Article

Relationship of Vertical Illuminance to Pedestrian Visibility in Crosswalks

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Abstract

Twenty-six participants evaluated a series of crosswalk lighting designs by visually detecting objects within each crosswalk location. The research was performed on a closed test track under nighttime conditions while driving a Sport Utility Vehicle (SUV) with regular halogen headlamps. The conditions presented to each participant included varying illuminance levels (6, 10, 20, and 30 lux), varied luminaires (High Pressure Sodium (HPS), Metal Halide (MH)) and different object types (pedestrian and surrogate objects). The participant was asked to detect objects within each crosswalk location when they were confident there was an object present. The presentation of objects was varied to diminish expectation effects. The results indicated that object detection distances varied based on illuminance level, luminaire type, and object type. Object detection distance for the HPS was greatest at 30 lux and for MH at 20 lux. However, these results were moderated based on clothing color of the object. When object color was taken into consideration, pedestrians in white clothing were identified earlier under the HPS lighting condition at 20 lux. Under the MH configuration, denim-clothed objects were detected earlier compared to black-clothed objects, especially at a 20 lux lighting level. The results indicate crosswalk lighting levels provide adequate object lighting at 20 lux. Furthermore, pedestrians dressed in white clothing have superior detection distances compared to other object types.

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... Visual performance plays a critical role in nighttime driving because it affects the speed and accuracy of performance on the visual component of a task. Detection distance of objects (like pedestrian, targets, et cetera) is a commonly used measure of visual performance in nighttime roadway visibility research [Bhagavathula and Gibbons 2013;Edwards and Gibbons 2008;Hills 1975;Janoff 1993;Shinar 1985;Zwahlen and Schnell 1999]. The presence of lighting and an increase in lighting level greatly increase the accuracy and speed with which information can be extracted from the environment and have been found to increase visual performance [Boyce 1973;Eloholma and others 2006;Rea 2000;Terry and Gibbons 2015;Van Bommel and Tekelenburg 1986]. ...
... The second was to determine what lighting levels, perhaps specific to each lighting configuration, support the best visual performance. It was hypothesized that (1) intersection lighting configurations would differ in visual performance measurements, because different configurations affect object contrast, which, in turn, influences visual performance [Edwards and Gibbons 2008;Hills 1975], and (2) the benefit of increasing illuminance on visual performance will decrease (or plateau) at higher illuminance, consistent with Adrian's [1989] model and the RVP model [Rea and Ouellette 1991]. Results from this work were intended to facilitate development of intersection lighting design standards (especially for those intersections located in isolated/rural areas) that will increase driver visual performance and consequently reduce nighttime crashes. ...
... Generally, the visibility of objects at nighttime depends on their contrast with the relevant background [Edwards and Gibbons 2008;Pretto and Chatziastros 2006]. With respect to intersection, target contrasts are affected by the lighting configuration (part of the intersection illuminated) and the headlamps of the vehicle. ...
Article
Nighttime crashes at intersections present a major traffic safety issue in the United States. Existing approaches to intersection lighting design do not account for a driver’s visual performance or the potential interactive effects of vehicle headlamps and roadway lighting. For effective design lighting at intersections, empirical research is required to evaluate the effects of lighting configuration (part of the intersection illuminated) and lighting levels on nighttime driver visual performance. The current study had two goals: First, to quantify visual performance in three lighting configurations (illuminating the intersection box, approach, or both) and second, to determine what lighting levels within each lighting configuration support the best visual performance. The study involved a target detection task completed at night on a realistic roadway intersection. Illuminating the intersection box led to superior visual performance, as indicated by longer target detection distances, fewer missed targets, and more targets identified within a safe stopping distance. For this lighting configuration, visual performance plateaued between 7 and 10 lx of mean intersection illuminance. These results have important implications for the design of intersection lighting at isolated/rural intersections, specifically that illuminating the intersection box is an effective strategy to increase nighttime visual performance for a wider range of driver ages and could also be an energy-efficient solution.
... Researchers [59]- [62] identified additional lighting at pedestrian crossings as one of the most effective actions to improve the safety and visibility of pedestrians. Higher illuminance levels at such crossings can lead to a dual goal: to signal to drivers the presence of crossing and pedestrians and to persuade the pedestrian to use the crossing point. ...
... Higher illuminance levels at such crossings can lead to a dual goal: to signal to drivers the presence of crossing and pedestrians and to persuade the pedestrian to use the crossing point. The relationship between the vertical illuminance levels and pedestrian visibility at a crosswalk is investigated in references [61], [62]. The results point out that vertical illuminance values of 20 lux, measured at the height of 1.5 m from road level, can significantly increase pedestrian visibility. ...
