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This study aimed to investigate the impact of automotive headlights of different correlated colour temperatures (CCT) on the visual and non-visual performance of drivers. Forty drivers participated in the study, driving in a simulated night road for 45 min in three sessions. The LED headlights had CCTs of 3176 K, 4358 K and 6923 K, with an illuminance of 5 lx perpendicular to the participants' eyes. Heart rate variability (HRV), psychomotor vigilance task and Karolinska sleepiness scale were measured before and after driving. At the end of the trials, achromatic far and near visual acuity tests, as well as achromatic far and near contrast sensitivity tests, were conducted. The study revealed that CCT did not affect achromatic far and near visual acuity. However, CCT had an impact on achromatic near and far contrast sensitivity, with higher CCT resulting in improved achromatic contrast sensitivity. As the CCT decreased, participants exhibited increased reaction time, made more errors, and reported higher sleepiness. The most significant physiological changes in HRV, including alterations in low frequency (LF), high frequency (HF) and LF/HF, were observed at lower CCT. The findings of this study suggest that both the visual and non-visual performance of drivers were enhanced when high CCTs were used for automotive LED headlights. [ABSTRACT FROM AUTHOR]

Yellow glasses for nighttime driving are marketed as tools that can reduce headlight glare and improve visibility by cutting blue light. However, only few empirical evidences support these benefits. The present study was aimed to assess the effect of yellow lenses on reducing disability from peripheral glare caused by headlights and improving contrast sensitivity. On evaluating contrast sensitivity, the participants wore three types of lenses: clear (with 95% luminance transmission), gray (with 79% luminance transmission), and yellow (with 77% luminance transmission). The glare source was induced using low-beam headlights from oncoming vehicles positioned at a distance of 40 m. The results revealed that wearing gray and yellow lenses at night significantly reduced contrast sensitivity, while wearing yellow lenses under glare conditions slightly improved contrast sensitivity. Despite this slight improvement, the use of yellow lenses at night is not advisable, as the overall disadvantages surpass their benefits. These findings raise questions about the claimed benefits of yellow lenses for nighttime driving and highlight the need for further research to validate the effect of nighttime glasses. [ABSTRACT FROM AUTHOR]

The creation of heat is inextricably tied to the functioning of vehicle headlights, which presents a substantial problem for dependable and long-term operations. The concomitant rise in heat generation has grown to be a significant problem as the luminous effectiveness of light-emitting diode (LED) headlights continues to improve. Heat sinks have been commonly employed to remove surplus heat from the LED chips and other parts of the lighting system to solve this problem. This research investigates the impact of different heat sink fin architectures on the thermal performance of LED headlights by subjecting numerical models to varying LED powers ranging from 6 to 12 W across four fin models. Outcomes reveal that the diverse thermal characteristics resulting from variations in the number of fins in the heat sink lead to enhanced thermal dissipation of up to 73.6%. Furthermore, these heat sinks are subjected to vibrational testing under the ISO 16750 standard, assessing vibrational characteristics in three distinct scenarios: Passenger Car Engine, Passenger Car Sprung Masses, and Passenger Car Unsprung Masses. Through analysis, it reveals that the vibrational characteristics of the heat sinks align with established standards, reinforcing their reliability and suitability for automotive applications. [ABSTRACT FROM AUTHOR]

Thermoelectric generation (TEG)-based waste heat recovery technology is an example of a low-grade energy recovery application. This study proposes a waste heat recovery system that can store the recovered energy and run low-power automotive car lamps. Experimental analysis was conducted to examine the output characteristics of the TEG-based waste heat recovery system, focusing on how the structural components and operational parameters influenced these characteristics. The study also explored and optimized the working strategy of the system for driving light-emitting diode (LED) car lamps. Both the dynamic output characteristics of the system and the lighting attenuation rule of the lamps were evaluated. The results revealed that increasing the heating temperature would improve the recovered energy of the system. However, when a high-power LED chip was used for heat generation instead of an electrically controlled heating plate, a slightly larger amount of energy was collected at the expense of a slightly lower thermoelectric conversion rate. Furthermore, connecting a supercapacitor to the waste heat recovery system for energy storage increased the operational time of the lamps. The supercapacitor also served as a buffer for power and voltage fluctuations caused by variations in the heating temperature. These findings demonstrate that the waste heat recovery system not only meets the requirements of the LED car lamps but can also power other low-voltage and low-power devices. [ABSTRACT FROM AUTHOR]

