Introduction
An obtrusive light assessment is often required for UK planning applications involving external lighting. Poorly controlled lighting can lead to objections from neighbours, highway safety concerns, or environmental impacts.
Artificial lighting, if not properly designed, can cause nuisance, reduce residential amenity, and negatively affect biodiversity. Inappropriate lighting levels may also conflict with local planning policies aimed at protecting dark skies, particularly in rural or semi-rural areas. As a result, planning authorities frequently seek technical evidence demonstrating that proposed lighting has been carefully considered and designed to minimise adverse effects.
This blog explains what an obtrusive light assessment involves, how ILP GN01 guidance is applied, and how the assessment supports planning approval.
What Is an Obtrusive Light Assessment?
An obtrusive light assessment evaluates the impact of artificial lighting beyond the site boundary. It focuses on how light affects surrounding areas rather than lighting performance within the site.
The assessment considers:
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Light spill into neighbouring properties
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Glare affecting receptors
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Sky glow and wider visual impacts
It ensures lighting proposals are appropriate in planning terms, proportionate to the setting, and compliant with recognised guidance such as the Institution of Lighting Professionals (ILP) GN01 standards.
When Is an Assessment Required?
Local planning authorities may request an obtrusive light assessment where:
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External lighting is proposed
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Development is near residential properties
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Lighting could affect highways or public spaces
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The site is close to darker rural areas
The requirement depends on site context and lighting design. Larger commercial schemes, sports facilities, car parks, and industrial sites are particularly likely to require assessment, especially where lighting columns are tall or luminaires operate overnight. Even smaller developments may require supporting evidence if neighbouring occupiers could reasonably experience light intrusion or glare.
Understanding ILP GN01 Guidance
ILP GN01 provides guidance on:
- Limits for obtrusive light
- Environmental lighting zones
- Assessment criteria for planning
Obtrusive light assessments commonly reference ILP GN01 to demonstrate compliance with accepted standards.
What Does the Assessment Cover?
Site Context and Lighting Environment
The assessment reviews:
- Surrounding land uses
- Lighting sensitivity of the area
- Relevant environmental zones
This ensures the assessment reflects local conditions.
Lighting Design Review
An obtrusive light assessment considers:
- Luminaire type and orientation
- Light distribution
- Proposed operating hours
This helps identify potential impacts early.
Assessment of Impacts and Mitigation
Where impacts are identified, the assessment proposes:
- Adjustments to lighting design
- Shielding or reorientation of luminaires
- Operational controls
Mitigation should be practical and effective.
How an Assessment Supports Planning
A well-prepared assessment helps to:
- Reduce objections
- Demonstrate policy compliance
- Support a positive planning decision
It shows that lighting impacts have been responsibly addressed.
Conclusion
An obtrusive light assessment is an important planning document for developments involving external lighting. By applying ILP GN01 guidance and proposing proportionate mitigation, it helps ensure lighting schemes are acceptable.
Early assessment can help avoid planning delays and redesign later in the process. It also provides reassurance to planning officers, consultees and neighbouring occupiers that lighting impacts have been properly evaluated and responsibly controlled. A clear, evidence-based report supports smoother decision-making and reduces the risk of future complaints.
Frequently Asked Questions
Q1: Is ILP GN01 mandatory?
A1: It is guidance, but it is widely used by planning authorities when assessing lighting impacts.
Q2: Does an obtrusive light assessment include lighting design?
A2: It assesses the proposed design but does not replace a full lighting design service.
Q3: Who reviews obtrusive light assessments?
A3: Planning officers and, where relevant, highway or environmental consultees.
If your development requires an obtrusive light assessment, contact Hawkins Environmental on 01256 522332 or email enquiry@hawkinsenvironmental.co.uk.