The recommendations for good lighting give practical values for various lighting criteria, depending upon the application. The recommendations are drawn from a variety of documents, the principle documents being:

Section 4.1 Indoor workplaces
EN 12464-1:2002 Light and Lighting – Lighting of work places
– Part 1: Indoor work places and CIE S 008:2001

Section 4.2 Outdoor workplaces
EN 12464-2:2007 Lighting of work places
– Part 2 : Outdoor work places and CIE S 015:2005

Section 4.3 Sports
EN 12193: 2007 Light and Lighting – Sports Lighting

Section 4.4 Emergency
EN 1838:1999 and CIE S 020/E:2007 Emergency Lighting

Section 4.5 Roads
EN 13201 1-4 Road lighting practice

Section 4.6 Tunnel
CR 14380:2003 Lighting Applications – Tunnel Lighting

Note that these recommendations are based upon the European norms and local regulations may stipulate different values.

Whilst these limiting values may be considered to be the minimum design criteria additional factors should be taken into account to ensure a good lighting installation. Some of these factors are described in other sections of this book. The criteria used in the recommendations are defined below.

E_m This is the maintained average illuminance, that is the minimum value for average illuminance provided during the maintenance cycle of the installation.

E_min This is the minimum value of illuminance that is permissible within any calculation or measurement grid.

GR_L This is maximum value of glare rating that is permissible in any direction within any measurement or calculation grid.

L_m This is the maintained average luminance, that is the minimum value for average luminance provided during the maintenance cycle of the installation.

Ra This is the colour rendering index for a lamp and defines the ability of a lamp to show different colours correctly.

SR This is the surround ratio, which is a value used in the design of road lighting applications. It is the ratio of the average illuminance of a strip just outside the carriageway compared to the average illuminance of a strip just inside the carriageway

TI This is the threshold increment, which is a measure of the loss of visibility caused by the disability glare of the luminaires in an installation.

UGR_L This is the limiting maximum value of glare calculated by the unified glare rating method.

Ul This is the uniformity of illuminance along a line, being defined as the minimum illuminance value within line of measurement points divided by the average illuminance value of the line of measurement points (E_{min_line/}Em_line).

U_o This is the uniformity of illuminance across any calculation or measurement grid, being defined as the minimum illuminance value within a grid of measurement points divided by the average illuminance value of a grid of measurement points (E_min/E_m).