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A field experiment was performed to measure the effects of oncoming illuminance profiles with different photometric and temporal characteristics on visual recovery and subjective discomfort. Target detection time was correlated with the dosage, and rated discomfort was correlated with the peak illuminance of each profile. Older subjects generally had longer recovery times, but there were no differences between the age groups in terms of rated discomfort. The results suggest that discomfort glare is not predictive of visual disability and that control of luminous intensity at isolated points within the distribution of headlamps alone is not sufficient to minimize glare recovery.

Modern roundabout facilities are increasing in number throughout North America and the world. Appropriate vehicle lighting, including the application of intelligent headlighting systems, might help support safe, efficient driving behavior while navigating through these new intersection types. We present the results of a field study conducted to compare different vehicle lighting systems in terms of drivers' ability to detect and identify pedestrian activity, under different amounts of illumination from fixed outdoor lighting systems. The results are compared to analytical predictions of visibility using a validated visual performance model.

Vehicle headlamps are essential for driver safety at night, and technological evolution of headlamps over several decades has brought substantial improvements to driver visibility and comfort. Nonetheless, glare remains an important concern among many in the driving public, perhaps even more so in North America, where requirements for headlamps differ from those in much of the rest of the world. In most of the world, headlamps producing higher luminous flux are required to have automatic leveling and cleaning systems, thought to help reduce glare. The arrival of headlamp systems in the worldwide marketplace with luminous flux values just below those triggering requirements for leveling and cleaning systems will bring new questions about the causes of and countermeasures for glare.

The purpose of this paper is to quantitatively compare the efficiency, of silicon and silicon carbide power devices in power circuit environments. Models developed for the MOSFET, PiN rectifier, Schottky rectifier, for both silicon and silicon carbide will be presented. These models have been implemented in the SABER circuit simulator and used to simulate power circuits, in order to determine the efficiency of the silicon and silicon carbide devices. It is essential for a fair comparison that the two devices are optimally designed, hence optimization of area has been performed and an analytical expression, for the optimum area as a function of operating conditions, determined. The efficiency for the optimum silicon and silicon carbide devices as a function of frequency, blocking voltages and operating currents is then presented. It has been shown that the 5000V SiC MOSFET has efficiencies comparable to the 300V Si counterpart.

The present design standards for low beam headlamps offer significant flexibility regarding the distribution of light that they generate. Some headlamp systems produce significant amounts of foreground illumination, which increases the apparent brightness of the roadway surface close to the vehicle, and this increased brightness is seen as desirable by many individuals. Some individuals may prefer not only high but uniform foreground illumination. At almost any driving speed, however, any objects located in the visual foreground are too close to avoid with slowing or steering maneuvers. Further, published literature on the mechanisms for disability glare suggests that foreground illumination should have a negative impact in terms of the visibility of objects located well ahead in the visual field.

We summarize the development and initial deployment of a system that can be mounted along an intersection, curve, drive-in, or parking facility to efficiently gather relevant data about headlamp patterns that might relate to glare or visibility. The system can run autonomously to collect many vehicles per data collection period. The system includes a range finder to capture information when an approaching vehicle is at a specific location, a digital camera to store images of oncoming headlamp position (i.e., mounting height), two arrays of light sensors to measure the vertical headlamp illumination profile (e.g., angular position of headlamp beam cutoff or maximum luminous intensity), and a color-calibrated illuminance meter at the angular location of an oncoming driver's eyes. From the headlamp mounting height data and the vertical cutoff location data, an estimate of the headlamp aim distribution can be made.

In real world driving conditions, illumination from vehicle headlamps and, when present, from fixed roadway lighting combines to provide visibility for the driver. We present analyses of visibility along a representative roadway intersection scenario with median and market-weighted headlamp beam patterns including halogen and high intensity discharge headlamp beam patterns, and high beam headlamp beam patterns. Also investigated are interactions with the spatial extent of roadway lighting, either as part of a continuous lighting system or as a single roadway luminaire at the intersection junction, and the role of ambient illuminance from urban environments. The results of the analyses show the large influence of ambient illuminance from urban areas on the visibility of relevant targets, and show differential advantages of different headlamp beam patterns for different target locations where pedestrians might be encountered.

