Steve Fotios

• PhD
• Professor of Lighting and Visual Perception at The University of Sheffield

Comparing the counts of cyclists travelling at specific times of day is one approach to measuring the impact of ambient light level. Here we investigate one source of variance in the magnitude of change seen in previous research—the choice of case and control hour. This was done through an analysis of cyclist flows using data from multiple automate...

Introduction Vulnerable road users (VRUs), such as pedestrians and cyclists, are disproportionately affected by road traffic crashes, resulting in casualties and short and long-term injuries (World Health Organisation, 2023). Many driver factors (e.g., age, vision problems, distraction) and environmental factors (e.g., limited lighting, infrastruct...

Road lighting should support the needs of pedestrians to make interpersonal evaluations after dark, for example, whether it feels safe to walk towards the person ahead or if avoiding action should be taken. In previous studies this has been investigated using a facial emotion recognition (FER) task, but using only full-face views of the person ahea...

In the day-dark approach to measuring the contribution of road lighting to pedestrian reassurance, reassurance is evaluated in daylight and after dark. In previous studies, the daylight and after dark evaluations were carried out at different times of day. Other factors, such as the presence of other people, are likely to vary with time of day, and...

It stands to reason that if people feel safe to cycle or walk at night, they will be more likely to choose to do so, so encouraging more active travel. Research has been looking at the role road lighting can play in this. This article discusses the steps taken to ensure the research is valid. Full text available here: https://flickread.com/edition...

Evidence about the relationship between lighting and crime is mixed. Although a review of evidence found that improved road / street lighting was associated with reductions in crime, these reductions occurred in daylight as well as after dark, suggesting any effect was not due only to changes in visual conditions. One limitation of previous studies...

Female pedestrians tend to report feeling less safe than do male pedestrians, and this difference is greater after dark than in daylight. A field study of pedestrian reassurance was conducted to test whether this was affected by the illuminance offered by road lighting. The results suggest that the male-female difference in reassurance ratings decr...

The objective of this presentation is to promote awareness of some of the difficulties found when measuring subjective evaluation of discomfort from glare, thus to encourage support for and participation in work to report on best practise when measuring discomfort from glare. Improving experimental design is a step towards resolving the disagreemen...

While lighting is expected to have some impact on alertness, previous research in the context of walking or driving in the evening did not reveal a significant effect. Those studies used lighting conditions similar to those considered acceptable for road lighting application. The null finding was tested in the current work by conducting an experime...

A large proportion of the sensory input to decision making is visual, suggested being more than 80% for driving. Risks associated with driving increases in the hours of darkness due to decreased visibility, and poor detectability of vulnerable road users especially in dark clothing. Combining this with driver distraction (engagement in activities n...

While the definition of reassurance highlights walking alone, in many studies of pedestrian reassurance the pedestrian is not alone but accompanied by other test participants and/or the experimenter. A field study of pedestrian reassurance was carried in residential roads with the 122 test participants allocated to conducting their evaluations eith...

This paper concerns the inclusion of cyclists in recommendations and standards for road lighting design. We use the results from eye tracking experiments to discuss cyclists’ gaze behaviour after dark to question the assumption that the needs of cyclists are co-incident with the needs of pedestrians. There is some suggestion that the greater propor...

Darkness discourages cycling. A major reason for this is perceptions of safety – cycling after dark feels more dangerous as it is more difficult to see hazards in the path, and the cyclist is less conspicuous to motorists. Are these perceptions justified? To find out we assessed the accuracy of such perceptions by analysing crash data from Great Br...

This research concerns the influence of electric lighting on user behaviour in public squares and whether differences in people’s use of the square can be observed between daylight and darkness. Previous research on pedestrians suggests that lighting can support human needs for reassurance, accessibility, comfort and pleasure. While these findings...

Odds ratios for the effect of ambient light level on cyclist numbers tend to reveal a variation between counters at different locations. We investigated reasons for this variation through analysis of cycle count data in two cities, Berlin (Germany) and Birmingham (UK). For Berlin, there was a significant increase in the odds ratio with increasing d...

Comparing the counts of events occurring at different times of day is one approach to measuring the impact of ambient light level on events such as crime, road traffic collisions and travel flows. We investigated the choice of case and control hours on the outcome of analysis of cyclist flows for two cities, Arlington (VA, USA) and Birmingham (UK)....

Over the past 25 years, distracted driving and driver inattention have been one of the main risk factors for road traffic safety. Previous research has shown that increased cognitive load from non-visual activities take our mind off the driving task, by engaging our working memory resources. Studies have shown that engagement in these tasks results...

