While electric lighting is helpful during nondaylight hours in terms of safety, security, and improved economic development, too much nighttime illumination sometimes can cause problems, interfering with stargazing, animal health, or human sleep cycles. Scientists at the Lighting Research Center (LRC) at Rensselaer Polytechnic Institute in Troy, N.Y., have been studying this and have developed, according to a recent LRC press release, the first-ever comprehensive method for predicting and measuring various aspects of light pollution.

LRC's method, called Outdoor Site-Lighting Performance (OSP), enables users to quantify the performance of both existing and planned lighting designs and applications, which then allows them to minimize excessive light from leaving property boundaries. OSP addresses three aspects of lighting pollution: sky glow, which is the total amount of light leaving a property; light trespass, which is described as the amount of light that crosses from one property boundary to another; and discomfort glare, which is a prediction of the level at which light coming from a luminaire is uncomfortable for viewers. These three factors are independent of one another, but each is measured by OSP, which lets users control and maximize the positive benefits of nighttime lighting.

Developed to assess outdoor lighting performance, the OSP method can be used with any commercial lighting software. Using the software, designers can create a calculation “box” that follows the property line between private and public spaces. To figure out values of glow, trespass, and glare, LRC scientists worked with application engineers and studied 125 lighting designs for four common nighttime lighting applications: car parking lots, roadways, sports fields, and plazas. Lighting engineers can use OSP currently, as it can help them compare various lighting design alternatives for the same site.

Scientists at LRC began this project in 2005, when lighting manufacturers approached the center in search of an objective and unbiased assessment of light pollution. The LRC's research was funded by Acuity Brands Lighting, Lumec, Philips Lighting, and R-Tech Schreder. Details of the OSP method have been published in the journal Lighting Research Technology, Vol. 40, No. 3, 2008. More information can be found via the LRC's website at www.lrc.rpi.edu.