Craters in galvannealed coatings on steel sheet are depressions caused by non-uniform diffusive growth. Correlations have been sought between “crater” densities in galvannealed sheet steel and friction, powdering, and paint adherence, as relevant to the appearance, corrosion resistance and processing of auto body panels. Crater densities were established on a series of samplings from major producers, and related to frictional measurements from a binder-radius simulator, powdering levels from bend testing, and paint adherence assessments from a stone-chipping test. Results suggest that increased crater density decreases powdering, but does not aid in lubrication. In fact, decreased powdering could be correlated with increased friction levels. A strong correlation was found between increased crater density and increased paint adherence.

Photometric performance specifications for vehicle headlamp specifications in North America are given in terms of luminous intensity values at various angular locations with the objective of providing sufficient illumination for forward visibility while controlling for glare toward oncoming and preceding vehicle drivers. Abundant evidence suggests that luminous intensity is an appropriate metric for characterizing the degree to which a headlamp can produce disability glare through veiling luminances under a wide range of viewing conditions. Notwithstanding that discomfort glare exhibits a differential spectral sensitivity from the photopic luminous efficiency function used to characterize light, luminous intensity does not always predict discomfort glare. For example, the luminance of the luminous element(s) can be more predictive of discomfort when headlamps are viewed from relative close distances.

Present standards for vehicle forward lighting specify two headlamp beam patterns: a low beam when driving in the presence of other nearby vehicles, and a high beam when there is not a concern for producing glare to other drivers. Adaptive lighting technologies such as curve lighting systems with steerable headlamps may be related to increments in safety according to the Insurance Institute for Highway Safety, but isolating the effects of lighting is difficult. Recent analyses suggest that visibility improvements from adaptive curve lighting systems might reduce nighttime crashes along curves by 2%-3%. More advanced systems such as adaptive high-beam systems that reduce high-beam headlamp intensity toward oncoming drivers are not presently allowed in the U.S. The purpose of the present study is to analyze visual performance benefits and quantify potential safety benefits from adaptive high-beam headlamp systems.

Workers in construction and transportation sectors are at increased risk for work-related injuries and fatalities by nearby traffic. Barricade-mounted warning lights meeting current specifications do not always provide consistent and adequate visual guidance to drivers and can contribute to glare and reduced safety. Through an implementation of sensors and wireless communications, a novel, intelligent set of warning lights and a tablet-based interface were developed. The lights modulate between 100% and 10% of maximum intensity rather than between 100% and off in order to improve visual guidance and adjust their overall intensity based on ambient conditions. The lights can be synchronized or operated in sequential flash patterns at any frequency between 1 and 4 Hz, and sequential patterns automatically update based on global positioning satellite (GPS) locations displayed in the control interface.

Headlight glare is a major concern of the driving public. In the past couple of years there have been concerns expressed about the use of light emitting diode (LED) lighting technologies and possible impacts LEDs may have on people, including circadian disruption, retinal hazards, and glare. Under typical use cases, vehicle headlight exposures are insufficient to cause circadian disruption or retinal damage, but can result in disability and discomfort glare, as well as glare recovery. In general, white LEDs used for illumination have greater short-wavelength content than halogen lamps used in many headlights, and short wavelengths have been implicated in visual discomfort from bright lights at night. Previous literature is inconsistent regarding whether the spectral (color) content of a glare source affects the amount of recovery time needed to see objects, following exposure to a bright light such as a vehicle headlight.

Rear automotive lighting systems employing dynamic features such as sweeping or flashing are not commonly used on vehicles in North America, in part because they are not clearly addressed in vehicle lighting regulations. Nor is there abundant evidence suggesting they have a substantial role to play in driver safety. The results of a human factors investigation of the potential impacts of dynamic rear lighting systems on driver responses are summarized and discussed in the context of safety, visual effectiveness and the present regulatory context.

The advent of light-emitting diode (LED) technology for automotive lighting allows flexibility of the spectral distribution of forward headlighting systems, while meeting current requirements for “white” illumination. As vehicle headlights have become whiter (with more short-wavelength light output) over the past several decades, their potential impacts on visual discomfort for oncoming and preceding drivers have been hotly debated. It is known that a greater proportion of short-wavelength energy increases discomfort glare, and that increasing the background light level (e.g., through roadway lighting) will decrease perceptions of discomfort. More recently it has been demonstrated that the visual system exhibits enhanced short-wavelength sensitivity for perceptions of scene brightness.