Thesis
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Immersive virtual reality (IVR) represents one of the most promising technological aids in the development of a functional lighting design, especially when considering different points of view as users’ satisfaction. Nowadays, immersive virtual reality is one of the new technologies with a wide range of applications. In particular, immersive virtual reality can play an important role in the lighting design, thanks to its ability to allow for a quick assessment between different design choices based on spaces, colors and light. However, the IVR has to guarantee a correct reproduction of light behavior from photometric and visual points of view, in order to be effectively used for lighting analysis. The main outcomes can be related to the: i) methodology to use Unreal Engine 4.22 as a tool for lighting applications, allowing correct reproduction of artificial light distribution in the game engine by identifying and properly setting a restricted set of parameters and ii) investigated subjective and objective visual responses and participants' interaction with the virtual environment based on measurements of perceived presence. In case after the download you are interested in the methodology and some results, you are kindly requested to provide these citations: Scorpio, M., Laffi, R., Teimoorzadeh, A., Ciampi, G., Masullo, M., & Sibilio, S. (2022). A calibration methodology for light sources aimed at using immersive virtual reality game engine as a tool for lighting design in buildings. Journal of Building Engineering, 48 doi:10.1016/j.jobe.2022.103998 Scorpio, M., Laffi, R., Teimoorzadeh, A., & Sibilio, S. (2021). Immersive virtual reality as a tool for lighting design: Applications and opportunities. Paper presented at the Journal of Physics: Conference Series, , 2042(1) doi:10.1088/1742-6596/2042/1/012125 Scorpio, M., Laffi, R., Masullo, M., Ciampi, G., Rosato, A., Maffei, L., & Sibilio, S. (2020). Virtual reality for smart urban lighting design: Review, applications and opportunities. Energies, 13(15) doi:10.3390/en13153809
... Present recommendations for lighting pedestrian crosswalk areas are mainly based upon horizontal illuminance levels (2,3). Newer recommendations, building upon recent research (4)(5)(6)(7), utilize vertical illuminance because the vertical surfaces of pedestrians that drivers see are more important to illuminate than horizontal roadway surfaces. Bullough et al. (8) recently proposed a novel bollard lighting system for crosswalks that provides vertical illuminance along the crosswalk boundary while minimizing the amount of illumination on the ground in front of and behind the crosswalk. ...
... In addition, the salience of different parts of a moving pedestrian could change as a pedestrians traverses a crosswalk. Undoubtedly, motion would assist in detecting pedestrians, as described by Gibbons and colleagues (6,7) in their studies also using static visual stimuli. Differences among lighting configurations might be larger or smaller than those found in the present study, but there is no reason to expect the relative effectiveness of the configurations to differ in more realistic conditions, as confirmed by visual comparisons of real-world crosswalk lighting that were conducted by Bullough et al. (8). ...
... Researchers [46][47][48][49] identified additional lighting at pedestrian crossings as one of the most effective actions to improve the safety and visibility of pedestrians. Higher illuminance levels at such crossings can lead to a dual goal: to signal to drivers the presence of crossing and pedestrians and to persuade the pedestrian to use the crossing point. ...
... Higher illuminance levels at such crossings can lead to a dual goal: to signal to drivers the presence of crossing and pedestrians and to persuade the pedestrian to use the crossing point. The relationship between the vertical illuminance levels and pedestrian visibility at a crosswalk is investigated in references [48,49]. The results point out that vertical illuminance values of 20 lux, measured at the height of 1.5 m from road level, can significantly increase pedestrian visibility. ...
Article
Full-text available
More and more cities are evolving into smart cities, increasing their attractiveness, energy efficiency, and users’ satisfaction. Lighting systems play an important role in the evolution process, thanks to their ability to affect city life at night along with people’s mood and behaviour. In this scenario, advanced lighting design methods such as virtual reality (VR) became essential to assess lighting systems from different points of view, especially those linked with the city users’ expectations. Initially, the review highlights a list of objective and subjective parameters to be considered for the lighting design of three main city areas/applications: roads, green areas and buildings. Besides, the state-of-art in using VR for outdoor lighting design is established. Finally, the Unreal game engine is used to analyse the ability of VR to take into account the lighting parameters, not yet investigated in current literature and to highlight the VR potential for augmenting lighting design. The results confirm the benefit of using VR in lighting design, even if further investigations are needed to establish its reliability, especially from the photometrical point of view.
... Edwards measured detection distances of pedestrians under different levels of vertical illuminance reported that increasing the vertical illuminance on pedestrians increases the distance at which drivers can detect them. 26 All the above-mentioned research used fixed overhead lighting to illuminated pedestrian crosswalks, some of the recent research in pedestrian visibility used to bollard type lights to illuminate pedestrian crosswalks. A recent study exploring different ways to illuminate crosswalks for potential improvements in pedestrian visibility and safety. ...
... For example, a study used conventional overhead lighting for illuminating crosswalks reported that a vertical illuminance level of 20 lux at a height of 1.5 meters (5 feet) from the road surface resulted in good driver visual performance at midblock crosswalks. 26 Another study using bollard lighting system to illuminate a crosswalk reported that a vertical illuminance of at least 10 lux on the pedestrian at a height of 0.9 meters (3 feet) is required to increase contrast and thereby visibility. 30 It is important to note that pedestrian visibility in bollard based lighting has never been directly compared to overhead lighting in realistic roadway conditions where the drivers approached the crosswalk at speed. ...
Technical Report
Nighttime safety continues to be a major concern for transportation agencies across the country. Roadway lighting has been widely used as a countermeasure for nighttime crashes. However, safetyengineers and researchers frequently lack effective tools when determining exactly how lighting should be optimized to maximize safety while conserving energy. This project involved an extensive effort to investigate traffic safety lighting impacts at intersections. Based on the results, the project identified optimal lighting levels for different types of intersections and developed guidelines to facilitate lighting needs analysis and design at the Virginia Department of Transportation. During this study,a crash analysis showed a 2.9% reduction in night-to-day crash ratio for each 1-lux increase of minimum illuminance at intersection boxes. Additionally, the project team found a benefit-cost ratiobetween 2.6 and 5.6for unsignalized intersections and between 2.8 and 7.9 for signalized intersections, assuming one injury nighttime crash per year at such locations and depending on whether existing poles can be used.
