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Road markings visibility is usually assessed by means of the visibility level (VL). Several models have been developed to calculate the visibility distance on the road (Detect/PCDetect, Carve/Tarvip, Cost 331 and CIE 73). These models all approximate the visibility of a marking by estimating the diameter of an ‘equivalent’ disc. In this process, speculative hypotheses are made to calculate this diameter, labelled the equivalent area hypothesis, the equivalent perimeter hypothesis or the equivalent width hypothesis. To compare these hypotheses, a psychophysical experiment was conducted with eight participants and 120 stimuli. It was found that the merit of each hypothesis changed with the diameter of the equivalent disc. Above 0·1°, all the hypotheses gave good results, but the equivalent area hypothesis was found to be the best. Below 0·1°, the equivalent width hypothesis was more accurate, but further investigations are still needed.

Night driving is challenging for driving simulations. At night, the constraints on Computer Graphics performance are unusually strong, as many relevant details have low contrasts and low luminance values, while the overall contrast is very high, due to light sources from road lighting and vehicle headlamps. Some level of realism is needed in terms of contrast rendering, because contrast impacts visibility and motion perception, which in turn impact the driving behavior. This is usually achieved in Computer Graphics with Tone Mapping Operators (TMOs), in order to display the computed images on a standard, Low Dynamic Range (LDR) display device. We explore in this paper the drawbacks of these operators for nighttime driving simulations, focusing on motion cues, and discuss the potential benefit of the emerging technology of High Dynamic Range (HDR) display devices. We have focused on a night-time road environment with an incoming motorcycle. Two experiments have been conducted, with 33 participants. Time-to-Collision (TTC) was considered as a proxy for motion perception. TTC estimations were collected on a HDR display and compared to degraded visual environments. The first experiment shows that the visibility of the motorcycle’s outline is the main visual cue for the TTC estimation in nighttime conditions (but this doesn’t happen with cars). It suggests that the main drawbacks of TMOs with respect to TTC estimation involves the mapping of low contrasts, which either enhances or impairs the motorcycle visibility. The second experiment explores this hypothesis and shows that enhancing the visibility of the motorcycle leads to biases in the TTC estimation, whereas removing it does not impact the TTC estimation — at the cost of other realism problems. These results suggest that motion cues at night are more realistic with a HDR Display, and that such display devices may be useful in situations where a realistic perception of hardly visible contrasts is needed.

This paper aims to identify suitable and energy efficient luminous environments for two users sharing the same office and conducting various activities at the same time (paper and/or computer-based work, meeting with a visitor). The office is lit by daylight, controlled by an exterior shading system and by artificial light, composed of ceiling sources and a task lamp on each desk. 930 subjects participated in six psychophysical tests conducted on the internet, each dedicated to a user position and an activity. Multiobjective optimizations were then performed with the collected data in order to identify luminous environments that realized the best tradeoffs between visual conditions for both users and power demand. An optimized luminous environment, judged suitable, whatever the combinations of activities in the room, is proposed.; L'objectif de l'article est d'identifier des ambiances lumineuses adaptées mais aussi efficaces énergétiquement quand un bureau est occupé par deux usagers réalisant diverses activités simultanément (travail sur papier, ordinateur, réunion). Les données ont été collectées auprès de 930 participants qui ont réalisés une expérience sur internet. Une optimisation multicritère a ensuite été réalisée pour identifier les ambiances lumineuses réalisant les meilleurs compromis pour satisfaire les deux usagers du bureau tout en limitant la puissance consommée par l'éclairage artificiel.

Road delineation treatments enhance the ability of drivers to control their vehicle safely on winding roads. A simulator experiment compared night-time driving on a country road under three conditions: on an unlit road, on a road illuminated on curves by typical road luminaires, and on a road with an active lane delineation application, where self-luminous road studs are turned on to outline the lane and road edges as the driver approaches and passes the curves. The unlit condition induces greater lateral position variability and longer crossovers relative to the studs condition, demonstrating better lateral vehicle control in the latter. The luminaires condition induce greater lateral position variability in left curves, and longer crossovers in right curves, relative to the studs condition, which also demonstrates a better lateral vehicle control in the studs condition. At a subjective level, the participants perceived both the studs condition and the luminaires condition as safer, more comfortable and allowing better control than the unlit road. It was concluded that the tested application enhanced the ability of drivers to control the virtual car, as compared to an unlit road or road lighting.

Many models have been developed to predict the discomfort glare generated by one light source in the visual field. Some of them were generalized to predict discomfort glare from several sources, but they were not directly built from multi-source data. In their generalization, they do not consider the potential interactions due to the fact that the light sources are switched on together. In the present work, a psycho-visual experiment was conducted for a better understanding of the glare produced by several sources using a matching task at the Borderline between Comfort and Discomfort (BCD). A formula is proposed to compute the photometric and geometric characteristics of an equivalent source which generates the same level of discomfort glare as several sources switched on together. This formula is the first step towards a multisource model of discomfort glare. The practical implications are discussed.

Driving simulation could benefit from high dynamic range computer graphics images, as well as high dynamic range display devices. In this chapter, we review the potential benefits of this technology for various uses of driving simulators, and discuss the obstacles which make it difficult today to promote these technologies in driving simulation applications. Benefits are first expected in behavioral studies, where a close link between the simulated and the real visual experience improves the validity of the driving simulation experiments. This is the case, for instance, in night driving simulation, where very dark areas need to be displayed together with very bright ones.

Due to different visual tasks and gaze patterns, the discomfort glare experienced by pedestrians may differ from that experienced by drivers. This paper investigates the discomfort glare experienced by pedestrians under various urban LED luminaires through psychovisual experiments conducted on a test track. The ability of state-of-the-art models to predict the level of discomfort glare, measured on the de Boer rating scale, for this application is also investigated. With one exception, the models all overestimate the mean subjective discomfort glare compared to the experimental data. Models proposed by Lin et al (2015) and Bullough et al (2008, 2011) perform well. However, the implementation of these models is not straightforward because choices are needed to estimate some of the variables such as the background luminance and the glare source area.; Cet article s'intéresse à l'éblouissement d'inconfort des piétons sous différents éclairages urbains à LEDs. Une expérience psychovisuelle a été menée sur piste et des jugements de gêne sur l'échelle de De Boer ont été collectés auprès d'un panel d'une trentaine de sujets. La pertinence de différents modèles de la littérature a été testée en comparant les prédictions avec les données expérimentales. Les modèles de Lin et al. (2015) et Bullough et al. (2008,2011) paraissent être les plus adaptés pour ce type d'application. Cet article met aussi en lumière la difficulté de mise en oeuvre des modèles dans des scènes visuelles complexes.

Traffic management and road safety may benefit from self-powered LED road studs but to be effective they need to be visible to road users, without glare, whatever the environmental conditions. Some parameters, such as dry versus wet road surfaces, have not been investigated previously for LED installations. In this context, two experiments have been conducted to study the visibility and discomfort glare produced by a LED road stud. The results suggest tuning the luminous intensity of LED road studs according to the illumination and road surface conditions to ensure visual perception by road users while controlling energy consumption. A quantitative model is provided in order to link the dimming to the environmental parameters.