The high photoluminescence quantum yield (PLQY) orange-red phosphor, which is of great significance for the application of phosphor-converted light-emitting diode (LED). Herein, the novel BaSrLu 4 O 8 :Eu2+ orange-red phosphor was synthesized, and the PLQY is enhanced from 30 % to 91 % by Al 2 O 3 assisted sintering. Combined with the trap energy level analysis, it is considered that the addition of Al 2 O 3 introduces new vacancies, which release electrons during high temperature sintering, creating a more favorable environment for the reduction of Eu3+, increasing the Eu2+ luminescence center in the matrix and improving the PLQY. The white LED device prepared with BaSrLu 4 O 8 :Eu2+ and Y 3 (Al,Ga) 5 O 12 :Ce3+ has a color rendering index of 84.4 at a low correlated color temperature of 4295 K. Meanwhile, the luminous brightness of the orange LED prepared by BaSrLu 4 O 8 :Eu2+ can maintain 89 % of the original light intensity in the simulated foggy day illumination experiment, which proves its excellent lighting prospect as an automobile steering lamp in foggy and smog extreme conditions. The results indicate that this work provides a new strategy for the reduction of Eu2+ while realizing the multi-application of phosphors. [Display omitted] [ABSTRACT FROM AUTHOR]

Energy-efficient road illumination systems are an indispensable part of any modern society to ensure safe nocturnal transportation of freight and passengers, assure better navigation, promote improved visibility of surroundings, and diminish the probability of occurrence of accidents and crimes. Simulative estimation of pertinent photometric parameters and probable energy expenditure before commissioning of projects is very desirable to project managers, transportation engineers, local authorities, and other stakeholders for envisaging a complete picture of the deliverables and ensuring total conformity with applicable lighting and energy codes. This simulation-based work was conducted with luminaire luminous intensity distribution data tables of different light-emitting diode luminaires having type II luminous intensity distribution patterns in the simulation environment of an industry-standard lighting simulation software. Thereafter, the multiple regression analysis technique was utilized upon the simulatively obtained substantial dataset to propound a model of twenty-four bivariate quadratic polynomial equations for estimating the changes in road surface illuminance parameters, and three general equations were derived with the same dataset, two for estimating road surface illuminance parameters and one for estimating energy efficiency. The propounded model and general equations can be readily followed by various stakeholders to rapidly estimate pertinent photometric parameters and installation energy efficiency and the approach expatiated in this work can prove to be useful for exploring inter-variable relationships, providing objective functions in optimization tools, and proffering neoteric, heuristic perspectives to lighting design. [ABSTRACT FROM AUTHOR]

This article is devoted to the positioning of glued parts by robots in the process of manufacturing automotive headlights, with the possibility of generalization to the mutual positioning of any 3D object. The authors focused on the description of the mathematical method that leads to the optimization of the robot arm setting and ensures the closest contact of the glued parts. The contact surfaces of the two joined parts are, in the ideal case, identical in shape and their optimal alignment is considered to best align the position of the nominal points on the base part with the position of the control (measured) points on the part manipulated by the robot. [ABSTRACT FROM AUTHOR]

• Riders moved significantly further away from overtaking vehicles equipped with Adaptive Headlamp Systems (AHS) compared to a control condition. • AHS has the potential to improve bicycling safety in nighttime conditions when lighting conditions are poor. Introduction : The risk of motor vehicle-bicyclist crashes and fatalities is greater during nighttime than daytime lighting conditions, even though there are fewer cyclists on roadways at night. Vehicle Adaptive Headlamp Systems (AHS) aim to increase the visibility of bicyclists for drivers by directing a spotlight to illuminate bicyclists on or near the roadway. AHS technology also serves to alert bicyclists to the approaching vehicle by illuminating the road beneath the rider and by projecting a warning icon on the roadway. Method: Here, we examined how bicyclists respond to different AHS designs using a large screen, immersive virtual environment. Participants bicycled along a virtual road during nighttime lighting conditions and were overtaken by vehicles with and without an AHS system. The experiment included five treatment conditions with five different AHS designs. In each design a box of white light was projected beneath the rider; in four of the designs an icon was also projected on the road that varied in color (white or red) and position (to the left of the rider at midline or to the left of the front wheel). Participants in the control condition experienced only non-AHS vehicles. Results: We found that riders in all AHS treatment conditions moved significantly farther away from overtaking vehicles with AHS systems, whereas riders in the control condition did not significantly move away from overtaking vehicles without AHS systems. Practical Applications: The experiment demonstrates that AHS has potential to increase bicycling safety by influencing riders to steer away from overtaking vehicles. [ABSTRACT FROM AUTHOR]