... Overhead lighting also increases the distance at which pedestrians are detected (Bhagavathula, et al., 2012;Edwards & Gibbons, 2008). Presence of overhead lighting not only decreases the risk of pedestrian accidents (Wanvik, 2009), but also reduces the number of nighttime pedestrian crashes (Pegrum, 1972;Polus & Katz, 1978). ...
... From the results of this study motion seems to draw more attention than expectancy when it comes to detecting new objects at nighttime on roadways. The results of this study reinforce the safety benefits of overhead lighting (Edwards & Gibbons, 2008;Polus & Katz, 1978;Wanvik, 2009) and decrease in visual performance of older drivers (Owens, Wood, & Owens, 2007;Wood, Tyrrell, & Carberry, 2005). Finally, the results also confirm existing research that drivers tend to detect human form (static or moving) with relative ease when compared to other inanimate objects (Balk, et al., 2008;Johansson, 1973;Owens, et al., 1994). ...
Article
More than half of the pedestrian fatalities occur at night. It is important to understand the factors that lead to pedestrian detection for designing and implementing effective countermeasures in order to reduce pedes-trian fatalities. Research has shown that expectancy, motion and overhead lighting affect pedestrian visibil-ity. This goal of this study is to understand the combined effect of these three factors on nighttime visibil-ity. Twenty four participants were recruited to drive on a test track under different conditions of expectancy and overhead lighting. The participants were asked to identify static and moving objects. The results showed that as the level of expectancy increases the detection distances also increase. Moving objects were detected from farther than static objects and presence of overhead lighting also increased the detection dis-tances. Motion tends to draw more attention than expectancy when detecting new objects. These results have implications in the areas of pedestrian safety, novice driver training and work zone safety. They also reiterate the safety benefits of providing overhead lighting at high pedestrian-vehicle conflict areas.
... Given the fact that the luminance of vehicle headlights can be more than 100 times the road surface luminance, 7 the presence of glare from oncoming car headlights has a direct effect on drivers' visual performance. Bullough and Van Derlofske 8 found that this glare increased reaction time. ...
... The detection distance was used as a measure of visibility by Edwards and Gibbons. 7 The experiment was divided into two parts: Part A dealt with an unlit street and focused on the effect of oncoming car headlights on the detection distance. Part B dealt with a lit street and focused on the effect of changing the street lighting. ...
Article
This study examines the effect of different types of lamps on pedestrian night time visibility. Detection distance was used as a measure of visibility. The detection distance was measured in the presence and in the absence of on-coming car headlamps in an unlit street. Subsequently, the street was lit using metal halide, high-pressure sodium or LED luminaires. A pedestrian who changed his clothing colour randomly was used as a target. The results showed that the detection distance on the unlit road was 52% shorter in the presence of on coming car headlamps than when the oncoming car headlamps were off. A person wearing black clothing was harder to see and their mean detection distance was 60% less than when the observer was not dazzled by the oncoming car headlights. When the street was lit, the detection distance was doubled. The mean detection distance using LED lamps was statistically similar to that obtained using metal halide lamps, both of which were better than the detection distance obtained under high pressure sodium lighting.
... 186 US guidance 4 suggests instead to use vertical illuminances (at 1.5 m height), these being 10 lux and 2 lux for areas of high and medium pedestrian conflict, these data as determined from test track studies. 187 A limitation of specifying a single value of illuminance is that it does not account for local conditions: it may be too low if visual adaptation is raised by extraneous local lighting or by a generally high level of road lighting. In the UK, TR12 of the Institution of Lighting Professionals overcomes this by recommending an illuminance relative to that of the road in which the crossing is placed, which is itself chosen partly with consideration to the surrounding environment. ...
Article
Full-text available
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.
... (Adrian, 1989;Farber, 1988;Muttart, et al., 2013). Also, as lighting improved, so did driver performance (Adrian, 1989;Farber, 1988;Edwards, Gibbons, 2009). The exception to this occurred when the lighting caused glare (or veiling luminance). ...
Article
Full-text available
Over the years, in a night time driving scenario, expectancy has been linked with faster night time recognition. This study tries to evaluate the ability of observers to identify illuminated objects on the road in the absence of an associative pattern. In this study 47 of 60 participants did not respond to a light source that was in the drivers’ travel lane ahead. Of those who did not respond to the light when directly ahead, 64% indicated that had seen it beforehand. When the light was 2 meters to the drivers’ right, 33% that saw the light failed to respond. All of the drivers who saw the light before striking it claimed that they thought it was off the road until too late. When the drivers did not know what the light source was, they could not decipher where the light was. However, once aware of the presence of the light the average recognition distance improved 192 meters (632 feet) with 100% recognition. These results fit well with the SEEV search model and an Information Theory approach to driver expectancy. Previous claims that the difference between expected and unexpected driver responses is a 2 to 1 ratio was not supported by this research.
... Research by Gibbons and Hankley [7], showed that 20 lx was already sufficient to spot objects at pedestrian crossings. In a later study, Edwards and Gibbons [8] analyzed the effect of lamp spectral distributions on pedestrian visibility. They performed field tests using a passenger car and, based on an analysis of object detection distances, showed that 20 lx with metal-halide lamps and 30 lx with high-pressure sodium lamps provided sufficient illuminance levels for spotting objects. ...
