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To ensure adequate visibility without excessive glare, vehicle headlights are designed to use a specific source of illumination. The optical designs of headlights gather the luminous flux produced by the light source to produce a useful beam pattern that meets the relevant requirements and standards for vehicle forward lighting. With the advent of solid state, light emitting diode sources for general illumination, an increasing number of LED replacement headlight bulb products has emerged over the past decade. In most cases, these LED replacement bulbs are not permitted for legal use on public roadways, but some countries have begun to permit specific LED replacement bulbs to be used legally on the road for specific makes, models and production years of certain vehicles. If they can be demonstrated to produce a beam pattern that meets the photometric requirements for a legal headlight, they are permitted to be used legally for on-road use.

As new headlight technologies begin to take hold in vehicular forward lighting systems and they become more commonplace on vehicles, new frameworks for evaluating the performance of these systems are being developed and promulgated. The objective of each of these systems is the same, namely, improving safety by ensuring that vehicle lighting provides sufficient visibility for drivers without negative impacts such as glare. Recent research has shown the direct link between improved driver visibility and reduced nighttime crashes. To the extent that headlight evaluation systems can be compared using visual performance modeling approaches, it should be possible to relate improved visibility from high-performing headlight systems to the potential for reduced nighttime crashes. In the present paper we demonstrate how visual performance modeling in conjunction with vehicle headlight evaluations can lead to predictions of improved safety and ultimately, beneficial economic impacts to society.

Flashing lights on emergency and maintenance vehicles should be critical components to alerting, informing and managing drivers as they navigate around work zones, vehicle accidents and other roadway emergency incident scenes. These vehicles often also use distinctive colors and markings to identify the type of vehicle and potentially provide drivers with information about the nature of the incident they are approaching. In order to begin to understand how these elements (flashing lights and vehicle/marking colors) contribute to perception, a study was carried out in which participants viewed pairs of roadway scenes using scale model vehicles and lights adjusted to produce similar apparent intensities as full-scale lighting systems. In some cases the colors of the flashing lights were coordinated with those of the vehicle and its reflective markings, and in other cases the colors were not coordinated.

Flashing emergency and warning lights are critical elements of public safety and traffic control during roadway incidents. These lights should not only alert drivers to their presence, but also should inform them of who and what is present on the scene, and should help to manage the responses of drivers as they navigate past the incident. First responder and driver safety depend upon all three of these functions, yet standards focus almost entirely on alerting drivers. A full-scale outdoor field study was carried out during daytime, during nighttime on dry pavement and during nighttime on wet pavement, using a mock-up roadside scene containing three police vehicles. The lights on the vehicles were adjusted to produce different levels of intensity, flash rate, and synchronization of lights across all three vehicles. In some cases, sequentially flashing lights were present.

The current development of automotive lighting strives towards more and more lighting installations on vehicles. Additionally, to that, manufacturers start animating these lighting installations as coming home or leaving home greetings from the car to the driver. In a previous paper we have shown, that these additional animations are in fact not distracting to other road users and when used correctly, e.g. in a sequential turn indicator, can be beneficial to the overall traffic safety. This study then aims to investigate the potential influence of illuminated logos on road safety. European lawmakers forbid the use of illuminated advertisements on vehicles to minimize the danger of distraction for other road users and thereby negatively influencing traffic safety. As of now, active illumination of the manufacturer’s logo is considered an advertisement.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

Recent technological developments have begun to add a number of new configurations for vehicle forward lighting to the realm of possibility, including high-intensity discharge and light-emitting diode headlamps, and adaptive forward-lighting systems. These systems can offer substantial differences in performance and appearance from conventional filament-based headlamps that have been ubiquitous for many decades. These differences have not gone unnoticed by the U.S. driving public. A review of newspaper articles published during the past several years was conducted in order to assess public perceptions of vehicle headlamps in terms of their ability to support visibility and their impacts on headlamp glare.

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.

Rear signal lighting on vehicles has two primary functions: informing other drivers about the presence of a vehicle on the roadway, and alerting those other drivers to intentions of a vehicle's driver before actions such as turning or stopping occur. In the present paper, reports, articles and other technical literature, pertaining to rear lighting signal system photometric requirements and use of dynamic display features, are reviewed. The objective is to synthesize recommendations for configuring rear lighting in order to optimize systems for different ambient weather and lighting conditions, dirt accumulation, and warning functions. Research results from European, North American and Japanese contexts are discussed.