Over the past 25 years, distracted driving and driver inattention have been one of the main risk factors for road traffic safety. Previous research has shown that increased cognitive load from non-visual activities take our mind off the driving task, by engaging our working memory resources. Studies have shown that engagement in these tasks results...

Over the past 25 years, distracted driving and driver inattention have been one of the main risk factors for road traffic safety. Previous research has shown that increased cognitive load from non-visual activities take our mind off the driving task, by engaging our working memory resources. Studies have shown that engagement in these tasks results...

A laboratory experiment was conducted to investigate the alerting effect of light under lighting conditions typical of road lighting. After a 2-h adaptation period, under lighting representing a domestic interior, participants were exposed for a further hour to one of four lighting conditions, with illuminance at the eye and spectral power distribu...

After dark, pedestrians may experience discomfort from glare caused by outdoor lighting. While several models for measuring discomfort have been proposed, there is no consensus as to which model should be used. The performances of different models were investigated using datasets from four independent studies, comparing the degree of association be...

Cycling has a range of benefits and should be encouraged, but darkness may put people off from cycling due to reductions in visibility, road safety and personal security. We summarise previous work that consistently demonstrates how darkness reduces the number of people cycling after dark, after accounting for confounding factors such as time of da...

Cultural factors in Libya (and other Muslim countries) require female privacy to be maintained. Outside the home, females must wear clothing that reveals only the face and hands. When inside the home and located near windows, a similar degree of clothing cover or window treatment is required. This reduces exposure to natural daylight, with resultan...

This paper explores social interaction in local public squares under different lighting conditions. At its best public squares are social spaces that engender a sense of belonging, increase the quality of life and wellbeing of individuals. It is proposed that outdoor lighting would be essential to the use of the public realm after dark, but empiric...

Pedestrians need to be able to evaluate other people to support their feeling of safety. While past studies have thus investigated the degree to which road lighting supports facial identity and facial emotion evaluations, it is not yet known whether the face is the most important visual cue. Following a pilot study that indicated the importance of...

This paper explores social interaction in local public squares under different lighting conditions. At its best public squares are social spaces that engender a sense of belonging, increase the quality of life and wellbeing of individuals. It is proposed that outdoor lighting would be essential to the use of the public realm after dark, but empiric...

The optimal illuminance from road lighting for pedestrian reassurance after dark is that beyond which further increase in illuminance has no significant effect on reassurance. Previous studies have not revealed a precise estimate of optimal illuminance. The current study investigates the use of segmented regression for defining optimal illuminance,...

This study concerns road lighting for pedestrians. Many experiments have been conducted to determine how changes in lighting affect the ability to make interpersonal evaluations, usually considering variations in light level or light spectrum. Here, we consider an alternative approach, predicting performance using an existing model, Relative Visual...

Previous studies have suggested mixed results about the effect of road lighting on crime. One potential explanation is that the effect of lighting, if any, varies with the type of crime. This was tested through analysis of the effect of change in ambient light level on crimes recorded in 11 cities in the USA for the 10-year period 2010–2019. The re...

Ambient light level, one of the items recorded by police investigating a road traffic collision (RTC) was previously suggested to be incorrectly recorded in 5%–15% of cases. Significant erroneous categorisation of ambient light level, as suggested by the latter estimate, may lead to incorrect conclusions being drawn about the impact of light on RTC...

Previous studies have gained data from automated counters to compare the influence of ambient light level on the numbers of people walking and cycling. This paper reports an exploratory study using instead in-person counting, the advantage being that the apparent age and gender of each pedestrian and cyclist can also be recorded. The analysis compa...

While the de Boer scale is widely used to measure discomfort from glare, commonly in studies of pedestrian-scale outdoor lighting, its design has several problems that lead to noise in the data and in turn to continued disagreement about the prediction of discomfort. We propose here a two-step alternative approach for rating discomfort from glare....

While some previous research suggests that conversing with passengers is the most prevalent in-vehicle distraction while driving, others have concluded instead that it is mobile phone use. One possible explanation for these differences is that distraction prevalence varies with road type. To test this proposal the current study investigated the pre...

Cultural factors in Libya (and other Muslim countries) require female privacy to be maintained. Outside the home, females must wear clothing that reveals only the face and hands. When inside the home and located near windows, a similar degree of clothing cover, or, window screening, is required. This reduces exposure to natural daylight, with resul...

Pedestrians and motorcyclists are vulnerable road users, being over represented in road traffic collisions (RTCs). One assumed benefit of road lighting is a reduction in RTCs after dark by countering the impairment to the visual detection of hazards that occur after dark. One way to optimise the use of road lighting is to light only those sections...

