Much of this lighting is concentrated in cities, bringing a range of benefits and costs to urban populations. Research by Jon Sadler and James Hale (University of Birmingham) is mapping artificial lighting to explore how these costs and benefits are distributed over cityscapes at a fine spatial resolution. These maps provide a baseline dataset that can be used to quantify and compare the lighting within and between cities, as a tool for monitoring change over time and for improving the performance of urban lighting.
Understanding the spatial distribution and quality of today’s urban lighting is important for delivering low carbon cities of the future. Lighting has considerable energetic costs which can be minimised through more efficient technologies such as LED’s and through the dimming or even the removal of unnecessary lamps. Such interventions are already underway in many areas. However, without comprehensive mapping and research it is not always clear where these are best targeted in order to maximise human wellbeing and minimise impacts on wildlife.
Lighting may also play an important role in facilitating the transition to low carbon modes of transport and more efficient development patterns. It can affect perceptions of safety and local character, and could therefore influence whether attempts to change mobility patterns (e.g. cycling) and land-uses (e.g. mixed use developments) are successful. Images of cities and neighbourhoods at night may also be useful for engaging the public in a debate about urban lighting and for generating support for broader sustainability initiatives and behaviours.
This research within the School of Geography Earth and Environmental Sciences at the University of Birmingham is funded by the Engineering and Physical Sciences Research Council (EPSRC). So far, aerial night photography has been collected for 5 UK cities including London and Birmingham. Please follow these links to view a video and research paper that explores some of the uses for this aerial night photography.
Mapping the lighting of cities
A key goal was to generate maps of lighting for UK cities, yet several projects have already recorded variation in artificial lighting over large areas. Global maps of night-time lighting have been developed using satellite mounted sensors such as the Defense Meteorological Satellite Program (DMSP) Operational Linescan Satellite (OLS) and more recently the Visible Infrared Imaging Radiometer Suite (VIIRS). These images can be striking, as illustrated in this video. Global lighting datasets have provided the basis for a growing body of research, yet the resolution is too coarse for many applications. In particular, it is not possible to identify how the quality or brightness of lighting varies within urban areas. Key questions such as which land-uses tend to be brightly lit or are responsible for most urban lamps, cannot not be answered using this data.
Photographs of cities at night have also been captured by astronauts from the International Space Station (ISS). The variation of lighting within cities is clearly visible, both in spectral quality (colour) and brightness. These are starting to be used for research applications; but the images are not calibrated at present and vary in spatial resolution, making comparison of images difficult. In addition, even with a 50m pixel resolution, it is not clear how many lamps and land-uses are contributing to individual pixel values.
Given the potential demonstrated by ISS images, the Environment Agency Geomatics Group were contracted to collect the finest resolution colour aerial night photographs yet taken for entire cities. Capture for Birmingham (UK) was funded by the Birmingham Environmental Partnership, with collection and analysis for another four UK cities funded by the Engineering and Physical Sciences Research Council. Photographs of Birmingham were taken by plane at a height of ~900m using a colour Nikon D2X digital camera, mosaiced into a single image and resampled from 10cm to a 1m pixel resolution. This was then converted into maps of lamp locations and surface illuminance, using ground based measurements and image analysis.
Analyzing the lighting of cities
The aim of this first analysis was to identify relationships between lighting metrics and land-use for the City of Birmingham, UK. Lighting maps were compared to land use data using a Geographical Information System (GIS). Roads and car parks within housing and manufacturing areas were found to be responsible for the majority of bright lighting in the city. The importance of manufacturing areas was surprising given that they represent a small percentage of Birmingham’s total land area. This implies that efforts to reduce unnecessary lighting should broaden their focus from residential street lighting to include security lighting within manufacturing areas. In addition, bright lighting increased with greater built density and was higher for land uses such as offices, retail, distribution and servicing. The suggestion is that a shift to denser cities with service based economies might be expected to result in increased levels of urban lighting. Similar work has been undertaken in Berlin, Germany; although further research is needed to see whether the patterns of lighting found in Birmingham and Berlin might be expected in other cities.
Further information on Artificial Lighting
Whilst this page is not intended to provide a comprehensive overview of lighting research and practice, the links below should help those seeking further information on key areas.
A range of guidance has been produced by professional bodies such as the Institute of Lighting Professionals (UK) and the Lighting Urban Community International (LUCI), as well as the lighting industry (e.g. Phillips or Interior Deluxe). Such guidance emphasises the need for “the right lighting, in the right place at the right time” and is updated as new technologies or practices emerge. This guidance also draws attention to a range of benefits and costs associated with artificial lighting. Poorly shielded or unnecessarily bright lighting contributes to sky-glow and has been problematic for astronomers for many years. As a result, a considerable body of information has been also collected by the International Dark-Sky Association.
Clearly there is a need for new research to inform best practice guidance as urban lighting changes. An excellent introduction to lighting costs, benefits and key research themes can be found in “Artificial Lighting in the Environment”, published by the RCEP in 2009. Labeling lighting as “good” or “bad” is generally recognised as insufficient, due to the variety of ways that lighting can affect living organisms, the different locations where lighting is used and different social expectations for its performance. A single lamp may simultaneously deliver a range of benefits as well as a range of costs. Some of these subtleties are illustrated in specific areas of lighting research such as human visual perception, health and ecology. For example, the conspicuity of lit objects is not just related to their luminance, but also to the contrast and complexity of their background lighting; exposure to light at night can effect human hormonal cycles and many insects respond to UV from street lighting that is invisible to human eyes.
For more information on the impacts of artificial light at night, we suggest visiting the LoNNe (Loss of the Night) COST network or viewing the extensive collection of lighting papers compiled by Dr Christopher Kyba as part of the “loss of the night” research project in Berlin.