Perceptions of safety at night in different lighting conditions

Lighting has been shown to be an effective tool in the fight against crime, but too often the tool has been a sledgehammer. The four field studies described in this paper set out to answer two questions: 'How much light is needed to provide a perception of safety at night in urban and suburban areas?' and 'How important is light spectrum to that tion?' The first two field studies examined people's perceptions of the quality of the lighting for security on streets in New York City and Albany, New York. The third measured people's perceptions of safety when walking alone in urban and suburban parking lots, by day and night. The fourth measured perceptions of safety in a parking lot lit by high-pressure sodium and metal halide lamps. Taken together, these studies indicate that an average horizontal illuminance on a parking lot surface or street sidewalk of about 30 Ix provides enough light to ensure that perceptions of safety are close to what they are in daylight. The light spectrum is a minor factor relative to illuminance.