In research of lighting for pedestrians, many experiments have been conducted to determine how changes in lighting affect the ability to make interpersonal evaluations. Here we consider an alternative approach, predicting performance using a model - Relative Visual Performance. The results show that face evaluation ability is affected by adaptation...

In outdoor environments after dark, pedestrians may experience discomfort from road lighting. Previous studies have therefore developed models to predict discomfort from glare in pedestrian applications. However, the performance of these models has not been comprehensively assessed, and measurement challenges arise in field evaluations. This paper...

In subsidiary roads, lighting is installed to meet the needs of pedestrians after dark for safety and their feeling of safety. One aspect is the need to evaluate other people to inform the approach-or-avoid decision. To investigate how changes in lighting matter for this task, we first need to know where people tend to look. Much past work assumes...

A recent study investigated the influence of lighting on crime by considering the effect of change in ambient light level on crimes recorded in three US cities for the ten-year period 2010 to 2019. The results suggested a significant increase in robbery after dark, but did not suggest significant change in for any other type of crime. The current s...

Cycling has a range of benefits and should be encouraged, but darkness may put people off from cycling due to reductions in visibility, road safety and personal security. We summarise analyses of observational data to confirm the negative impact darkness has on cycling rates. Using a Case / Control method that accounts for confounding factors such...

This article investigates the effect of ambient light level on traffic flow for different types of road user—pedestrians, cyclists, and drivers of motorized vehicles—using counts of traffic flow recorded by automated counters. Previous analyses have focused only on pedestrians and/or cyclists, in Arlington, Virginia (U.S.) and Birmingham (U.K.). Th...

The influence of lighting on crime was investigated by considering the effect of ambient light level on crimes recorded in three US cities for the ten-year period 2010 to 2019. Crime counts were compared for similar times of day, before and after the biannual clock change, therefore employing an abrupt change of light level but without an obvious i...

Obstacle detection and facial emotion recognition are two critical visual tasks for pedestrians. In previous studies, the effect of changes in lighting was tested for these as individual tasks, where the task to be performed next in a sequence was known. In natural situations, a pedestrian is required to attend to multiple tasks, perhaps simultaneo...

It is expected that the detection of peripheral objects, a key visual task for safe driving, is affected by cognitive distraction, by observer age and by the manner in which action is undertaken following detection. An experiment was conducted to measure these effects, using a fixation cross and peripheral target discs displayed on a screen. The ex...

Design criteria for lighting in subsidiary roads usually include a minimum average horizontal illuminance, widely assumed to be the arithmetic mean illuminance. Analyses of the illuminance distributions over thirty road sections shows that the distributions are not normal and hence the median is more appropriate than the arithmetic mean as a measur...

The effect of ambient light level on road traffic collisions (RTCs) involving a motorcycle was investigated. Data were drawn from the STATS19 database of UK reported RTCs for the period 2005–2015. To isolate the effect of ambient light (daylight vs darkness) an odds ratio was used to compare RTCs at specific times of day in the weeks either side of...

This article presents a review of the methods used for subjective evaluation of discomfort from glare, focusing on the two procedures most frequently used in past research – adjustment and category rating. Evidence is presented to demonstrate that some aspects of these procedures influence the evaluation, such as the range of glare source luminance...

Cycling has a range of benefits as is recognised by national and international policies aiming to increase cycling rates. Darkness acts as a barrier to people cycling, with fewer people cycling after-dark when seasonal and time-of-day factors are accounted for. This paper explores whether road lighting can reduce the negative impact of darkness on...

A recent paper proposed a more precise approach for investigating the impact of ambient light (daylight versus after dark) on road traffic collisions. The present paper first repeated that analysis of road traffic collisions in the UK to test reproducibility; it then extended the analysis to determine whether the greater precision affected the outc...

There is a body of research showing how changes in lighting conditions affect hazard detection in the context of driving after dark. There is a separate body of research showing that driving is impaired by distraction. The two have yet to be integrated: this is critical for lighting design recommendations because giving consideration to distraction...

Cycling has a range of benefits as is recognised by national and international policies aiming to increase cycling rates. Darkness acts as a barrier to people cycling, with fewer people cycling after-dark when seasonal and time-of-day factors are accounted for. This paper explores whether road lighting can reduce the negative impact of darkness on...

This paper is a discussion of the factors that might be used to establish a suitable light level for subsidiary roads where the target users are pedestrians. The weighting parameters used in the Commission Internationale de l'Eclairage document CIE115:2010 to discriminate between the six levels of the P-series of lighting classes are questioned. Li...