As urban greenery improves and the ecological environment is continuously optimized, road facilities are also impacted to varying degrees. For example, as vegetation grows, it causes varying degrees of obstruction to the lighting facilities on the roads. This article is based on vehicle-mounted LiDAR data and focuses on the point cloud data characteristics of different objects. Using appropriate modeling techniques, it accurately models road surfaces, green belts, streetlights, and other objects. On the Lumion platform, this system creates a 3D visualization of road scenes and examines the interplay between objects and lighting space, analyzing lit areas. Leveraging the precise 3D spatial relationships found in point clouds, it determines the effective illumination area on the ground from streetlights after object obstruction, comparing it to the theoretical illumination area. This not only visualizes the road scene but also quantifies the lighting obstruction rate. Furthermore, it assesses the lighting conditions in road scenes based on illuminance distribution, offering scientific insights and suggestions for enhancing road lighting. [ABSTRACT FROM AUTHOR]

This preliminary study presents the development of integrating a real-time mobile device with a machine vision algorithm to assess the retroreflectivity of the broken lane lines of in-service road marking. A stereo camera was used as the photometer, and the measuring vehicle's headlights were used as the illumination system. The machine vision algorithm includes marking centroid determination, standard measuring condition control, illumination condition calculation, and luminance measurement. The test results show that the average absolute error percentage of 47 marking samples is 6.1%, with the highest and lowest accuracies of 99.9% and 85.7%, respectively. The left and right lane line (broken line) markings can be evaluated simultaneously in a single pass up to 100 kph. The hardware package, including a stereo camera, a camera support beam, cables, and a laptop computer, costs approximately USD 3,500, which is much lower than the cost of conventional and advanced fully automatic retroreflectometers. Moreover, the developed method is for general usage and can be easily modified and applied to camera sets and vehicle carriers of different specifications. Although the results are promising, the proposed method has some limitations. First, the accuracy decreases when the test section is rough with bumps and dips. Second, this algorithm is not ready for surveying solid lines. Furthermore, the current version can only be implemented under vehicle headlights. Future work can focus on improving the hardware and machine vision algorithm to overcome the challenges. This preliminary study aims to develop an integrated system for automatically surveying road markings' retroreflectivity. In many countries and regions, road markings' retroreflectivity is only examined during construction instead of being inspected periodically due to a lack of efficient equipment, budget, and techniques for surveying. Although some commercial instruments have shown promising results, no detailed information or discussion on the algorithm of reflective light acquisition and retroreflectivity computation has been reported. This study presents a detailed description about the developed machine vision algorithm that can detect and analyze the marking's dry retroreflectivity in the nighttime. The hardware package, including a stereo camera, a camera support beam, cables, and a laptop computer, costs approximately USD 3,500, which is lower than the cost of conventional and advanced fully automatic retroreflectometers. Moreover, the developed method is for general usage and can be easily modified and applied to camera sets and vehicle carriers of different specifications. However, currently the algorithm is only for broken lane line under relatively dark environmental condition. Future studies are suggested to include more road marking types and reduce the effects of ambient light sources on the analyzed results. [ABSTRACT FROM AUTHOR]

