Perceived adequacy of illumination, spatial brightness, horizontal illuminance and mean room surface exitance in a small office

116

This article discusses quantitative recommendations for road lighting as given in guidelines and standards, primarily, the amount of light. The discussion is framed according to the type of road user, the driver and the pedestrian, these being the user groups associated with major and minor roads, respectively. Presented first is a brief history of road lighting standards, from early to current versions, and, where known, the basis of these standards. Recommendations for the amount of light do not appear to be well-founded in robust empirical evidence, or at least do not tend to reveal the nature of any evidence. This suggests a need to reconsider recommended light levels, a need reinforced by recent developments in the science and technology of lighting and of lighting research. To enable improved recommendations, there is a need for further evidence of the effects of changes in lighting: This article therefore discusses the findings of investigations, which might be considered when developing new standards.

Section: Comparing Approachesmentioning

confidence: 99%

Road lighting research for drivers and pedestrians: The basis of luminance and illuminance recommendations

Fotios

Gibbons

2018

116

“…The author's discussions with several lighting professionals arrived at a reasonable consensus that the three levels of task illuminance in the third column, which cover the range commonly employed by regulators for specifying illuminances to be provided for general indoor lighting practice, could be expected to correspond with the PBI levels indicated. Duff et al 19,20 have reported a series of experimental studies conducted in both a viewing cabinet and a small office that found a linear relationship between subjects' assessments of spatial brightness and ambient illumination over an MRSE range of 25-100 lm/m 2 , and this provides the basis for the scale of MRSE levels indicated in the fourth column. Only the PBI-2 to PBI-4 values fell within the range of the experimental conditions, and the PBI-5 and PBI-6 levels are identified by asterisks as they are extensions of the experimental findings determined by multiplying the PBI-4 value by the same increments as occur for the E task values.…”

Section: Lpd Simulationmentioning

confidence: 97%

Making the switch from task illumination to ambient illumination standards: Principles and practicalities, including energy implications

Cuttle¹

2019

Self Cite

It has been proposed that general lighting practice should switch from specifying indoor illumination standards in terms of task illuminance to ambient illumination specified in terms of mean room surface exitance. The reasons for this proposal are reexamined and the energy implications are assessed. To enable comparison of equivalent levels of illumination, it was first necessary to establish mean room surface exitance levels that equate to task illuminance levels as being typical for similar applications. A simulation was developed using AGi32 lighting design software to determine lighting power density levels for providing equivalent illumination by three luminaire luminous flux distributions for three room shapes with three surface reflectance combinations. As anticipated, the downlight distribution was found to be the most efficient way of satisfying task illuminance criteria, but also it was found that uplighting achieves similar lighting power density levels for the equivalent mean room surface exitance criteria if room surface reflectances are reasonably high, indicating that the switch could be made without departing from the lighting power density limiting values currently proposed for efficient use of lighting energy. However, to base lighting standards on low lighting power density levels would have the effect of severely restricting options in lighting practice. Accordingly, a range of lighting power density levels is proposed for lighting standards that would eliminate inefficient use of lighting energy while permitting reasonable levels of design flexibility in lighting practice.

“…He developed procedures for measurement and calculation; 9 he compared the accuracy of alternative prediction formulae 10 and he conducted experiments which involved subjects making subjective assessments of their surrounding environments. 11,12 The outcomes of these experiments are examined in the following section and are shown to be particularly relevant to this paper.…”

Section: Duff's Researchmentioning

confidence: 99%

“…The first experiment involved subjects making brightness assessments while looking into a laboratory lighting booth, 11 and for the second experiment, they were seated in a small office and they assessed both brightness and illumination adequacy. 12 A feature of these experiments was the consistency with which the experimental conditions were maintained. For both experiments, the same group of 26 subjects was presented with 27 viewing situations, nine at each of three sittings.…”

Section: Duff's Researchmentioning

confidence: 99%

A fresh approach to interior lighting design: The design objective – direct flux procedure

Cuttle¹

2017

Self Cite

A new lighting design procedure is proposed based on how lighting influences the appearance of indoor spaces and their contents. Exitance is the measure of the density of luminous flux (lm/m2) exiting, or emerging from, a surface, and provides an effective basis for relating the quantity and distribution of lighting to peoples' assessments of its visual effects. The procedure guides users from identifying selected lighting design objectives relating to how peoples' assessments of appearance are affected by lighting, to developing a specification for the direct flux distribution that will optimally achieve those objectives. Applications can range from basic to complex. A selection of previously published lighting concepts is reviewed in the light of recently published research, and based on these concepts, the procedure takes the form of a downloadable spreadsheet that enables users to prioritise between efficient flux utilisation and achievement of design-oriented objectives. While it is recognised that more research is needed before the procedure could be adopted for general application, the aim of this paper is to demonstrate the opportunities offered by a practical alternative to current lighting practice.