What Is a Lighting Impact Assessment and When Is One Required?

Artificial lighting is often essential to a development. It can support safety, accessibility, security and the successful use of outdoor spaces after dark.

However, poorly considered lighting can also affect neighboring properties, wildlife, landscape character and the wider night-time environment.

A Lighting Impact Assessment helps demonstrate that a proposed lighting scheme has been properly considered and that any potentially harmful effects have been avoided or reduced.

What is a Lighting Impact Assessment?

A Lighting Impact Assessment is a technical report that evaluates how proposed lighting could affect its surroundings. it considers more than whether a site has enough light. It examines where the light will fall, how bright it will be, when it will operate and whether it could create the following:-

* Light spill onto neighboring land or buildings

* Glare or excessive brightness

* Sky glow

* Disturbance to residents

* Effects on bats and other wildlife

* Loss of dark corridors

* Changes to landscape character or dark-sky conditions

* Safety concerns for nearby road users

The assessment should provide measurable evidence, not simply state that the proposed lighting will have a low impact.

When might one be required?

A Lighting Impact Assessment may be requested as part of a planning application or required through a planning condition, It is particularly relevant where a development includes:

* Large-scale exterior lighting

* Car parks, service yards or access roads

* Sports pitches or floodlighting

* Commercial, industrial or logistics facilities

* Residential development near existing properties

* Illuminated buildings, signs or public spaces

* Sites close to protected landscapes or dark-sky areas

* Habitats used by bats or other light-sensitive species

* Lighting close to trees, hedgerows, woodland or water

Requirements vary between local planning authorities. The scale of the development, sensitivity of the location and type of lighting proposed will all influence the level of information required.

What should the assessment include?

A well-prepared Lighting Impact Assessment will normally bring together the design information and calculations needed to understand the likely effects of the scheme.

Depending on the project, this may include:

* A description of the site and its surroundings

* Identification of nearby residents, habitats and other sensitive receptors

* The appropriate environmental lighting zone

* Existing or baseline lighting conditions

* A lighting layout showing luminaire positions

* Mounting heights, aiming directions and equipment specifications

* Horizontal and vertical luminance calculations

* Isolux or light-spill diagrams

* Assessment of glare, sky glow and light intrusion

* Proposed hours of operation

* Details of dimming, timers, sensors and curfews

* Ecological constraints and protected dark corridors

* Measures introduced to avoid or reduce adverse effects

* Confirmation of the guidance and standards used

The information required should be proportionate to the development. A small rural scheme beside a bat corridor may need a different assessment from a floodlit sports ground or urban commercial development.

Is it the same as a Lighting Strategy?

Not quite a Lighting Strategy sets out the overall design approach, what needs to be illuminated, how the scheme will function and the principles that will guide it. A Lighting Impact Assessment evaluates the likely effects of that proposal on people, wildlife and the surrounding environment. A Lighting Method Statement explains how the approved lighting and mitigation measures will be installed, controlled, checked and maintained.

These documents may overlap, and some planning authorities use the terminology differently. It is therefore important to read the exact wording of the planning requirement before preparing the report.

Why should it be considered early?

One of the most common mistakes is treating the assessment as paperwork to be completed after the lighting layout has already been designed. If sensitive receptors are identified early, the lighting can be developed around them. This may influence:

* The position and height of luminaires

* Beam angles and optical control

* The amount of light provided

* Colour temperature and spectral content

* Operating hours

* Dimming and switching arrangements

* Areas that should remain unlit

Early consideration can prevent redesign, planning delays and unsuitable product substitutions later in the project.

More than a calculation exercise

A computer-generated lighting plot is an important part of an assessment, but it is not the complete assessment. The results must be interpreted in the context of the actual site. Topography, vegetation, buildings, reflective surfaces, existing lighting and ecological features can all affect the outcome. The aim is not simply to achieve numerical limits. It is to create a scheme that provides the right light, in the right place, at the right time, without unnecessarily affecting the surrounding environment.

How Circalume can help

Circalume prepares independent Lighting Impact Assessments for planning applications and the discharge of lighting-related planning conditions.

We work with architects, developers, landscape architects and ecologists to identify potential issues early and develop lighting proposals that balance the needs of the project with residential amenity, ecology and the night-time environment.

Need help understanding what your planning authority has requested? Contact Circalume to discuss your project.