Street lighting has traditionally been installed as a matter of security, in order to prevent accidents and crime. In ancient Rome, a class of slaves called lanternarius kept oil lamps glowing around private residences. Their blazing lanterns were private protection against misadventure. Public networks of lighting developed as technology and labor allowed. In 1594, the police in Paris installed a network of lanterns in the hope it would deter lawbreakers. These networks have flourished with modern advances, including the development of the electrical grid, and now LED lighting with intelligent controls. As cars became dominant, lighting became important in preventing vehicle accidents and fatalities. In our expanding urban environments, outdoor lighting is now ubiquitous.
Yet street lighting is changing as technology, culture, and research around the topic develop. Crime prevention through environmental design (CPTED) – a foundation of traditional municipal planning – is changing. Public lighting is benefiting from this evolving perspective. Recent research suggests that community engagement, rather than built environment alone, is important in creating secure spaces. Excellent lighting design should not just be a deterrent to crime, but also attractive to the community. Supporting walkability is essential to this task: pedestrians engage at street level. Municipalities see additional benefits when they encourage active transportation like walking and bicycling. Traffic congestion, pollution, carbon footprint, and public health all improve with active solutions.
Yet the flood of light that now bathes our outdoor environment at night can interrupt the circadian rhythms of the natural world. Modern approaches to lighting must both encourage active engagement and minimize the effects of light pollution.
Illumination has been shown to make pedestrians feel safer when walking at night. In placemaking (a design philosophy that aims to support people’s health, happiness and well-being through creative, vital public spaces), this perception of safety through lighting is essential. (Check out the lighting guidelines from the Project for Public Spaces.) Research is ongoing. For example, in the UK a large study engaged with community to measure the influence of light on the social realm. People like to gather in comfortable, beautiful places that provide experiences.
In some noteworthy designs, like the light-and-fog installation at Philadelphia’s Dilworth Park (by artist Jane Echelman and Arup), lighting is in the foreground of placemaking and interactivity. Yet in most areas, quality lighting design is often unobserved, the backdrop to activity. It is most notable when absent. Lack of good lighting on wayfinding signs, pedestrian crosswalks and near hazards, makes an area less walkable. Grassroots pedestrian organizations like Los Angeles Walks often advocate for this type of lighting.
The absence of needed lighting is a hazard, but bad lighting can also be a serious problem. More light is not the same as better light. The Vision Zero Network, an organization with the mission of eliminating all traffic fatalities, reports that 3 out of 4 pedestrian deaths happen at night. In a project with Phillips Lighting, they show that unsuitable light, rather than just lack of light, is an important contributing factor to traffic fatalities.
Human perception of light is reliant on uniformity, contrast and color rendition. Where there is high contrast between illuminance levels, the human eye has trouble adjusting. A lighting grid that keeps pedestrians safe creates consistent illuminance while minimizing glare.
Glare is a hazard of non-uniformity that threatens walkability. Glare is caused by light that is many times brighter compared to surrounding light levels, through brightness and concentration. Pedestrians and drivers can become overwhelmed by glare and unable to see clearly in their visual field. While high vertical illumination is important, the intensity of glare caused by streetlighting is largely a function of light emitted at 80 and 90 degrees on the vertical angle – close to horizontal; shining into people’s eyes instead of lighting the field of view.
Color rendition is also a factor for walkability and pedestrian safety. Compared to HPS, LED lights commonly render colors more accurately. This enhancement increases visual detection and reaction times, adding to nighttime pedestrian safety and walkability.
But because of higher "blue-light" content, LED streetlighting presents a challenge to planners. Overlighting and poorly designed fixtures can cause light trespass and skyglow, potentially interfering with circadian rhythms in humans and animals. Research is ongoing regarding spectra and biological effects.
The BUG rating, a classification system introduced by the Illuminating Engineering Society in 2009, classifies the backlight, uplight, and glare of various fixtures to quantify the different light patterns of luminaires. Careful attention to high-angle brightness, controlling the uplight, is important for maintaining dark skies.
The use of low-height luminaries in pedestrian spaces, as with lighting bollards, can be used to limit glare, improving safety and comfort for both pedestrians and drivers. Low height and strict cutoff (check the BUG rating) mean less opportunity for light trespass and ecological impacts.
The role, function and responsibilities of outdoor lighting are changing. Instead of a more-is-better approach to deter crime, creative lighting design and careful fixture choices can have a foundational role in creating and sustaining community. Quality lighting design for public spaces must minimize glare and maximize visibility (with awareness of light pollution and trespass) while enhancing aesthetic beauty and public enjoyment of the area. Lighting design is a powerful tool in creative placemaking: enhancing the "experience." Lighting that enhances beauty and engages pedestrians at street level addresses traditional roles of crime prevention and safety.