Category rating is a procedure commonly used to evaluate visual discomfort due to glare. One recommended step for good practise in a category rating procedure is to use a pre-trial demonstration (PTD) of the range of stimuli to be experienced. However, PTD have rarely, if at all, been used in past research on discomfort glare. In this study, two ex...

Lighting can play an important role in encouraging cycling after-dark and making it safer. This paper describes ongoing research to establish a basis for design guidance when lighting for cyclists. Comparison of cyclist counts and estimated illuminance levels suggest a small increase in illuminance after-dark can significantly reduce the negative i...

Reassurance describes the degree of confidence a pedestrian might have to walk, a critical concern where there are national plans to promote walking rather than driving for local journeys. This paper describes a field study carried out to measure the reassurance benefit of lighting using the day-dark method. The results suggest that reassuranc is b...

To establish optimal lighting for inter-personal evaluations between pedestrians it is desirable to know what visual cues are used. An experiment was conducted to test two proposals. One, the widely made assumption (in lighting research) that the face is an important cue. Two, the hierarchy of factors proposed by a lighting designer. This was inves...

Detecting pavement irregularities that might lead to a fall if not seen in sufficient time is one of the critical visual tasks of pedestrians. Experiments have been conducted to determine how the detection of peripheral objects, at mesopic light levels, is affected by light level and spectrum, leading to proposals for new guidance. As with all expe...

For pedestrian lighting, CIE115:2010 specifies six classes of a verage and minimum horizontal illuminance (the P classes) with less specific proposals to consider colour rendering index and semi-cylindrical illuminance if there is a need to recognise pedestrians. This article is a discussion of design metrics: are these appropriate recommendations?

Applied lighting research is inherently interdisciplinary. Any one study in which investigators seek to understand the effects of light may involve expertise drawn from fields as varied as psychology, physiology, photobiology, vision science, engineering, physics, horticulture, and architecture. Despite differences in the specifics of research meth...

Luminance adjustment is widely used to evaluate discomfort due to glare. This paper reports an experiment conducted to investigate two factors of the luminance adjustment procedure, stimulus range bias and direct vs indirect control. Stimulus range bias describes the influence on subjective evaluations of the range of stimuli available to the test...

Previous work investigating how lighting enhances peripheral detection for pedestrians has tended to consider only raised hazards and lighting from a directly overhead source. An experiment was conducted to determine the extent to which variations in these parameters would influence the recommendations for optimal lighting. The results did not sugg...

Do responses gained using category rating accurately reflect respondents’ true evaluations of an item? “True” in this sense means that they have a real opinion about the issue, rather than being compelled by the survey to speculate an opinion, and that the strength of that opinion is faithfully captured. This article describes some common issues th...

To determine mesopic luminance for a given photopic luminance and scotopic/photopic (S/P) ratio, the Commission Internationale de l’Eclairage (CIE) recommended system utilizes an equation. Whilst being accurate, it requires several iterations to achieve a stable result and requires the use of an adaptation coefficient. This article proposes an alte...

The scotopic/photopic ratio (S/P) is a parameter that may be considered in the design of road lighting. This paper compares the S/P ratio and correlated colour temperature (CCT) for 297 light source spectra identified in IES Technical Memorandum TM-30-15 to test the assumption that higher S/P ratios demand higher CCTs. The results suggest that, for...

This article concerns discomfort due to sources of glare in the peripheral visual field. A visual task is needed to maintain foveal fixation at a known location and in past studies the tasks have ranged from a simple fixation mark to a task requiring greater cognitive attention such as reading. It was hypothesized that these different approaches to...

A field study was conducted to investigate how changes in illuminance affect pedestrian reassurance when walking after dark in an urban location. The field study was conducted in daytime and after dark in order to employ the day-dark approach to analysis of optimal lighting. The results suggest that minimum illuminance is a better predictor of reas...

Hopkinson’s multiple criterion scale is widely used to investigate the subjective degree of discomfort due to glare. Using an adjustment procedure, glare source luminance is adjusted to reveal four levels of discomfort, typically: just imperceptible, just acceptable, just uncomfortable, and just intolerable. In many studies, observers are instructe...

Application of the Commission Internationale de l’Eclairage system for mesopic photometry requires that an estimate is made of the observers’ state of luminance adaptation. This paper addresses an assumption made when estimating background luminance, a component of adaptation luminance. Specifically, using spatial sampling of the visual field we co...