In order to find optimized headlight distributions based on real traffic data, a three-step approach has been chosen. Since the complete investigations are too extensive to fit into one single publication, this paper is the second of three papers. Over the course of these papers, a novel way to optimize automotive light distributions based on real-life traffic and eye-tracking data is presented. Over all three papers, 119 test subjects participated in the studies, with over 15,000 km of driving, including recordings of gaze behavior, light data, detection distances and other objects in traffic. In the first paper, an ideal headlight distribution for straight roads with no other road users was identified. The second paper aims to collect the data required to modify this idealized headlight distribution for use on real roads. The first step is to find the extent to which real roads differ from an ideal, straight road. To do this, the German traffic space was analyzed. A new test vehicle recorded video and GPS data over a selected route. The video data were then evaluated by a machine learning algorithm. Object recognition software was used to find different traffic participants and road signs. Camera calibrations were used to find the exact angles of these objects. Using publicly available road data combined with the recorded GPS data, the video data were split into different road categories, and traffic object distributions were calculated for urban roads, country roads and motorways. The resulting analyses provided representative distributions of vehicles and highway signs along different types of roadways and roadway geometries. The GPS data were also used to find the curvature distributions along the selected route. These data were then used to optimize segment sizes for an adaptive driving beam. Overall, increasing the number of segments above 100 did not have appreciable benefits. These data will also be used in the third paper, where along the same route, the gaze distribution of drivers was recorded and analyzed. [ABSTRACT FROM AUTHOR]

In order to find optimized headlight distributions based on real traffic data, a three-step approach has been chosen. The complete investigations are too extensive to fit into a single paper; this paper is the last of a three part series. Over the three papers, a novel way to optimize automotive headlight distributions based on real-life traffic and eye tracking data is presented. Across all three papers, a total of 119 test subjects participated in the studies with over 15,000 km of driving, including recordings of gaze behaviour, light data, detection distances, and other objects in traffic. In this third paper, driver gaze behaviour is recorded while driving a 128 km round course, covering urban roads, country roads, and motorways. This gaze behaviour is then analysed and compared to prior work covering driver gaze behaviour. Comparing the gaze distributions with roadway object distributions from part two of this series, Analysis of Real-World Traffic Data in Germany and combining them with the idealized baseline headlight distribution from part one, different optimized headlight distributions can be generated. These headlight distributions can be optimized for different driving requirements based on the data that is used and weighting the different road types differently. The resulting headlight distribution is then compared to a standard light distribution in terms of the required luminous flux, angular distribution, and overall shape. Nonetheless, it is the overall approach that has been taken that we see as the primary novel outcome of this investigation, even more than the actual distribution resulting from this effort. [ABSTRACT FROM AUTHOR]

In order to find optimized headlight distributions based on real traffic data, a three-step approach is chosen. Since the complete investigations are too extensive to fit into a single publication, this paper is the first in a series of three publications. Over three papers, a novel way to optimize automotive headlight distributions based on real-life traffic and eye-tracking data is presented, based on 119 test subjects who participated in over 15,000 km of driving, including recordings of gaze behavior, light data, detection distances, and other objects in traffic. In the present paper, a baseline headlight distribution is derived from a series of detection tests conducted under ideal conditions, with a total of three tests, each with 19–30 subjects, conducted within the same test environment. In the first test, the influence of low beam intensity on the detection of pedestrians on the sidewalk ( 5.0   m from the center of the driving lane) is investigated. In the second test, the influence of different high beam intensities was investigated for the same detection task. In the third test, the headlight distribution and intensity are kept constant at a representative high beam level, but the detection task is changed. In this test, the pedestrian detection target is placed along different detection angles, ranging from immediately adjacent to the road ( 2.5 ° ) to 15.5   m away from the center of the driving lane ( 8.0 ° ). As mentioned, all of these tests were conducted under ideal conditions, with the studies taking place on an airfield with a 1.2  km long straight road and normal road markings, but without oncoming traffic, tasks other than keeping the vehicle with cruise control within its lane, or other distracting objects present. The tests yielded two sets of data; the first is the intensity, based on the first two studies, needed to ensure sufficient intensity to detect objects under ideal conditions at distances needed for different driving speeds. The last test then uses these intensities and necessary variations in the required intensity to create an idealized, symmetric headlight distribution as a baseline for subsequent publications. Although the distribution applies only to passenger vehicles like the one used in the test, the same approach could be applied to other vehicle types. The second paper of this series will focus on real traffic objects and their distributions within the traffic space in order to identify relevant areas in headlight distribution when driving under real traffic conditions. The third paper of this series will analyze driver gaze distributions during real driving scenarios. The data from all three papers are used to create optimized headlight distributions, thereby showing how such an optimized distribution relates to current headlight distributions in terms of luminous flux, intensity, and overall distribution. [ABSTRACT FROM AUTHOR]