Article
Full-text available
The pedestrian is the least protected road user. A large number of accidents involving pedestrians occur at pedestrian crossings. Bad lighting or a complete lack of it is one of the causes of accidents in these places. Currently, there are no uniform requirements in Europe for the lighting of pedestrian crossings. Each country is trying to create its system of requirements and assessment of lighting of pedestrian crossings. Measurement procedures and required lighting parameter values often vary significantly across countries. This paper discusses the results of measurements carried out at selected pedestrian crossings using two different measurement grids. The lighting quality at the tested crossings has been assessed based on the lighting requirements in force in two EU countries. In addition, we present the results for the illuminance contrast of a measurement board, representing the silhouette of a pedestrian on a crossing, with the background. Based on the determined contrast, we attempted to verify the lighting conditions using an evaluation system described in the literature, which employs fuzzy logic algorithms.
... The locations that were used for the present evaluation were relatively dark at the time of the demonstrations. At locations with higher light levels, and particularly those where pole-mounted luminaires are located 10 to 20 feet ahead of the crosswalk to help provide increased positive contrast (Freedman et al., 1975;Hasson et al., 2002;Edwards and Gibbons, 2008;Bullough et al., 2010Bullough et al., , 2012, the incremental benefit of the bollard lighting system on visual performance could be smaller. ...
... Detection distance has been commonly used as a measure of visual performance in nighttime roadway visibility research (10)(11)(12)(13)(14). Detection distance is the distance at which participants detect the worker in the work zone. ...
Article
Nighttime crashes at work zones are major concerns for construction workers and motorists. Although in a majority of the U.S. states, department of transportation specifications for work zone lighting mention that contractors should reduce glare for workers and drivers, only two states advocate detailed specifications like light positions, orientation, and light levels. Although some studies have examined the impact of glare from work zone lights on workers and others have calculated veiling luminance levels for drivers in the work zone, the effect of work zone lighting on drivers’ visual performance and glare perception has never been studied in a realistic setting. The goal of this study was to understand the impact of commercially available portable light towers (metal halide, LED, and balloon) and their orientation on drivers’ visual performance and their perceptions of glare. Participants drove through a realistic work zone simulated on the Virginia Smart Road. Visual performance was assessed by a detection task and perception of visibility and glare were assessed by questionnaires. Results indicated that the type of light tower and its orientation affect visual performance and perceptions of visibility and glare. Light towers aimed toward the driver resulted in lowering drivers’ visual performance, both objectively and subjectively. When the light towers were aimed away from or perpendicular to the driver, the visual performance was higher and the differences in visual performance between the types of light towers were minimal. These findings indicate that these orientations should be preferred for work zone light towers.
... As it was established, about 30% of pedestrians fail to observe the rules of crossing the road at designated places [5]. Despite increased efforts put in road infrastructure [4], still almost a quarter of all accidents occur on pedestrian crossings or around them. It follows from the presented research results that a decisive factor in the possibility of noticing a pedestrian are directional reflection coefficients of materials used for clothing worn by pedestrians. ...
Article
Full-text available
In Poland, throughout many years invariably numerous accidents occur with the participation of pedestrians. One of the reasons of such a state of affairs is incorrect lighting of conflict areas dedicated to pedestrian traffic. The article deals with the problem of lighting of pedestrian crossings. The present paper enumerates formal requirements concerning pedestrian crossing lighting from the point of view of the norms applicable in Poland to date. Analysis of the criteria assumed for the assessment of lighting shall be conducted. Investment into road infrastructure research can contribute to the safety improvement of unprotected participants of road traffic.
... Detection distance was defined as the distance at which the participant was able to detect the presence of the simulated worker in the work zone. Detection distance has been used as a measure of visual performance in nighttime roadway visibility research (1,(5)(6)(7)(8). ...
Article
Portable light towers are a significant source of glare to motorists entering a work zone. Although existing research has evaluated the effect of light tower orientation on visibility and glare, the effects of factors like mounting height, offset distance from the roadway, and number of light towers in the work zone, on visual performance and discomfort glare is not known. Understanding these relationships can help in developing illuminating guidelines for work zones that can reduce glare for drivers. The goal of this paper is to understand the effect of mounting height, offset distance to the roadway, and number of light towers in the work zone on drivers’ visual performance and discomfort glare. Participants drove through a realistic work zone and evaluated portable light towers in varying mounting heights, offset distances, and number of light towers in the work zone. Results showed that the mounting height and offset distances play a critical role in affecting the driver’s visual performance and discomfort glare rating. Portable light towers, irrespective of wattage and lumen output, at lower than a mounting height of 20 ft and closer to the roadway result in decreasing driver visual performance and increasing their discomfort glare. Portable light towers should be mounted at a height of at least 20 ft and balloon light towers with higher wattage (4,000 W and greater) and lumen output (400,000 lumens and greater) should be located at an offset distance of at least 10 ft from the roadway.
... These increases could be attributed to the increased amount of visual information that participants were able to extract from the area. The study's results are in agreement with those of existing research (Bhagavathula et al. 2018;Boyce and Bruno 1999;Edwards and Gibbons 2008;Gibbons et al. 2015;Janoff 1989;Minoshima et al. 2006) evaluating the effect of light level on visual performance and perceptions of visibility. There were differences in the light levels at which plateauing in visual performance was observed; these depended on location, age of the observer, light source type, and the observer. ...