Transportation safety agencies are working to consider how to best incorporate the potential safety benefits of intelligent vehicle lighting systems such as adaptive driving beam headlights and other systems on vehicles used by the general public. As these deliberations continue, additional data on the impacts of lighting technological developments are important to generate and share. An analytical study was performed to assess how different vehicle lighting configurations including ADB and other technologies can assist drivers in achieving visual acquisition of potential hazards along the road. The investigation also compared drivers varying in age and whose visual performance differs because of optical changes in the visual system. The importance of considering visibility for older drivers is critical because this group is an increasingly large proportion of the overall driving population.

Discomfort glare from vehicle lighting is more difficult to measure precisely than disability glare, but may have important implications for driver behavior, and in turn on driving safety. Many studies of discomfort glare have found that, as with disability glare, the illuminance at the eyes from a bright light is the primary determinant of the sensation of glare. Nonetheless, the luminance of a light source also can influence discomfort glare, especially when the source is close enough to subtend a relatively large visual angle on the order of a third of a degree or larger. In addition, interactions with the absolute illuminance from a light source are not well understood. The results of an experimental investigation of discomfort glare in terms of light source illuminance, luminance and size are presented and discussed along with implications for automotive lighting applications.

Vehicle forward lighting can use a multiplicity of light sources each varying in their spectral characteristics. Present standards for low beam headlight performance also allow variability in the peak intensities that drivers can be exposed to, as well as the durations of those exposures. Previous research has led to mixed results regarding whether the spectral distribution of a headlight source influences the length of time the visual system needs to recover the ability to see objects that might present hazards along the roadway. One recent study showed that the integrated light dose (intensity × duration) but not the spectral distribution impacted recovery times for targets presented in a constant, known location, where they would be viewed with the fovea. An experiment was carried out to assess whether the spectral distribution of a glare source might differentially impact one's ability to see a target using peripheral vision when the location of the target is not known.

Flashing emergency lights on police cars, fire trucks, and ambulances need to be bright enough to alert otherwise unaware drivers about their presence on and near the roadway. Anecdotal evidence suggests that public safety agencies select emergency lighting systems with red or blue flashing lights based on their apparent brightness, with brighter lights judged as "better." With the advent of light emitting diodes (LEDs), emergency flashing lights are brighter and produce more highly saturated colors, thereby causing greater discomfort and disability glare. As a result, first response workers are at higher risk for being injured or killed in vehicle crashes because approaching drivers cannot see them. In the present study, participants viewed red and blue flashing lights on a scale model police vehicle, conforming to present recommended practices for emergency lights. Lights varied in intensity and optical power (intensity × duration).

Recent naturalistic driving studies provide a useful means for gathering information about the potential role of lighting in driving safety. The Naturalistic Driving Study carried out through the Strategic Highway Research Program 2 (SHRP2) includes real-time driving data for crashes, near-crashes and baseline driving events for more than 3000 drivers across the United States. Among the data collected are oncoming illuminance recordings that can be used to estimate glare exposure for the drivers in the study. Data for crash events occurring at night were compared to those for baseline driving under similar conditions and by drivers of similar ages. The resulting light exposure data indicate that oncoming glare is likely to be only a very small factor associated with nighttime crashes, but that the influence of glare may increase for older drivers.

Nighttime driving cannot be accomplished without vehicle headlighting. A growing body of evidence demonstrates the role of lighting on visual performance and in turn on nightttime driving safety in terms of crashes. Indirect impacts of lighting via comfort or other factors are less well understood, however. A two-part field study using real-world drivers of an instrumented vehicle was conducted to assess the potential role of oncoming headlight glare as a factor in driving behaviors that might be related to increased crash risks. In the first part of the study, drivers' behaviors when navigating through roadway intersections having different levels of crash risk were recorded in order to identify responses that were correlated with the risk level. In the second part, drivers were exposed to different levels of glare from oncoming headlights; several of the same risk-related behaviors identified in the first part of the study were exhibited.