Smart urban density requires smart lighting

Denise Fong

One of the core aspects of making our cities more sustainable is increasing density while maintaining or improving livability. Locating housing near transit hubs and mixing residential, commercial and civic uses with retail and recreational uses makes our cities more walkable (or bikable). With this increased density, city streets obviously become more active with pedestrians.  But designers of urban environments spend much effort developing the streetscape to accommodate daytime activity while relatively little effort is invested in addressing how the streetscape changes after dark. Quality lighting is a key element to well-planned urban environments and proper lighting design can result in the lowest energy use, the least cost for maintenance, the most flexibility and an increased sense of safety that will keep urban residents walking and biking, even after dark.

Typically city planners take an engineering viewpoint to lighting. They focus on installing the amount of light required by codes for the least cost. This leaves out an extremely important part of creating streetscapes that are truly sustainable: walkability after dark.

Addressing these lighting issues means first re-examining our understanding of how our eyes work at night. Pilot test sites where light sources with improved color quality are used suggest that lower light levels provide adequate visibility and allow us to see colors accurately. We can also improve visibility by reducing glare and by designing the right degree of uniformity of coverage. Selecting special elements to highlight, like public art or architecturally significant buildings, helps enliven the nighttime environment and further enhances the sense of safety.

Exploring new lamp technologies also offers the possibility of incorporating advanced controls that have not been practical for exterior lighting before now. Incorporating them in an integrated way will result in the most energy efficient system.

We currently design street lighting for the peak of car and pedestrian activity, a period that lasts about one to two hours per night. Reducing light levels as the city's activity level decreases saves energy and helps maintain a view of the stars, even in dense urban environments, without reducing visibility or safety. This was demonstrated in a project we visited in Albi, France where the lighting was dimmed as nighttime activity decreased; the public did not perceive the change as it happened gradually. 

In Paris, every light on the roadways, bridges and monuments is mapped as another energy-saving strategy. These control systems can also report their failures and replacements of burned out lamps happens within 24 hours. This strategy avoids the need to over-light and saves on maintenance costs because city staff only go out to known outages.

High pressure sodium (HPS) lamps are the most common street lighting source used currently but produces poor color quality, has an unnaturally warm color temperature and cannot be dimmed. Newer lamp types such as LEDs, ceramic metal halide, fluorescent,, LIFI—a product developed by Luxim—and induction, can mitigate these negative characteristics making all of them more viable options for a sustainable street lighting system. 

Many cities are exploring the use of light emitting diodes (LEDs) as a replacement for their current systems and have implemented pilot projects. In Seattle, a recent test showed that color quality and glare were significant issues to residents and that further work on LED fixture selection would be necessary.  But if these test projects only involve one-for-one replacements, they will never address the real qualitative issues and will never result in a truly sustainable system. 

Consequently, converging systems of lighting and controls can blur the lines between design work performed by lighting designers, electrical engineers and technology consultants. A close collaboration between the disciplines will result in a comprehensive solution that not only optimizes the quality of the lighted environment, but creates a synergy with other citywide functions, such as networks that track buses in real time or those that allow first responders to control the lighting locally for an emergency situation.

There is no "one size fits all" solution for successfully lighting an urban environment because each city has unique interests, characteristics and needs. A comprehensive lighting master plan can address individual neighborhoods, examine light quality (light source selection, color quality, controls, uniformity, light levels and special features such as public art), energy efficiency and maintenance. This would be a worthwhile investment for any city. A city that feels as safe and walkable at night as it does during the day is a truly sustainable city.

Denise Fong, IALD, LEED AP, is a principal with Candela, Seattle, WA. Ms. Fong has more than 25 years of lighting design experience and has developed lighting systems for commercial, healthcare, education, hospitality, municipal and civic developments. She has been honored with many design awards for her innovative and creative lighting design work.