Article
Light levels recommended for parking facilities should be backed by empirical research that accounts for all users. In the current study, pedestrians’ and drivers’ visual performance and their perceptions of safety, comfort, and visibility were evaluated at a parking garage and at parking lots with asphalt and concrete pavements under three light source types (high-pressure sodium luminaire, 3000 K light emitting diode [LED] luminaire, and 5000 K LED luminaire) and at multiple light levels. Visual performance involved facial and hand recognition, wheel stop detection, detection of a side-facing pedestrian, and detection of a vehicle backing up from a parking spot. Perceptions of safety, comfort, and visibility were assessed by means of a questionnaire. Results showed that in the parking garage, an increase in light level beyond 10 lux of average horizontal pavement illuminance did not result in a statistically significant increase in visual performance or perceptions of safety, comfort, and visibility. For parking lots of asphalt and concrete pavements, this plateauing was observed at the 2 lux light level. No statistical differences were observed between the light source types for the visual performance tasks, but the perceptions of safety, comfort, and visibility were highest for the 5000 K LED luminaires.
... These increases could be attributed to the increased amount of visual information that participants were able to extract from the area. The study's results are in agreement with those of existing research (Bhagavathula et al. 2018;Boyce and Bruno 1999;Edwards and Gibbons 2008;Gibbons et al. 2015;Janoff 1989;Minoshima et al. 2006) evaluating the effect of light level on visual performance and perceptions of visibility. There were differences in the light levels at which plateauing in visual performance was observed; these depended on location, age of the observer, light source type, and the observer. ...
Technical Report
The goal of this study was to understand the effects of lighting source types and light levels on the visual performance of pedestrians and drivers on the critical visual tasks in parking lots and garages. The results of this study will inform the lighting level recommendations for parking facilities in IES Recommended Practice (RP) documents. In the current study, pedestrians’ and drivers’ visual performance and their perceptions of safety, comfort, and visibility were evaluated at a parking garage and at parking lots with asphalt and concrete pavements under three light source types (high-pressure sodium luminaires, 3000-K light-emitting diode [LED] luminaires, and 5000-K LED luminaires) and at multiple light levels. Visual performance involved facial and hand recognition, wheel stop detection, detection of a side-facing pedestrian, and detection of a vehicle backing up from a parking spot. Perceptions of safety, comfort, and visibility were assessed by means of a questionnaire.
... Detection distance was defined as the distance at which the participant was able to detect the presence of the simulated worker in the work zone. Detection distance has been used as a measure of visual performance in nighttime roadway visibility research (1,(5)(6)(7)(8). ...
Conference Paper
Portable light towers are a significant source of glare to motorists entering a work zone. Although existing research has evaluated the effect of light tower orientation on visibility and glare, the effects of factors like (mounting height, offset distance from the roadway, and number of light towers in the work zone) on visual performance and discomfort glare is not known. Understanding these relationships can help in developing illuminating guidelines for work zones that can reduce glare for drivers. The goal of this paper is to understand the effect of mounting height, offset distance to the roadway, and number of light towers in the work zone on drivers’ visual performance and discomfort glare. Participants drove through a realistic work zone and evaluated portable light towers in varying mounting heights, offset distances, and number of light towers in the work zone. Results showed that the mounting height and offset distances play a critical role in affecting the driver’s visual performance and discomfort glare rating. Portable light towers, irrespective of wattage and lumen output, at lower than a mounting height of 20 ft. and closer to the roadway result in decreasing driver visual performance and increasing their discomfort glare. Portable light towers should be mounted at a height of at least 20 ft. and balloon light towers with higher wattage (4,000 W and greater) and lumen output (400,000 lumens and greater) should be located at an offset distance of at least 10 ft. from the roadway.
... Detection distance was defined as the distance at which the participant was able to detect the presence of the simulated worker in the work zone. Detection distance has been used as a measure of visual performance in previous nighttime roadway visibility research (Bhagavathula & Gibbons, 2013Edwards & Gibbons, 2008;Shinar, 1985;Zwahlen & Schnell, 1999). ...
Technical Report
Portable light towers are a significant source of glare to motorists entering a work zone. Although existing research has evaluated the effect of light tower orientation on visibility and glare, the effects of factors like mounting height, offset distance from the roadway, and number of light towers in the work zone on visual performance and discomfort glare are not known. Understanding these relationships can help to develop illumination guidelines for work zones that can reduce glare for drivers. The goal of this project was to understand the effect of mounting height, offset distance to the roadway, and number of light towers in the work zone on drivers’ visual performance and discomfort glare. Participants drove through a realistic work zone and evaluated portable light towers with varying mounting heights, offset distances, and number of light towers. Results showed that the mounting height and offset distances play a critical role in affecting the driver’s visual performance and discomfort glare rating. Portable light towers, irrespective of wattage and lumen output, at lower than a mounting height of 20 feet and closer to the roadway (in travel lanes than in the shoulder) result in decreasing drivers’ visual performance and increasing their discomfort glare. Portable light towers should be mounted at a height of at least 20 feet, and balloon light towers with higher wattage (4,000 watts and greater) and lumen output (400,000 lumens and greater) should be located at an offset distance of at least 10 feet from the roadway.
