The Experts below are selected from a list of 4632 Experts worldwide ranked by ideXlab platform
Madhuri Gogula - One of the best experts on this subject based on the ideXlab platform.
-
Assessment of Sag Curve Design Criteria considering Modern Headlamp Performance
Transportation Research Record: Journal of the Transportation Research Board, 2008Co-Authors: H. Gene Hawkins, Madhuri GogulaAbstract:For more than 50 years, headlight sight distance has been one method for calculating the length of sag vertical curves; the others are passenger comfort, drainage control, and general appearance. The headlight sight distance is based on a 1° upward divergence of the Headlamp beam. Over the past 20 years, Headlamps have transitioned from being 100% sealed beam to modern replaceable bulb Headlamps that project less light above the horizontal plane than the sealed-beam Headlamps that are the basis for sag curve design. This paper describes theoretical and field measurements of the illuminance levels provided by sealed-beam and modern Headlamps. The results of the analysis indicate that modern Headlamps provide significantly less light above the horizontal than sealed-beam Headlamps, indicating a potential need to modify the design equations for sag vertical curves. According to the theoretical analysis, the upward divergent Headlamp angle used in the sag curve design equation should be reduced from 1° to between 0.75° and 0.90°. The field analysis indicated a significant difference in illuminance levels from the theoretical analysis, but the results also indicate a need to reduce the Headlamp angle used in sag curve design.
-
Assessment of Sag Curve Design Criteria Considering Modern Headlamp Performance
Transportation Research Record, 2008Co-Authors: H Gene Hawkins, Madhuri GogulaAbstract:For more than 50 years, headlight sight distance has been one method for calculating the length of sag vertical curves; the others are passenger comfort, drainage control, and general appearance. The headlight sight distance is based on a 1° upward divergence of the Headlamp beam. Over the past 20 years, Headlamps have transitioned from being 100% sealed beam to modern replaceable bulb Headlamps that project less light above the horizontal plane than the sealed-beam Headlamps that are the basis for sag curve design. This paper describes theoretical and field measurements of the illuminance levels provided by sealed-beam and modern Headlamps. The results of the analysis indicate that modern Headlamps provide significantly less light above the horizontal than sealed-beam Headlamps, indicating a potential need to modify the design equations for sag vertical curves. According to the theoretical analysis, the upward divergent Headlamp angle used in the sag curve design equation should be reduced from 1° to bet...
H Gene Hawkins - One of the best experts on this subject based on the ideXlab platform.
-
Assessment of Sag Curve Design Criteria Considering Modern Headlamp Performance
Transportation Research Record, 2008Co-Authors: H Gene Hawkins, Madhuri GogulaAbstract:For more than 50 years, headlight sight distance has been one method for calculating the length of sag vertical curves; the others are passenger comfort, drainage control, and general appearance. The headlight sight distance is based on a 1° upward divergence of the Headlamp beam. Over the past 20 years, Headlamps have transitioned from being 100% sealed beam to modern replaceable bulb Headlamps that project less light above the horizontal plane than the sealed-beam Headlamps that are the basis for sag curve design. This paper describes theoretical and field measurements of the illuminance levels provided by sealed-beam and modern Headlamps. The results of the analysis indicate that modern Headlamps provide significantly less light above the horizontal than sealed-beam Headlamps, indicating a potential need to modify the design equations for sag vertical curves. According to the theoretical analysis, the upward divergent Headlamp angle used in the sag curve design equation should be reduced from 1° to bet...
-
How Modern Headlamp Performance Impacts Sag Vertical Curve Design
Journal of Transportation Engineering, 2007Co-Authors: H Gene HawkinsAbstract:For over 50 years, the basis for calculating the length of sag vertical curves has been the sight distance based on a 1° upward divergence of the Headlamp beam. Over the last 20 years, Headlamps have transitioned from being 100% sealed beam to modern replaceable bulb Headlamps that project less light above the horizontal plane compared to the sealed beam Headlamps that are the basis for the sag curve design. This paper analyzes the performance of modern Headlamps with respect to sag vertical curve design by calculating the amount of illumination reaching the pavement in a sag curve. The analysis indicates that the Headlamp beam angle used to calculate sag curve length should change from 1 to 0.75° to provide an illuminance level with modern Headlamps that is equal to the illuminance provided by sealed beam Headlamps. Such a change would increase the K values for sag curve design from 13, 30, and 55 to 15, 37, and 70 for design speeds of 110, 80, and 50 km/h, respectively.