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Additive manufacturing (AM) processes present unique opportunities for the repair of high-value-added industrial and consumer plastic products, which otherwise are destined for the landfill at the end of their life and contribute to the growing environmental and health issues. In this work, we propose a novel method of integrating fused filament-based additive fabrication with the hot staking method to repair a complex automotive component, namely headlight. Newly formulated polypropylene-based composite filaments were used to 3D print a set of staking posts and the missing brackets in the damaged headlight to enable their effective reuse of the repaired assembly. Three staking designs were tested in the first phase of the experiments with the respective geometrical configurations, viz. knurled, domed, and hollow. Strength tests were conducted to rank the performance of the joints against the highest ultimate shear strength values, toughness, and repeatability. The joint design with a domed-shaped profile ranked the best across these criteria. In the second phase of the study, the main printing parameters, including printing temperature, nozzle head penetration in the substrate, printing speed, and layer height, were optimised to increase the joint strength. Based on the design of experiment, the dome-shaped stakes, which were printed using a nozzle temperature of 240 ∘ C , tip penetration of 0.3 mm, 3D printing speed of 12 mm/s, and a layer height of 0.15 mm demonstrated the highest mechanical performance with the bond strength of 7.27 MPa. The repaired headlight was tested under cycling loading showing excellent durability without noticeable degradation of the staked joints upon 10,000 cycles. [ABSTRACT FROM AUTHOR]

DC-biased optical orthogonal frequency division multiplexing (DCO-OFDM) has been introduced to visible light networking framework for connected vehicles (LiNEV) systems as a modulation and multiplexing scheme. This is to overcome the light-emitting diode (LED) bandwidth limitation, as well as to reduce the inter-symbol interference caused by the multipath road fading. Due to the implementation of the inverse fast Fourier transform, DC-OFDM suffers from its large peak-to-average power ratio (PAPR), which degrades the performance in LiNEV systems, as the LEDs used in the vehicles' headlights have a limited optical power-current linear range. To tackle this issue, discrete Fourier transform spread-optical pulse amplitude modulation (DFTS-OPAM) has been proposed as an alternative modulation scheme for LiNEV systems instead of DCO-OFDM. In this paper, we investigate the system performance of both schemes considering the light-emitting diode linear dynamic range and LED 3 dB modulation bandwidth limitations. The simulation results indicate that DCO-OFDM has a 9 dB higher PAPR value compared with DFTS-OPAM. Additionally, it is demonstrated that DCO-OFDM requires an LED with a linear range that is twice the one required by DFTS-OPAM for the same high quadrature amplitude modulation (QAM) order. Furthermore, the findings illustrate that when the signal bandwidth of both schemes significantly exceeds the LED modulation bandwidth, DCO-OFDM outperforms DFTS-OPAM, as it requires a lower signal-to-noise ratio at a high QAM order. [ABSTRACT FROM AUTHOR]

The design of exterior lighting is crucial for automotive manufacturers to ensure the visibility and safety of the driver. This article proposes a new strategy to control and diagnose one or more exterior lighting functions in electric vehicles by maximising the electrical faults that are detected and their transfer over a single-wire. The outcome is a decreased system cost and an additional method for vehicle lighting infrastructure control and diagnosis. Virtual simulation tools are used to explore the correlation between master-slave architecture and the effectiveness of the single-wire approach to comply with safety and regulatory demands. Safety-related and non-safety-related needs are explored to properly assess lighting functions, internal logic, and fault-case scenarios. Furthermore, assessing the viability of minimizing wire harness utilization while retaining the diagnostic capabilities for the controlled lighting sources, thereby simultaneously reducing the vehicle's overall weight. This approach aims to concurrently decrease the overall weight of the vehicle. This work has three main contributions: (1) the development of efficient and reliable lighting systems in electric vehicles, a critical factor for achieving optimal performance, ensuring customer satisfaction, meeting regulatory compliance, and enhancing cost-effectiveness in automotive lighting systems. (2) Framework for future development and implementation of lighting systems in electric vehicles. (3) Simulation of the hardware architecture associated with the system strategy to achieve the desired system strategy for effectively applying the single-wire approach. [ABSTRACT FROM AUTHOR]