Article
Full-text available
A method for evaluating a driver's response in a nighttime crash scenario is offered. A pedestrian can be said to be within the headlight beam when the line representing the shape of a headlight beam equals the pedestrian approach vector. This method is based upon headlight beam mapping and the illumination necessary for drivers to recognize non-illuminated objects on an unlit road at night. The most notable information gained through this research is to be able to correlate headlight illumination with driver response distances. From 25 nighttime driver response distance experiments, information was gathered from many of the original authors. This information includes position left or right, headlight type, lighting, movement of the object or pedestrian, and the position (standing, slumped or laying). Also recorded were methodology variable such as experiment type, experiment type (closed course or road), whether the observer was driving and if the observer was asked to be certain of the target, or to respond as soon as possible. The headlight mapping and the experimental results allowed for the calculation of the beam size necessary before participants responded to pedestrians and objects of various shapes (black to white to retroreflective). Equations are given for various applicable beam patterns. The distance at which the headlight beam equation equals the pedestrian or object vehicle-fixed approach vector will be the distance at which the pedestrian or object entered the headlight beam. Secondary analyses are suggested as a means of addressing other variables that influence nighttime driver responses. The factors that influence a driver's ability to recognize an object at night and the limitations of these models will be addressed.
Article
According to machinery statistics of the Ministry of Economy, Trade and Industry, the quantity of electric lamps produced in Japan in 2010 was 797,000,000 (129.5% compared to the previous year). Of these, 70,000,000 were general lamps (95.5% compared to the previous year) and 35,000,000 were halogen lamps (109.7% compared to the previous year). The number of fluorescent lamps produced was 545,000,000 (86.9% compared to the previous year), and the number of general fluorescent lamps excluding backlights was 251,000,000 (104.5% compared to the previous year). Furthermore, the number of HID lamps produced was 9,700,000 (127.3% compared to the previous year). On the other hand, when looking at sales compared to the previous year, the results for general lighting electric lamps, halogen lamps, general fluorescent lamps, backlights, and HID lamps were 87.3%, 105.1%, 98.1%, 64.7%, and 110.7%, respectively. Moreover, the sales of bulb-type fluorescent lamps included in general fluorescent lamps were 83.9% when compared to the previous year. Adding up these numbers to discuss trends is not an easy task, but we can glean two conflicting factors from this data: a long-term reduction via transition to LED light sources, and a short-term recovery from the significant reduction caused by the economic downturn of 2009. Only backlights show a significant reduction of more than 30% for 2 years in succession, due in large part to a switch to LED lighting. Our main exhibitions included "LED Next Stage 2010" in March and "LED Japan 2010" in September, both in Japan, while overseas we held "Strategies in Light 2010" in February (Santa Clara USA), and Light + Building 2010 in April (Frankfurt Germany). For research activities, the "12th Symposium on the Science and Technology of Light Sources", and the "3rd Conference on White LEDs" were held jointly in July 2010 (Eindhoven, Netherlands), and abbreviated as "LS-WLED 2010". Changes continue to be made internationally as well in the illumination fields, from conventional tubes using discharge and heat radiation to solid LED light sources. The joint conference made it very clear that the future of these industries will have a strong influence on the direction of scholastic activities. As for incandescent bulbs, a report was made concerning tungsten material, but there was almost no sign of new products or research activities, with worldwide usage bans or stops in production. In Europe, ErP Directive (Energy-related Products Directive) exist to phase out sales, with 2012 set as a phase-out target domestically. A special issue of the Journal of the Illuminating Engineering Institute of Japan took a look back on the incandescent bulb's 130 year history. As for fluorescent lamps, there was no change in direction regarding their development for low energy, long-life sources of illumination, although there was a decrease in the number of new products announced. And although bulb-type fluorescent lamps offer the benefit of an initial low cost, bulb-type LED lamps are clearly dominating the market. New product development and research of LED light sources was very active. From a practicality standpoint, many new bulb-type LED lamp products are now on the domestic market, with luminous efficiency improvements, luminous flux improvements, reduction in weight, and diversification of E17 base products. Narrow light distribution angle was raised as an issue. Standardization activities were also held, and a JEL document was established for GX16t-5 straight tube LED lamps with base by the Japan Electric Lamp Manufacturers Association (JELMA). In the high-intensity discharge (HID) lamp field, product development and technological research related to ceramic metal halide lamps is as popular as ever. Unsaturated ceramic metal halide lamps and mercury free metal halide lamps were introduced at LS-WLED 2010. There were also many reports about other types of discharge lamps, including inductively-coupled or capacitively-coupled electrodeless lamps, microwave discharge lamps, and excimer discharge lamps. Furthermore, there were many reports with applied examples of nanotechnology as a new light source. With regard to lighting circuits, development of environment-conscious, low energy products is progressing, and there were many research reports on discharge control circuits, covering fluorescent lamps, HID lamps, and electrodeless lamps. There were also many reports on size reduction and light modulation for LED lighting circuits via improved circuit efficiency and simplified circuit structure.
Article
A promising approach to integrating lighting and vegetation, termed ecoluminance, along roadways for improving visual guidance and reducing energy use is proposed. The visibility of relevant objects along several simulated roadway applications (roundabouts, curved exit ramps, and urban boulevards) were compared when illuminated conventionally, and when designed with the ecoluminance approach. The ecoluminance approach had the largest estimated impact on drivers’ visibility when detecting pedestrians and other roadway hazards for roundabouts and for urban boulevards. The roundabout also had the greatest energy savings and as a result, had the greatest operating cost reduction.