-
Headlamp luminous intensity matrix adjustment factors for modeling traffic sign performance
SAE transactions, 2005Co-Authors: H Gene Hawkins, Paul J Carlson, Susan T ChryslerAbstract:There have been a series of recent national activities that have increased the awareness of performance of traffic signs at night. Also, transportation agencies now have more choices than ever in the selection of retroreflective sign sheeting materials for traffic signs. Accompanying these changes is an increased ability to model the photometric performance of sign materials and predict the luminance that associated with a specific set of conditions. The Headlamps may be the one factor that is the most idealized parameter in the photometric modeling process. This paper reviews work on traffic sign luminance modeling and describes how Headlamp photometric data are used in these models. It also describes illuminance measurements made of a sample of 46 U.S. passenger cars and light trucks with clean and dirty Headlamps. Subsequent modeling of Headlamp performance, including an assessment of the impact of dirt on sign luminance is described. Recommendations are presented that can be used to adjust Headlamp luminous intensity matrices to yield candela levels at typical sign geometries representing measured candelas from a pseudo random selection of vehicles.
Susan T Chrysler - One of the best experts on this subject based on the ideXlab platform.
-
Headlamp luminous intensity matrix adjustment factors for modeling traffic sign performance
SAE transactions, 2005Co-Authors: H Gene Hawkins, Paul J Carlson, Susan T ChryslerAbstract:There have been a series of recent national activities that have increased the awareness of performance of traffic signs at night. Also, transportation agencies now have more choices than ever in the selection of retroreflective sign sheeting materials for traffic signs. Accompanying these changes is an increased ability to model the photometric performance of sign materials and predict the luminance that associated with a specific set of conditions. The Headlamps may be the one factor that is the most idealized parameter in the photometric modeling process. This paper reviews work on traffic sign luminance modeling and describes how Headlamp photometric data are used in these models. It also describes illuminance measurements made of a sample of 46 U.S. passenger cars and light trucks with clean and dirty Headlamps. Subsequent modeling of Headlamp performance, including an assessment of the impact of dirt on sign luminance is described. Recommendations are presented that can be used to adjust Headlamp luminous intensity matrices to yield candela levels at typical sign geometries representing measured candelas from a pseudo random selection of vehicles.
-
Headlamp ILLUMINATION PROVIDED TO SIGN POSITIONS BY U.S. VEHICLES
2002Co-Authors: Susan T Chrysler, Paul J Carlson, H G HawkinsAbstract:Night traffic sign visibility is largely determined by luminance. Sign luminance (SL), in turn, is determined by viewing geometry, retroreflective aspects of the sign material, and Headlamp illumination. In recent years, computer modeling of SL has advanced allowing SL to be predicted based on data sets of retroreflective material performance and Headlamp luminous intensity matrices. The vast majority of the Headlamp data for these computer models are luminous intensity values at specific horizontal and vertical test points as measured on a goniometer in a photometric range. This approach removes the Headlamp from its natural mounting on the vehicle. Some researchers have gone a step further removed from an actual vehicle. To address this data gap, the Texas Transportation Institute measured vehicle Headlamp illuminance at prespecified points representing typical sign locations. The vehicles were measured without aiming or cleaning the Headlamps. Illuminance data will be presented via descriptive statistics and used to calculate luminance for a retroreflective sign in that position.
-
PROPOSAL FOR STANDARD U.S. Headlamp BEAM PATTERN FOR EVALUATION OF RETROREFLECTION
Transportation Research Record, 1994Co-Authors: Theodore J Szczech, Susan T ChryslerAbstract:Confusion arises among researchers and designers when different Headlamp output data files are used to produce luminance profiles of retroreflective sheeting. It is proposed that a standard U.S. Headlamp data file be established to reduce confusion and improve communication among researchers in the area of retroreflective materials. A composite 15th percentile Headlamp data file for calculating luminance values for which 85% of sampled Headlamps produce equal or greater luminance is offered. The calculation of luminance depends on Headlamp performance and retroreflector characteristics. Use of this 15th percentile Headlamp is justified by comparison of luminance values calculated for enclosed lens sheeting for various Headlamp data files. This reference Headlamp is intended as a standard for retroreflective material research. It is not intended to be a design target for the development or testing of new Headlamps. The Headlamp data file is available on request.
John D. Bullough - One of the best experts on this subject based on the ideXlab platform.