One of the aims of outdoor lighting in public spaces, such as pathways and subsidiary roads, is to help pedestrians to evaluate the intentions of other people. This paper discusses how a pedestrians' appraisal of another persons' intentions in artificially lit outdoor environments can be studied. We review the visual cues that might be used, and th...

Many studies have used surveys to investigate the reactions to changes in lighting from people who walk or cycle. An alternative approach is to use objective data, specifically the number of pedestrians and cyclists present under different lighting conditions. Such data have been reported previously using a daylight savings transition approach. Thi...

Luminance adjustment is a procedure commonly used to evaluate discomfort glare and the results from adjustment experiments form the basis of some recommendations for limiting its occurrence. There are, however, strong reasons to expect that settings made using adjustment are unintentionally influenced by extraneous variables. This paper discusses b...

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...

Previous research suggests darkness increases the risk of a collision involving a pedestrian and the severity of any injury suffered. Pedestrian crossings are intended to make it safer to cross the road, but it is not clear whether they are effective at doing this after-dark, compared with during daylight. Biannual clock changes resulting from tran...

The presence of fog leads to an increase in road traffic accidents. An experiment was carried out using a scale model to investigate how the detection of hazards in peripheral vision was affected by changes in luminance (0.1 cd/m² and 1.0 cd/m² road surface luminance), scotopic/photopic (S/P) ratio (0.65 and 1.40) and fog density (none, thin and th...

An experiment to investigate peripheral detection performance during a driver’s transition between lit and unlit sections of road was undertaken. The results suggest that when a driver moves from a lit to an unlit section of road their detection performance decreases almost immediately to that expected for the conditions of the unlit section and th...

This article proposes a methodology, via a case study, to address the principles of Cost Benefit Analysis (CBA), applied to energy efficiency in social housing. In Northwest Mexico (NWM), comfort in Summer cannot be achieved without mechanical cooling; the hot-dry climate, combined with poorly designed dwellings, results in large cooling loads. Hav...

Daylight factor has long been the predominant metric to evaluate daylight performance. Recently, the profession has moved toward annual dynamic daylight metrics such as useful daylight illuminance and daylight autonomy, which are based on absolute values of time varying daylight illuminance for a period of full year. As opposed to static daylight m...

This article reports a novel procedure used to investigate whether ambient light conditions affect the number of people who choose to walk or cycle. Pedestrian and cyclist count data were analysed using the biannual daylight-saving clock changes to compare daylight and after-dark conditions whilst keeping seasonal and time-of-day factors constant....

Local authority lighting engineers have a responsibility to optimise the energy used by road lighting, to meet budgets and to meet environmental targets. Reducing the provision of road lighting can, however, lead to public criticism - articles in the Lighting Journal have shown part-night switch-off blamed for a fall (Nov, 2015, p4), for death from...

Tony Price and Steve Fotios point out that while road lighting can be a significant counter measure to accidents, and that higher levels might help, the presence of road lighting does not guarantee all accidents will be avoided.

Semi-cylindrical illuminance has been promoted as a better measure for lighting design than vertical illuminance. Professor Steve Fotios is unconvinced

An experiment was carried out to investigate how contrast threshold for target detection is affected by the presence of glare and by extraneous light sources using the method of ascending limits. The target was located at either a foveal or a peripheral (10° right) location, glare was adjacent to the foveal location, simulating the headlamps of an...

How we look at other people may affect conclusions drawn about the effect of changes in lighting when this task needs to be done after dark. This paper reports further analysis of the distance and duration of fixation on other pedestrians, updating a previous review by considering a greater number of fixations and by examining the influence on thes...

This paper investigates the illuminance needed to detect trip hazards for pedestrians walking after dark. In previous work, it was assumed that the critical obstacle height is 25 mm: further review of accident data and foot clearance data suggests instead that 10 mm is the critical height. Eye tracking records suggest a tendency for obstacles to be...

A recent article (Peña-García et al., 2015) presented conclusions regarding the benefits of road lighting for pedestrians. Here it is demonstrated that those conclusions were drawn from incomplete evidence, in one case because the experimental designs leads only to a trivial solution and in a second case because of an incomplete search of the liter...

Facial emotion recognition has been used as a representative pedestrian activity in studies examining the effect of changes in road lighting. Past studies have drawn conclusions using results averaged across performance with the six universally recognised expressions. This paper asks whether expression choice matters. A reanalysis of past data for...

The first part of this analysis reveals a tendency to associate the perceived quality of road lighting with perceived safety – people think they will feel safer in an area that they consider to be well-lit rather than badly-lit or unlit. But, for a person who already feels safe, improved lighting has little benefit. The final part demonstrates, how...