Book
This book outlines the underlying principles on which modern road lighting is based, and provides the reader with knowledge of how these principles should be applied in practice. This book offers a completely fresh approach to the subject, reflecting how the technology of road lighting has progressed to keep up with the changes in lamp technology, especially in solid state light sources, and the increasing awareness of energy use and environmental issues. The book is divided into three parts. Part One describes lighting of open roads, with chapters discussing visual performance and comfort (including the effects of mesopic vision and age), and international standards and recommendations for road lighting. Lighting equipment is introduced; specifically lamps and luminaires in terms of their practical properties and features, but also the road surface and its characteristics. A chapter on Lighting Design makes the link between theory and practice, providing the reader with the knowledge needed for effective lighting design, including aspects relating to sustainability. The final chapter of Part One deals with lighting calculation conventions and measurements. Part Two is devoted to light pollution. The negative consequences of light pollution are described and tactics to restrict light pollution explained. Lighting criteria are defined that can be used by the lighting designer to guarantee installations stay within acceptable limits. International standards and recommendations on the restriction of light pollution are discussed. Part Three is devoted to tunnel lighting, with chapters discussing visual performance in tunnel environments, lighting criteria, standards and recommendations, and concluding with a chapter on tunnel lighting equipment and design. This book is a valuable resource for road lighting designers and engineers, students of lighting design and engineering, town planners, traffic engineers, environmental specialists, and lamp and luminaire developers and manufacturers.
Article
Intelligent lighting is responsible for providing an appropriate illuminance and balancing the environment and resources. An appropriate illuminance can improve visual effect of machine recognition, while it is always difficult to be measured and controlled. An illuminance measurement method by using depth measurement technology of binocular stereo vision is proposed in this study. Illuminance analysis models of single LED and combined LEDs are established, and theoretical calculation equations for analyzing the relationship between power, illuminance, and depth are proposed. The illuminance distribution of single LED and combined LEDs are measured. The difference between single LED and combined LEDs are obtained in terms of illuminance, power, energy efficiency, effective illuminance area, etc. The results show that the illuminance is proportional to power of LED consumed and inversely proportional to the square of depth of image. The higher the energy conversion efficiency under the high illuminance for both single LED and combined LEDs. The depth of image is measured by binocular stereo vision technology, which has a good measurement performance. The binocular stereo vision based illuminance measurement method proposed in this study is efficient, reliable and robust, which is in good agreement with the experimental results, and the relative error is less than 3.8 %. The illuminance measurement is realized without increasing the equipment and image acquisition workload, which lays the foundation for dynamic monitoring and controlling of illuminance. The research results can also be applied to related fields as well, such as the intelligent lighting of street lamp, high beam in automatic driving and supplement lamps in video monitoring.
Technical Report
Washington State Department of Transportation (WSDOT) evaluated continuous roadway lighting on mainline freeway segments in Washington State. An extensive literature review on the safety performance of roadway lighting was completed. As part of this research effort WSDOT developed multivariate random parameter (RP) models with specific lighting variables for continuous lighting on mainline freeway segments. Roadway lighting is often used as a countermeasure to address nighttime crashes and this research evaluates common assumption related to roadway lighting. The models developed for this research use crashes from the end of civil dusk twilight to the start of civil dawn twilight since lighting systems are of limited value outside these timeframes. Natural light conditions were estimated for crashes based on location and time of the crash event. Based on the RP results, the research team concludes that the contribution of continuous illumination to nighttime crash reduction is negligible. In addition to the findings on safety performance, a pilot LED project on US101 demonstrated that LED roadway lighting can significantly increase energy efficiency and environmental stewardship (e.g., reducing greenhouse gas emissions) while maintaining safety performance outcomes. The research team recommended modification to WSDOT design policy, including removal of the requirement of continuous mainline lighting and reduction of lighting where segment specific analysis indicates appropriate.
Chapter
A motorist’s visual performance can be assessed using a number of different performance criteria. The visibility of static objects (obstacles) and dynamic objects (other road users, including pedestrians) and the visibility of changes in the visual scene and the detection of relative movement are examples of important criteria. Detection just on the threshold of visibility is often not enough for safe driving: good supra-threshold visibility increases the chance of a motorist reacting in time. Another aspect, important for decreasing reaction time, is peripheral vision: noticing something out of the corner of the eye, “off” the line of sight, that needs attention. As will be explained in this chapter, peripheral vision is different in the mesopic vision range as compared to the photopic vision range. In order to be able to draw conclusions as to what lighting quality is needed under different situations, the individual relationships between photometric lighting parameters and the different performance criteria, such as revealing power, total revealing power, visibility level, small target visibility and relative visual performance, have to be studied. Fortunately, there are many research results on the relationships between the most important performance criteria and the various lighting parameters. These will be dealt with here. The impact of adverse weather conditions and of the effect of vehicle lighting on the visual quality obtained from fixed road lighting, are other items dealt with here. Finally, the neurological influence that lighting could possibly have in helping to keep the motorist alert will be discussed.