-
Benefits of Intelligent Headlamp Technologies to Pedestrian Safety at Roundabouts
2012Co-Authors: John D. Bullough, Nicholas P. SkinnerAbstract:A two-part study of the influence of vehicle Headlamps and roadway lighting on the ability of drivers to see pedestrians along crosswalks in roundabout intersections was conducted. In the first part of the study, the photometric performance of vehicle Headlamp systems including conventional halogen and high intensity discharge (HID) low-beam Headlamp systems and intelligent vehicle Headlamp systems that might provide optimized illumination for navigating through roundabouts was compared. Relative visual performance analyses based on these comparisons were used to demonstrate when such vehicle Headlamp technologies might offer benefits in terms of pedestrian safety and efficient navigation. In the second part of the study, an outdoor field experiment was conducted to assess observers' ability to detect and identify the walking direction of pedestrian targets in the field of view. Importantly, this experiment utilized many of the same conditions and geometric characteristics that were evaluated in the photometric simulation, and included calculations of visual performance. A secondary objective of the studies summarized in this report was to validate the use of visual performance modeling to predict driver visibility under conditions corresponding to illumination from vehicle Headlamps and fixed roadway lighting.
-
Efficacy of wipers-on, Headlamps-on legislation
Safety Science, 2012Co-Authors: John D. BulloughAbstract:Empirical evidence for the benefit of so-called wipers-on, Headlamps-on legislation, requiring drivers to use vehicle Headlamps when windshield wipers are on, is nonexistent. An evaluation of fatal, multi-vehicle crashes during daytime and nighttime in clear and rainy weather was made, for states in the US that have recently enacted such legislation, and for which crash data are available. Results indicate a statistically reliable reduction in the incidence of fatal, multi-vehicle crashes during daytime in these states relative to nighttime, when Headlamp use would not be expected to differ before and after enactment of wipers-on, Headlamps-on legislation.
-
Survey of the Current State of Vehicle Headlamp Aim
2010Co-Authors: Nicholas P. Skinner, John D. Bullough, Aaron M SmithAbstract:A study of vehicle Headlamp vertical aim was undertaken to determine the extent to which mis-aim exists in a sample of American-owned vehicles. In addition to Headlamp aim measurement, additional information (e.g., age, physical condition, vehicle type, source type, and optical design) was collected for more than 120 vehicles representing in-use and new vehicles. On average, Headlamps for currently registered vehicles were aimed slightly downward, and for new vehicles were aimed close to the nominally correct alignment. However, 60% of currently registered vehicles had at least one Headlamp aimed outside the tolerances allowed by the standards of the Society of Automotive Engineers, consistent with the results of previous studies. Approximately 45% of the new vehicles measured had at least one Headlamp mis-aimed. There were not any statistically reliable relationships between vertical mis-aim and vehicle age, vehicle type, Headlamp optical systems or Headlamp source (i.e., halogen versus high intensity discharge). Based on the samples measured, it would be relatively common to find Headlamps that produce high light levels above a horizontal plane containing the light source in the Headlamps due to mis-aim. Proper aim of Headlamps would probably reduce the likelihood of Headlamp glare and improve driver visibility on American-owned vehicles.
-
Sensitivity Analysis of Headlamp Parameters Affecting Visibility and Glare
2008Co-Authors: Yukio Akashi, John D. BulloughAbstract:Computer-simulated evaluations were conducted to identify the extent to which driver visibility and glare are affected by Headlamp light source type (e.g., tungsten-halogen or high-intensity discharge), mounting height, optical system type, alignment type, and mis-aim. Based on the results of these simulation evaluations, this study also addressed whether further limits might be considered in photometric standards for Headlamps that are addressed by Federal regulations. While there appears to be an inherent conflict between visibility and glare in the photometric design of Headlamps, the analyses performed here do indicate that current photometric specifications for Headlamps do not always trade off visibility and glare equally (e.g., Headlamps that provide equivalent forward visibility as characterized here can result in different levels of disability or discomfort glare). The findings imply that advanced (dynamic) forward-lighting systems (AFS), if they can be made practical, might be of benefit in adjusting Headlamp luminous intensity distributions in various situations to maximize visibility while controlling glare within acceptable limits.