Background: High-quality surgical lighting is often lacking in low-resource settings. Commercial surgical headlights are unavailable due to high cost and supply and maintenance challenges. We aimed to understand user needs of a surgical headlight for low-resource settings by evaluating a preselected robust but relatively inexpensive headlight and lighting conditions. Methods: We observed headlight use by ten surgeons in Ethiopia and six in Liberia. All surgeons completed surveys about their lighting environment and experience using headlight, and were subsequently interviewed. Twelve surgeons completed logbooks on headlight use. We distributed headlights to 48 additional surgeons, and all surgeons were surveyed for feedback. Results: In Ethiopia, five surgeons ranked operating room light quality as poor or very poor; seven delayed or cancelled operations within the last year and five described intraoperative complications due to poor lighting. In Liberia, lighting was rated as "good", however fieldnotes, and interviews noted generator fuel-rationing, and poor lighting conditions. In both countries, the headlight was considered extremely useful. Surgeons recommended nine improvements, including comfort, durability, affordability and availability of multiple rechargeable batteries. Thematic analysis identified factors influencing headlight use, specifications and feedback, and infrastructure challenges. Conclusion: Lighting in surveyed operating rooms was poor. Although conditions and need for the headlights differed between Ethiopia and Liberia, headlights were considered highly useful. However, discomfort was a major limiting factor for ongoing use, and the hardest to objectively characterise for specification and engineering purposes. Specific needs for surgical headlights include comfort and durability. Refinement of a fit-for-purpose surgical headlight is ongoing. [ABSTRACT FROM AUTHOR]

This study developed and implemented a driving power supply for light-emitting diode (LED) array streetlamps. The power stage was a quasi-resonant (QR)-flyback converter, its input power was the alternating-current power, and the LED array streetlamp was driven by the direct-current output power. The developed QR-flyback converter was operated in discontinuous conduction mode, and the pulse-width modulation (PWM) control chip was used to switch and conduct at the resonant valley of the drain-source voltage on the metal-oxide-semiconductor field-effect transistor (MOSFET) switch to reduce the switching loss. Moreover, the PWM control chip had a disable function, which was connected with a bright and extinguishable control circuit, and the high/low voltage level signal output by the Arduino development board can be used to control the output power of the QR-flyback converter, achieving bright and extinguishable controls for the LED array streetlamp. [ABSTRACT FROM AUTHOR]

Electrically driven polar-plane-free faceted InGaN light-emitting diodes (LEDs) are demonstrated on semipolar ( 1 ¯ 1 ¯ 2 2 ¯ ) GaN substrates. The doping properties on the ( 1 ¯ 1 ¯ 2 2 ¯ ) plane are investigated using planar LED structures. After establishing the doping conditions, three-dimensional faceted LED structures composed of semipolar and nonpolar planes are fabricated by regrowth on the ( 1 ¯ 1 ¯ 2 2 ¯ ) GaN substrates with dielectric masks. The fabricated LEDs exhibit a clear rectifying property and a polychromatic emission derived from facet-dependent emission colors, which can be tuned by altering the mask geometry. These observations suggest that polar-plane-free LED structures may lead to highly radiative polychromatic light emitters. [ABSTRACT FROM AUTHOR]

This tutorial paper focuses on the physical origin of thermal droop, i.e., the decrease in the luminescence of light-emitting diodes (LEDs) induced by increasing temperature. III-nitride-based LEDs are becoming a pervasive technology, covering several fields from lighting to displays, from automotive to portable electronics, and from horticulture to sensing. In all these environments, high efficiency is a fundamental requirement, for reducing power consumption and system cost. Over the last decade, a great deal of effort has been put in the analysis of the efficiency droop, the decrease in LED internal quantum efficiency (IQE) induced by high current density. On the other hand, an IQE decrease is observed also for increasing temperature, a phenomenon usually referred to as thermal droop. For commercial LEDs, the IQE decrease related to thermal droop can be comparable to that of efficiency droop: for this reason, understanding thermal droop is a fundamental step for making LEDs capable of operating at high temperature levels. In several fields (including street lighting, automotive, photochemical treatments, projection, entertainment lighting, etc.), compact and high-flux light sources are required: typically, to reduce the size, weight, and cost of the systems, LEDs are mounted in compact arrays, and heat sinks are reduced to a minimum. As a consequence, LEDs can easily reach junction temperatures above 85–100 °C and are rated for junction temperatures up to 150–175 °C (figures from commercially available LED datasheets: Cree XHP70, Osram LUW HWQP, Nichia NVSL219CT, Samsung LH351B, and LedEngin LZP-00CW0R) and this motivates a careful analysis of thermal droop. This paper discusses the possible physical causes of thermal droop. After an introduction on the loss mechanisms in junctions, we will individually focus on the following processes: (i) Shockley–Read–Hall (SRH) recombination and properties of the related defects; (ii) Auger recombination and its temperature dependence, including the discussion of trap-assisted Auger recombination; (iii) impact of carrier transport on the thermal droop, including a discussion on carrier delocalization, escape, and freeze out; (iv) non-SRH defect-related droop mechanisms. In addition, (v) we discuss the processes that contribute to light emission at extremely low current levels and (vi) the thermal droop in deep ultraviolet LEDs, also with reference to the main parasitic emission bands. The results presented within this paper give a tutorial perspective on thermal droop; in addition, they suggest a pathway for the mitigation of this process and for the development of LEDs with stable optical output over a broad temperature range. [ABSTRACT FROM AUTHOR]

