluorescent, neon and incandescent lights. Typically, engineers choose between metal halide and sodium lights for outdoor fixtures.

Until recent years, high-pressure sodium lamps usually were selected for use on streets or major highways, where aesthetics are not as important as workability. They are less expensive than metal halide lamps, which originally were produced in the 1960s for stadium lighting and other high-wattage applications such as parking lots. In recent years, however, metal halide lamps have become more common because they offer higher efficacies (lumens per watt), longer life spans and, to some, a more appealing glow, according to Sri Rahm, technology and training consultant for Venture Lighting, Solon, Ohio.

Many cities have converted existing sodium fixtures to halide for aesthetic reasons, but the conversion process can be costly and lengthy. The swap requires exchanging the electrical system --- ballast, capacitor and ignitor --- with a metal halide system. If engineers intend to use the original post or fixture, they may not be able to increase the wattage significantly because the posts commonly have limitations. If increasing the wattage is the reason for the re-fit, cities or counties may do better to scrap original fixtures and start fresh, according to Rahm.

Form and function "There is a greater appreciation and interest in lighting, and an understanding that it goes beyond the function," says Tom Kaczkowski, who heads lighting design for Helmuth, Obata + Kassabaum, a St. Louis engineering firm known for its ballpark business. "[Cities] have to look beyond the cheap workability."

As Denver exemplifies, efficiency and aesthetics are not mutually exclusive. Denver has been able to combine efficiency with decoration. In 1997, the city's 16th Street Mall, a pedestrian retail area, boasted 194 15-year-old streetlights designed by architect I.M. Pei. The fixtures were unique and attractive, but they really did not project enough light for the pedestrian traffic, says Yvette Freeman, manager of the Downtown Denver Business Improvement District. The city wanted to keep the original light fixtures but also make the lights brighter and more efficient to decrease maintenance costs.

With a budget of $500,000, engineers replaced the original "twinkle" lamps in each streetlight with a fiber-optic system that reflects a single beam of light throughout the fixture. The new lamp reflector combination provides 20,000 hours of service and triples the light output level. The fiber-optic point sources cannot burn out, saving the city maintenance costs. The lamps, which have 20 times the life span of the old lamps, are the only pieces requiring replacement. In addition, the original polycarbonate globes, which had become discolored over time, were replaced with clear acrylic globes.

Denver is now in the middle of a $3.2 million streetscape improvement project on 17th Street. The 10-block stretch under renovation will receive new light fixtures with higher levels of light, new benches and trash receptacles, and new traffic signal lights. While Denver has preserved its unique, early-'80s look, other cities have taken design a step further --- backward, that is --- to incorporate 19th century styles in materials such as wrought iron. In Winter Park, Fla., for example, city engineers recently installed new "old" posts throughout the Park Avenue area.

Winter Park's light poles, from Niles, Ill.-based Sternberg Vintage Lighting, include arms for planters or banners. The planter arms feature drip irrigation systems that automatically water plants, saving the city the required time and expense of doing so. Posts with banners display information about city events.

Frequently, an upcoming city event provides the impetus for a refurbishment. Cleveland, for example, capitalized on a major city event in 1996 --- its 200th birthday --- to initiate lighting improvement projects. The city focused on the Lake Erie area, which is anchored by the RTA Waterfront line that provides transportation from downtown Cleveland to the lakefront.

According to Dale Turkovich, consulting engineer for Cleveland Public Power and the city, residents expressed the desire for an historical look in the area. Turkovich chose decorative poles, from Commerce City, Colo.-based Whatley, that replicate the area's original cast iron poles, with luminaires that resemble lanterns. Rail stations received four-lantern posts, and surrounding streets received single luminaires.

Because the city has so many lights (more than 500 new fixtures were purchased), Turkovich selected fixtures that allow multiple wattages. The light level can easily be changed depending on the part of town in which a fixture is placed. For example, he says, main thoroughfares carry 400 watts, while residential areas carry 150 to 175 watts. Using only one fixture style or several similar styles ensures design consistency across the city.