-
Assessment of Headlamp glare and potential countermeasures : the effects of Headlamp mounting height
2008Co-Authors: Yukio Akashi, John Van Derlofske, Ramesh Raghavan, John D. BulloughAbstract:This project examined the effects of Headlamp mounting height on the disability and the sensation of discomfort caused by glare. This was performed through a field study and a simulation study. In the field study, subjects evaluated the degree of glare from oncoming and following Headlamps with different mounting heights and different intensity of Headlamps. This field study provides data to suggest how Headlamp mounting height affects discomfort glare. Additionally, to examine disability glare, two simulation analyses were also performed through calculations using existing models. One analyzed drivers’ reaction times to peripheral targets. The other analyzed detection distances to small targets located along the roadway. Both analyses treated Headlamp mounting height as one of several independent variables. Overall, this project led to the conclusion that the mounting height of oncoming Headlamps affects both disability glare and discomfort glare. A common tendency is that as the mounting height increases, glare is also increased. The increase in glare results in increased discomfort and reduction of visual performance (i.e., increased reaction times to detect objects and decreased detection distances).
Ahmed Samir - One of the best experts on this subject based on the ideXlab platform.
-
Vehicle Sensing and Communications using LED Headlights to Enhance the Performance of Intelligent Transportation Systems: Proof of Concept, Implementation, and Applications
LSU Digital Commons, 2019Co-Authors: Ekin Sabit, Ahmed SamirAbstract:This project investigates the use of vehicle light-emitting diode (LED) Headlamp devices for improving the accuracy and reliability of traffic (sensing and communication) data measurements required for developing effective intelligent transportation systems (ITS) technologies and solutions. Vehicular communication and sensing technologies are mainly based on conventional radio frequency (RF) or laser technologies. These systems suffer from several issues such as RF interference and poor performance in scenarios where the incidence angle between the speed detector and the vehicle is rapidly varying. Introducing a new sensing technology will add diversity to these systems and enhance the reliability of the real-time data. In this project, we proposed and investigated a novel speed estimation sensing system named “Visible Light Detection and Ranging (ViLDAR)” (patent pending). ViLDAR utilizes visible light-sensing technology to measure the variation of the vehicle’s Headlamp light intensity to estimate the vehicle speed. Similarly, visible light sensing technology is used for data communication purposes, where the vehicle Headlamp is utilized for wireless data transmission purposes. This project outlines the ViLDAR system simulations, implementation including hardware and software components, experimental evaluation in both laboratory and outdoor environments. The experimental measurement settings of the ViLDAR experiments are detailed. Encouraging results for both sensing and communication scenarios are obtained. The outcome of this proof-of-concept study both in the laboratory and outdoor validates the merit of the proposed technology in speed estimation (sensing) and data communication. The outcomes of this project will inspire a wide and diverse range of researchers, scientists and practitioners from the ITS community to explore this new and exciting technology. This project built initial steps in exploring this new sensing and communication modality using vehicle Headlamps, leaving open a wide field for exploration and novel research
-
Vehicle Sensing and Communications using LED Headlights to Enhance the Performance of Intelligent Transportation Systems: Proof of Concept, Implementation, and Applications
LSU Digital Commons, 2019Co-Authors: Ekin Sabit, Ahmed SamirAbstract:Corresponding data set for Tran-SET Project No. 18ITSOKS01. Abstract of the final report is stated below for reference: This project investigates the use of vehicle light-emitting diode (LED) Headlamp devices for improving the accuracy and reliability of traffic (sensing and communication) data measurements required for developing effective intelligent transportation systems (ITS) technologies and solutions. Vehicular communication and sensing technologies are mainly based on conventional radio frequency (RF) or laser technologies. These systems suffer from several issues such as RF interference and poor performance in scenarios where the incidence angle between the speed detector and the vehicle is rapidly varying. Introducing a new sensing technology will add diversity to these systems and enhance the reliability of the real-time data. In this project, we proposed and investigated a novel speed estimation sensing system named “Visible Light Detection and Ranging (ViLDAR)” (patent pending). ViLDAR utilizes visible light-sensing technology to measure the variation of the vehicle’s Headlamp light intensity to estimate the vehicle speed. Similarly, visible light sensing technology is used for data communication purposes, where the vehicle Headlamp is utilized for wireless data transmission purposes. This project outlines the ViLDAR system simulations, implementation including hardware and software components, experimental evaluation in both laboratory and outdoor environments. The experimental measurement settings of the ViLDAR experiments are detailed. Encouraging results for both sensing and communication scenarios are obtained. The outcome of this proof-of-concept study both in the laboratory and outdoor validates the merit of the proposed technology in speed estimation (sensing) and data communication. The outcomes of this project will inspire a wide and diverse range of researchers, scientists and practitioners from the ITS community to explore this new and exciting technology. This project built initial steps in exploring this new sensing and communication modality using vehicle Headlamps, leaving open a wide field for exploration and novel research
