Luminance limits for illuminated signs and displays

An illuminated shopfront sign is controlled under the Town and Country Planning (Control of Advertisements) (England) Regulations 2007, and the only two matters a council may take into account are amenity and public safety. Brightness sits inside both. Too bright for the street is an amenity objection, too bright for a driver approaching a junction is a safety objection, and the luminance figure written into a condition is how the authority settles the argument in advance.

Luminance is measured in candelas per square metre, and the limits applied to an illuminated sign depend on the environmental zone the site falls in and, for most guidance, on the area of the display. A sign that would be accepted on a retail park beside a dual carriageway will be refused on a village high street at the same output.

Advertisement consent is a separate regime

Advertisement consent is not planning permission. It runs under its own regulations, it is decided against its own two tests, and it is normally granted for five years rather than indefinitely. A business can hold planning permission for a change of use and still be refused consent for the sign that goes on the front of it.

Two overlaps catch people out. On a listed building, illuminated signage will usually need listed building consent under the Planning (Listed Buildings and Conservation Areas) Act 1990 as well as advertisement consent, because fixings into historic fabric affect the building's special interest. And in a conservation area or an area of special control, several of the deemed consent classes are restricted, so a sign that would be automatically permitted elsewhere needs an express application.

Regulation 3 of the 2007 Regulations is worth reading once. It is short, and it is the reason a council cannot refuse your sign because the officer dislikes the brand colours.

Amenity and public safety, and nothing else

Amenity covers the visual effect on the character of the locality, including the building the sign is fixed to and the wider street. In a town centre with a coherent shopfront rhythm, an internally illuminated box fascia reads as an intrusion, while halo-illuminated individual letters usually do not. That distinction turns up in conservation area design guidance across the country, and it is the single most common reason a small retailer ends up reapplying.

Public safety covers the effect on people using the highway, railways, waterways and airfields. The highway authority is the consultee that matters here, and its objections are about distraction, confusion with traffic signals, and glare at a specific approach speed and angle. Where the display is near an aerodrome, a different analysis applies, and the issues are closer to those set out in our note on glint and glare assessment near an aerodrome.

Neither test allows a council to control the message. A sign with a political slogan and a sign advertising a sandwich are treated identically.

How luminance limits are set

The limits in general use come from professional lighting guidance rather than from the Regulations. The Institution of Lighting Professionals publishes maximum luminance values for illuminated advertisements, structured by the environmental zone of the location and by the area of the sign face. The zones run from E0, intrinsically dark areas such as a national park, through E1 for dark rural surroundings, E2 for low district brightness such as village and rural settings, E3 for suburban areas of medium brightness, to E4 for town and city centres with high district brightness.

The pattern is straightforward even without quoting figures. The darker the zone, the lower the permitted luminance, and above a certain sign area the permitted luminance drops again, because a large panel at a given brightness throws far more light at the observer than a small one. Ask your sign contractor for the specified luminance of the product in candelas per square metre, then check it against the values in the current guidance for your zone and sign size. If the contractor cannot give you a figure, that is itself a warning.

Two practical points. First, the zone is a judgement about the surroundings, not a designation you can look up, and an applicant and an environmental health officer can reasonably reach different views about whether a suburban parade is E3 or E2. Second, the stated output of a display is its maximum, and the relevant question at night is what it is dimmed to.

Digital displays, dwell times and movement

A digital display raises everything a static sign raises, plus change. Authorities commonly condition four things:

• a maximum luminance during daylight hours and a lower maximum after dark
• automatic dimming controlled by a photocell responding to ambient light, so the display adjusts rather than relying on a timer
• a minimum display time for each image, with no scrolling, fading, animation or video
• a fail-safe that defaults the display to blank if the control system fails

The minimum display time is the term to negotiate early, because it drives the commercial case for the screen. Highway authorities push for longer dwell times on the reasoning that a driver's attention is drawn by change rather than by brightness alone. There is no national figure, and the periods applied vary between authorities and between locations on the same road.

Where a display faces a signalised junction, expect a harder line. Objections there turn on the risk of a driver reading the display instead of the signal head, and mitigation usually means reorienting the screen rather than dimming it.

Conditions, and what to offer before you are asked

Consent for illuminated advertisements is routinely granted with conditions on hours of illumination, maximum luminance and, for digital displays, the control regime. Offering the conditions yourself, in the application, is the fastest route through.

A workable submission for an illuminated fascia and projecting sign contains elevations at a proper scale with dimensions, a specification giving the illumination method and maximum luminance in candelas per square metre, a note of the proposed hours of illumination tied to the trading hours, a statement identifying the environmental zone and justifying it, and a photograph of the existing frontage in context. Where the site is sensitive, a Lighting Assessment prepared against the relevant professional guidance saves an exchange of letters, and on or near a heritage asset a short Heritage Statement covering the effect on the building and the street will be expected.

Illustrative example: a takeaway on a suburban parade proposes an internally illuminated fascia and an illuminated projecting sign, with the parade treated as an E3 zone. The officer accepts the zone but conditions illumination to trading hours plus 30 minutes, requires the fascia to be halo-illuminated lettering on a non-illuminated background, and sets a maximum luminance by reference to the current professional guidance. Illustrative only, and outcomes vary by authority.

Where deemed consent stops

Schedule 3 to the 2007 Regulations grants deemed consent for defined classes of advertisement, which is why most shops do not apply for consent for a simple name board. The classes carry conditions and limitations on size, height above ground and illumination. Several of them do not extend to illuminated displays at all, and the standard conditions in Schedule 2 apply to every advertisement displayed under deemed consent, including a requirement that it is kept clean and tidy and does not endanger anyone using the highway.

A council can also serve a discontinuance notice to remove an advertisement displayed with deemed consent where it causes substantial injury to amenity or a danger to the public. That is the backstop for the sign that was lawful when installed and has become a problem since.

If you are unsure which route applies, ask the council's advertisement officer before ordering the sign. Sign contractors are not always reliable on consent, and the cost of removing an unlawful illuminated display falls on the occupier.

This is general guidance rather than legal advice. Check the position with your local planning authority or a qualified professional before relying on it.

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