Thesis
Full-text available
Nighttime intersection crashes account for nearly half of all the intersection crashes, making them a major traffic safety concern. Although providing lighting at intersections has proven to be a successful countermeasure against these crashes, existing approaches to designing lighting at intersections are overly simplified. Current standards are based on recommending lighting levels, but do not account for the role of human vision or vehicle headlamps or the numerous pedestrian-vehicle conflict locations at intersections. For effective intersection lighting design, empirical evidence is required regarding the effects of lighting configuration (part of the intersection illuminated) and lighting levels on nighttime visibility. This research effort had three goals. The first was to identify an intersection lighting design that results in the best nighttime visibility. The second goal was to determine the effect of illuminance on visual performance at intersections. The third goal was to understand the relationships between object luminance, contrast, and visibility. To achieve these goals, three specific configurations were used, that illuminated the intersection approach (Approach), intersection box (Box), and both the intersection approach and box (Both). Each lighting configuration was evaluated under five levels of illumination. Visibility was assessed both objectively (visual performance) and subjectively (perceptions of visibility and glare). Illuminating the intersection box led to superior visual performance, higher perceived visibility, and lower perceived glare. For this same configuration, plateaus in visual performance and perceived visibility occurred between 8 and 12 lux illuminance levels. A photometric analysis revealed that the Box lighting configuration rendered targets in sufficient positive and negative contrasts to result in higher nighttime visibility. Negatively contrast targets aided visual performance, while for targets rendered in positive contrast visual performance was dependent on the magnitude of the contrast. The relationship between pedestrian contrast and perceived pedestrian visibility was more complex, as pedestrians were often rendered in multiple contrast polarities. These results indicate that Box illumination is an effective strategy to enhance nighttime visual performance and perceptions of visibility while reducing glare, and which may be an energy efficient solution as it requires fewer luminaires.
Article
Full-text available
Nighttime pedestrian visibility was studied under various combinations of driver expectancy (to see a pedestrian on the road), pedestrian clothing characteristics (dark clothing, light clothing, and dark clothing with retroreflective tags), and the detection criterion (pedestrian versus retroreflective tag). It was found that visibility distance increases with expectancy, but the magnitude of the effect varies as a function of whether or not the pedestrian is wearing the tag. Furthermore, it was shown that when the pedestrian is unexpected, the usefulness of the tag is significant only if the driver can rely on it as a criterion for detection (by prior knowledge of the association between the tag and the pedestrian). The difference in visibility when the tag is not associated with the pedestrian may explain the less-than-expected effectiveness of retroreflective materials on accident reduction.
Article
In the United States, pedestrian deaths account for nearly 20% of all traffic fatalities. During darkness the pedestrain's risk is increased. This risk is further increased if a pedestrian is wearing dark clothing or must travel on a roadway concurrently with a driver who has been drinking. In the laboratory phase of this study it was found that at low levels of illumination an individual's sensitivity to contrast decreases as his blood alcohol level increases. All subjects exhibited a significant (p<.01) decrease in contrast sensitivity at blood alcohol levels greater than 0.04%. In the road test phase of the study visibility distances were found to be unacceptably short for “dummy” pedestrians covered with black or gray fabric. Dummies covered with white fabric were safely visible for a driver traveling up to a speed of 50 M.P.H.: however, only reflectorized dummies were safely visible above that speed. At blood alcohol levels greater than 0.04% all of the observers exhibited a significant (p<.01) decrease in the mean visibility distance for each of the simulated pedestrian conditions.
AN EXPERIMENT WITH EIGHT MALE STUDENTS SHOWED THAT AT LOW LEVELS OF ILLUMINATION, AN INDIVIDUAL'S SENSITIVITY TO CONTRAST DECREASES AS HIS BLOOD ALCOHOL LEVEL INCREASES. ALL SUBJECTS EXHIBITED A SIGNIFICANT DECREASE IN CONTRAST SENSITIVITY AT BLOOD ALCOHOL LEVELS GREATER THAN 0.04 PERCENT. IN A ROAD TEST STUDY, VISIBILITY DISTANCES WERE FOUND TO BE UNACCEPTABLY SHORT FOR DUMMY PEDESTRIANS COVERED WITH BLACK OR GREY FABRIC. DUMMIES COVERED WITH WHITE FABRIC WERE SAFELY VISIBLE FOR A DRIVER TRAVELLING UP TO A SPEED OF 50 MPH. HOWEVER, ONLY REFLECTORIZED DUMMIES WERE SAFELY VISIBLE ABOVE THAT SPEED. AT BLOOD ALCOHOL LEVELS GREATER THAN 0.04 PERCENT ALL FOUR OBJECTS EXHIBITED A SIGNIFICANT DECREASE IN THE MEAN VISIBILITY DISTANCE FOR EACH OF THE SIMULATED PEDESTRIAN CONDITIONS.
Article
This study quantified drivers' ability to recognize pedestrians at night. Ten young and 10 older participants drove around a closed road circuit and responded when they first recognized a pedestrian. Four pedestrian clothing and two beam conditions were tested. Results demonstrate that driver age, clothing configuration, headlamp beam, and glare all significantly affect performance. Drivers recognized only 5% of pedestrians in the most challenging condition (low beams, black clothing, glare), whereas drivers recognized 100% of the pedestrians who wore retroreflective clothing configured to depict biological motion (no glare). In the absence of glare, mean recognition distances varied from 0.0 m (older drivers, low beam, black clothing) to 220 m (722 feet; younger drivers, high beam, retroreflective biomotion). These data provide new motivation to minimize interactions between vehicular and pedestrian traffic at night and suggest garment designs to maximize pedestrian conspicuity when these interactions are unavoidable.
Lighting for Exterior Environments: an IESNA Recommended Practice
IESNA Outdoor Environment Lighting Committee (RP 33). (1999). Lighting for Exterior Environments: an IESNA Recommended Practice. New York, Illuminating Engineering Society of North America: 47.