Photoluminescent paints for road marking application have been evaluated through laboratory measurements and visibility computations. The luminance decay in the dark was measured after constant excitation during at least 6 hours. To study the effect of night-time lighting conditions, luminance was measured under a constant low illumination (simulating moon and light pollution), and a periodic lighting, simulating automotive traffic. Measurements were also carried out on luminescent road marking applied on real pavement in a full-scale mock-up. Then, possible uses and limits of photoluminescent road markings were investigated through visibility computations based on the COST 331 model. Findings suggest luminescent road markings could strengthen the visual guidance of drivers on the road with traffic by increasing the visibility distance beyond the headlamp beams during the first few hours of the night, and in unlit areas such as bicycle paths, but the performance depends on the night-time illumination level. [ABSTRACT FROM AUTHOR]

• Crash outcomes related to six vehicle technologies were calculated for drivers 35–54 and 70 +. • Older drivers may benefit most from intersection assistance features. • Technologies can reduce crashes, injuries, and fatalities for drivers of all ages. Introduction : Age-related changes and frailty are among the reasons that older drivers are overrepresented in certain crash types. Vehicle safety features that address these crash types may therefore deliver greater safety benefits for older drivers than for other age groups even though they are designed for the general population. Methods: U.S. crash data from 2016–2019 were used to estimate the proportion of crash involvements and fatal and nonfatal driver injuries for older (70 years old and above) and middle-aged (35–54 years old) drivers from crash scenarios to which current crash avoidance features, improved headlights, and forthcoming vehicle-to-vehicle (V2V)-connected intersection-assistance features could be relevant. Risk ratios were then calculated to determine the relative benefits of each technology for older drivers compared with middle-aged drivers. Results: Combined, these technologies were potentially relevant to 65 % of older driver and 72 % of middle-aged driver fatalities during the study period. Intersection assistance features showed the most promise for older drivers. Such features were potentially relevant to 32 % of older driver crash involvements, 38 % of older driver injuries, and 31 % of older driver fatalities. Intersection assistance features were significantly more likely to be relevant to older driver deaths than middle-aged driver fatalities (RR, 3.52; 95 % CI, 3.33–3.71). Conclusions: Vehicle technologies have the potential to substantially reduce or mitigate crashes and the injuries that they cause for everyone, but the potential safety impact of each technology varies by driver age because different age groups are over- or underrepresented in specific crash scenarios. Practical applications: With the older driver population growing, these findings underscore the need to bring intersection assistance technologies to the consumer market. At the same time, everyone stands to benefit from currently available crash avoidance features and improved headlights, so their use should be promoted among all drivers. [ABSTRACT FROM AUTHOR]

In the past, polarizing filters were attached to cars' halogen headlights to reduce glare for other vehicles. However, the filters absorbed a significant amount of light and made it difficult for drivers to see properly. Coupled with overheating issues and numerous technical and logistical limitations, polarized automotive lighting systems have not become widespread. In this research, we propose using a polarized LED lighting system to improve drivers' visibility. Our results demonstrated an illuminance reduction of up to 97.5% when simultaneously using a polarized headlight filter and flip plate. Additionally, our system's lower operating temperatures resulted in a lifespan increase of approximately 120 times compared to a conventional halogen lighting system. [ABSTRACT FROM AUTHOR]