Glare Control

The factor most destructive to lighting performance is glare. Simply stated, glare is bright direct light from an unshielded source. At night, the human eye is drawn to the most luminous element in its field of vision. Uncontrolled, glare is distracting, causes discomfort to the viewer, and adversely affects visibility. Glare entering the eyes causes them to constrict and impairs one's ability to respond to outdoor light levels.

Two forms of glare are recognized. The most obvious form, discomfort glare, causes us to avert our eyes from its source. The effects of discomfort glare are mainly psychological; i.e. a feeling of discomfiture, increasing irritation, and tiredness. The second type of glare, disability glare, results in reduced visual performance and visibility. Both types of glare are potentially dangerous and influence traffic safety. If one is consciously aware of the fixed overhead lighting, he is in all probability suffering the adverse effects of both discomfort and disability glare.

There was a time when ``the brighter the better" was a working rule of outdoor lighting, and glare was associated with performance, even though it actually reduced visibility and could be a neighborhood nuisance. If nothing else, glare is wasteful, indicating that light is being distributed at useless angles. As a result, the economy factor has been added to those of safety and comfort.

In 1969, the introduction of Gardco's sharp cutoff luminaire virtually eliminated disabling glare at normal viewing angles. Removing glare from outdoor illumination by means of sharp cutoff luminaires was an important step in the improvement of lighting performance.