Enlarge 2008 photo by John Locher, AP Lights from Las Vegas, 85 miles away, illuminate the night sky at Dantes View in Death Valley National Park, Calif., as Dan Duriscoe takes pictures. The push to turn down the lights in American cities is gaining broad support from several unlikely allies — from conservationists and builders to city planners and the military. Dark-sky legislation — laws requiring such measures as shielding outdoor lighting to reduce light pollution — has been embraced by about 300 counties, cities and towns. More than 50 state bills have been introduced in the past two years, and seven were enacted. Eighteen states —Arizona, Arkansas, California, Colorado, Connecticut, Hawaii, Maine, Minnesota, Missouri, New Hampshire, New Mexico, New York, Oklahoma, Rhode Island, Texas, Vermont, Virginia and Wyoming — have adopted dark-sky legislation in recent years, according to Bob Parks, executive director of the Tucson-based International Dark-Sky Association. EARTH HOUR: Landmarks, cities worldwide cut power The laws have won support in states such as Texas, home to several military bases, because lights at night can interfere with military drills. Trying to simulate flying over remote parts of Afghanistan is difficult when skies are aglow from city-light glare. "It's a broad environmental issue, and it's also a safety issue," Parks says. "It's a pure waste of energy, dollars, and it contributes to greenhouse emissions. ... For every watt of electricity used needlessly, somewhere a coal power plant is generating that electricity." The association, which has 5,000 members worldwide, was founded in 1988 by an astronomer in Tucson who noticed an impact of city lights on stargazing. Local ordinances were enacted to direct lights toward the ground instead of the sky and to not light areas that don't need illumination, Parks says. Since then, evidence has mounted that nighttime lights disturb animals and ecosystems. This month, findings presented at the American Geophysical Union in San Francisco showed that sky glow over cities interfered with chemical reactions that naturally clean the air at night. Fairfax County, Va., a suburb of Washington, adopted standards in 2003 that prohibit outdoor lights from shining upward. "It still provides quality lighting and lighting that's not intrusive," says Jack Reale, county planner. Before the ordinance, the glare of outdoor lights often spreads outside property lines and "in many cases was shining in a neighbor's window," he says. "The intent was to establish outdoor lighting standards that reduce the impact of glare, light trespass and overlighting and to promote safety and energy conservation. ... It's designed to put light where it's needed." Fairfax County is working to strengthen its standards. Separately, the Virginia Department of Transportation has replaced many streetlights with fixtures that shield the light from shining upward. Smaller cities have been more aggressive in changing outdoor lighting laws. Southampton, N.Y., recently passed an ordinance after more than a two-year tug of war that pitted environmentalists against citizens concerned about safety. The law sets wattage limits and the hours that outdoor lights can be left on. "Cities and local governments can adopt policies ... but it's more forceful if the state legislature comes in," says Melissa Savage, program director in Washington for the National Conference of State Legislatures. Some developers oppose the restrictions, but most support guidelines that don't change when they build outside city limits, Parks says. His group is working with the Illuminating Engineering Society, a professional group that sets design guidelines, to develop standard lighting ordinances that municipalities can adopt for new construction. Builder Ted Clifton, head of Clifton View Homes in Coupeville, on Washington state's Whidbey Island, is a fan. "It's just going to save you money," he says. "You can burn 4 watts instead of 100, and it's all lighting the surface you're walking on." Guidelines: You share in the USA TODAY community, so please keep your comments smart and civil. Don't attack other readers personally, and keep your language decent. Use the "Report Abuse" button to make a difference. You share in the USA TODAY community, so please keep your comments smart and civil. Don't attack other readers personally, and keep your language decent. Use the "Report Abuse" button to make a difference. Read more