While some refurbishments occur citywide, others may be limited to a particular area known for heavy traffic. In Frankfort, Ill., recent street improvements have focused attention on the historic district. Two roadways, Lincoln Highway and U.S. Route 45, received new lights in an attempt to turn more traffic toward the historic district. "The village has set the preservation of its past as a priority, and downtown is our gem," says Paula Wallrich, director of Frankfort's community development. "The streetscape enhancement has provided an original identity and a wayfinding device to the historic district."

Baxter & Woodman engineers of Crystal Lake, Ill., installed custom-designed light fixtures in Frankfort. Because the district is surrounded by residential areas, Frankfort chose fixtures with "caps" to ensure that light aims downward, onto sidewalks and streets for safety and to prevent light spillage.

Safety first When adding decorative features to light posts, it may be easy to forget the safety components of lights. Of course, the main purpose of lighting is to ensure safety. But, when city councils plan and budget lighting, they may focus only on attractive lighting for streets and sidewalks, neglecting basic lighting for alleys or other outdoor spaces. "People are very concerned about safety, and cities are concerned about liability and sufficient lighting," says Angela McDonald, principal with Horton Lees Lighting Design in San Francisco. "Dark buildings, dark doorways and dark alleys can make a pedestrian experience uncomfortable."

Recent lighting projects in Clayton, Mo., targeted safety. "Lighting really provides the opportunity to make a nighttime streetscape a very user-friendly environment for pedestrians," says Bryan Pearl, director of public works. "It adds life and more security." Clayton recently underwent $3 million worth of improvements to add new lights and other features to its central business district.

Ensuring security also requires providing enough light between fixtures to provide continuous illumination. Most cities have specific standards in place for that purpose. In Wagoner, Okla., for example, street lights are placed 40 feet apart. Actual lamps sit 10 feet off the ground.

"One of the tricks to creating a successful project is using a lot of different layers of light. Cities don't need a high level of light everywhere," McDonald explains. Light layering is a technique that can allow cities to save money and ensure safety through efficient lighting techniques. For example, streets and sidewalks require high levels of light for navigation, but buildings that are unoccupied at night do not require brightly lit parking lots, nor do shrubs or garden beds.

The master plan To create an efficient lighting system, cities need a cohesive master plan, McDonald says. "Having a master plan allows for well-thought-out reasoning and a set of standards for people who maintain the lights," she notes.

Most cities outsource their lighting design work to private companies, but they thenmust perform their own maintenance, which can cause some confusion. "It's difficult for cities to make the realities of long-term maintenance match the original design concept," McDonald explains. Additionally, because maintenance engineers usually are not involved in the original design process and discussion, they may not be aware of some of the lighting features.

If a city's budget allows, McDonald says, companies may write up a summary report with diagrams, wattage standards and other details for city engineers to check after the fact. But, she adds, it is better for a maintenance engineer to be involved from the project's initiation to avoid mishaps.

Light pollution, also known as over-lighting or light spillage, is one such mishap. It occurs when buildings or streets are lit too brightly, have too many lights or have misdirected light. "You want to drive lights to the ground, not up," Kaczkowski says.

Excess light is wasteful, but the glare of bright lights also can be dangerous for drivers. After their eyes adjust to a high light level in one area, a sudden switch to lower light levels makes it difficult to see. "It's a safety problem for your eyes to adjust to different levels," says Tyler Gibbs, director of urban design for Denver. "It's something we're becoming more aware of."

In fact, Denver officials recently held a seminar to discuss appropriate light levels and are incorporating new lighting criteria into city building guidelines. The criteria will include specifics for downcast lighting and shielded lighting.

Out West, excess lighting has created a unique problem by disrupting astronomical observations, according to astronomer Alan Dressler of the Carnegie Observatories in Pasadena, Calif. In fact, he says no new observatories are being built in the United States because there are no longer enough dark areas. "Much of what astronomers do involves looking at faint things very far away," Dressler says. "When local light mixes with the light in the sky, it obliterates the signal from the sky."

To create awareness of light pollution hazards, the International Dark Skies Association, a Tucson, Ariz.-based organization of astronomers and others dedicated to reducing light pollution, offers a list of non-polluting fixtures on its web site (www.dark sky.org). They include downcast box lights, flat lenses, lights with top caps or covers, and floodlights with top and side shielding. Caps are available on many decorative or vintage style lights as well. The association also encourages the passage of light ordinances in cities and counties.

In fact, a 1994 ordinance in Tucson provides specific standards for outdoor lighting "so that its use does not unreasonably interfere with astronomical observations. It is the intent of this Code ... to conserve energy without decreasing safety, utility, security and productivity while enhancing nighttime enjoyment of property within the jurisdiction." The ordinance lists nighttime regulations and shielding requirements for specific types of lights, such as high-pressure sodium and metal halide lamps. It also prohibits uplighting, such as search lights (for commercial use) or floodlights.

"There's a renewed interest in making monuments and buildings more prominent," Kaczkowski says. "Floodlighting, in particular, can be perceived as a waste of energy." McDonald says that floodlighting can add to a corporate or civic identity by highlighting a skyline or logo, but light at high angles is useless. Floodlights must be tailored to the size of the building or structure to minimize spilled light.

If spilled light is inefficient, over-lighting can be downright annoying. Gas stations and car dealerships are among the most serious commercial users of excessive lighting, but city facilities such as airports, hospitals, recreational centers and athletic fields are guilty as well. All outdoor lighting may be subject to regulations by city ordinances.

A 1997 ordinance in Branford, Conn., for example, calls for all parking areas to use full cut-off type fixtures. It also states that "all non-essential lighting will be required to be turned off after business hours, leaving only the necessary lighting for site security." "People feel very strongly that better-lit places have less crime," Dressler notes. While light does play a role in security, however, more is not necessarily better. As more cities refurbish their lighting schemes, officials also will need to pay attention to concerns and ordinances regarding light pollution.

Lights are a constant expense in cities, but they are an integral part of streetscapes and roadways. Lights also can play a significant role as a reminder of a city's history while still serving their purpose as a safety device.

County office buildings typically keep lights on 24 hours a day for security. The costs for that safeguard usually are extravagant, but they can be avoided through different means of conservation.

In Alachua County, Fla., light load shedding, light management and "daylight harvesting" have cut costs at a downtown building. Through gradual dimming, a ballast retrofit and computerized light management, the county has saved more than $20,000 a year in energy costs.

The 20-year-old, three-story, 34,000-square-foot brick building, originally a bank, houses 70 county employees. Business hours are 8 a.m. to 5 p.m. Monday through Friday, with up to six hours of occupancy during the weekend. However, prior to 1998, at least 80 percent of the lighting had been running 24 hours a day.

"We didn't have a management system on the lighting," says Charles Balanis, energy management specialist for 40 county buildings. "I don't think building managers even thought about turning the lights off." Computerized load management historically has focused on interruptible loads such as air conditioners and hot water heaters. But, when applied to lighting, the tool allows facility managers to monitor energy demand, gradually dim the lights by up to 30 percent, increase lighting when needed, and control and track the entire process by computer. The changes typically remain unnoticeable to the occupants.

Chem Light Plus, Gainesville, Fla., and Electronic Lighting, Newark, Calif., partnered last year to design and install Alachua County's new load management system. Since the project's completion, the building's electrical energy consumption has dropped 76 percent, producing a 34 percent savings on the facility's total electric bill. The system, which cost $49,000, is expected to pay for itself in two and a half years.

Prior to computerizing its load management system, the county implemented several new mechanisms --- occupancy sensing, manual turning and daylight harvesting --- in the building. Additionally, the county completed a building-wide retrofit, replacing 406 drop-ceiling lighting fixtures containing standard magnetic ballasts with controllable electronic ballasts. The new fixtures reduced the wattage from the 158-to-174 range to 58 watts per fixture.

Occupancy sensors for on/off control were installed in wall switches in every office and in the ceiling above open offices and cubicles. Some of the offices were fitted with manual dimmers, and the perimeter offices with windows received photosensors for daylight harvesting (the dimming of lights as daylight increases).

All of the components are connected to the light management system that gradually dims lights when the local demand exceeds 65 kilowatts and restores them when load drops below 60 kilowatts. Cost savings rapidly accumulate, since, in a typical building, lighting represents 30 to 50 percent of the total electric load.

"It's working. We're seeing tremendous drops in kilowatt/hour (kwh) consumption," Balanis says. "People are completely unaware the lights are gradually dimming, and I get to watch the energy savings."

Savings on the project were immediately evident. Consumption dropped 21,600 kwh the first month over the same period the previous year. And an even more dramatic reduction of 32,000 kwh was recorded the month following implementation of the lighting management system in May. Energy reduction now tota ls 270,300 kwh annually. Balanis says he plans to use lighting management systems in other county buildings in the future. "I reap the savings by regulating the load on demand, and I don't have to worry about employee complaints," he says.

For nearly 30 years, Philadelphia relied on private maintenance contractors working along with city forces to keep the city's 100,000 streetlights aglow. Last year, however, the city outsourced the job, improving efficiency and cutting costs.

Philadelphia owns its streetlighting system, but the local utility, PECO Energy, owns the electrical distribution system and all of the wooden poles that support transmission lines. The maintenance always has required coordination between the city, the utility and contractors.

When PECO Energy launched a business to compete with private maintenance companies, Philadelphia officials saw an opportunity to streamline their streetlight maintenance. They awarded a contract to the utility's new affiliate, Exelon Infrastructure Services.

"In the old world, a utility would make repairs if the problem was related to its equipment," says Joseph Doyle, Philadelphia's streetlighting engineer. "The contractor would identify the problem, write up a work order, and the utility would dispatch a crew separately to go out and fix it. In the new world, the contractor has the authority and skill level to make immediate repairs."

Under the contract, every streetlight receives a weekly, night-time inspection. Those needing lamp or photo control repair are returned to service within 24 hours. The repairs are performed at night, avoiding the common daytime mistake of "repairing" the wrong light. Two-thirds of all the repairs occur before a resident calls to report a problem. When a call comes in, it goes directly to the contractor's 24-hour customer service center, where it is processed accordingly for repair work.

In addition to speeding response time, the city has saved money through the provider's inventory capabilities. "In the past, cities have tended to be conservative and stockpile what they might need," Doyle says. "In the competitive world, a contractor is able to maintain lean inventories and flexible contracts with suppliers."

Doyle estimates that outsourcing has saved Philadelphia $2 million over its previous streetlight maintenance contract. However, he is primarily pleased with repair improvements. "Streetlights need focused attention," Doyle says. "Having an efficient, fail-safe system in place ensures that, when you look out your window at night and a light is not burning, it will be fixed --- usually within 24 hours, even if you don't make a call."

As a growing Cleveland suburb, Solon, Ohio, has, in recent years, expanded its community facilities to accommodate the needs of a diverse population and widening industrial base. Lighting has played a role in many projects, including construction of Portz Parkway, a new street located near a school, a recreation center and a new county library.

As Solon officials made plans for lighting Portz Parkway, they wanted to create an appealing, natural lighting scheme and establish a lighting standard for future city projects. Night Vision Lighting Services, a Cleveland-based firm, designed and installed the new system.

Designers selected customized decorative light fixtures mounted on fluted fiberglass posts from Hadco, Littlestown, Pa., and 150-watt Uni-Form pulse start lamps from local firm Venture Lighting. The luminaires and lamps were used for Portz Parkway and also for the parking lots at both the library and recreation center.

Because the street is located in a wooded park setting, designers chose metal halide lamps to emphasize the natural colors of the surrounding foliage. Though the initial costs were higher than those for high-pressure sodium lamps, the metal halide lamps have reduced the city's long-term energy costs.

Solon opened the new street last June. "The city has received numerous compliments on Portz Parkway that can be attributed to the lighting," says Sally Jo Reemsnyder, manager of engineering services for Solon. The same fixtures and lamps will be used to light streets and parking areas in future projects, including a new community center.