Browsing by Author "Terry, Travis N."

Now showing 1 - 9 of 9
  • Thumbnail Image
    Applicability of mesopic factors to the driving task
    Gibbons, Ronald B.; Terry, Travis N.; Bhagavathula, Rajaram; Meyer, Jason E.; Lewis, A. (SAGE, 2016-02-01)
    With the advent of light-emitting diode technology being applied to roadway lighting, the spectral power distribution of the light source is becoming much more important. In this experiment, the detection of pedestrians at five adaptation levels under three light sources, high pressure sodium and light emitting diodes of two colour temperatures was measured in realistic roadway scenarios. The results show that while the light source type was not significant, an increase in adaptation luminance increased the detection distance. As the offset of the object to the roadway increased, some spectral effects became more significant; however, this effect was not consistent across all angles of eccentricity. The conclusions from this work indicate that mesopic factors may not be applicable on high-speed roads.
  • Thumbnail Image
    Assessment of the Effectiveness of Emergency Lighting, Retroreflective Markings, and Paint Color on Policing and Law Enforcement Safety
    Terry, Travis N. (Virginia Tech, 2020-07-01)
    This project is an in-depth investigation on the impact of lighting, marking and paint schemes on the operational aspects of police vehicles. This investigation consisted of two phases that ultimately consisted of four experiments. An array of lighting and marking schemes were implemented on police vehicles in a variety of jurisdictions for evaluation. The study then investigated the change in the visibility of police officers, the public reaction to these schemes, and the operational impacts of these systems. The first phase of the project was a naturalistic observation study where the goal was to better understand how traffic behaved around traffic stops. Test vehicles were positioned in simulated traffic stops and patrol locations to determine how traffic behavior was affected by various configurations of police lighting and markings. Camera and radar systems were used to measure the changes in driver speed and when drivers responded to the move over law. Based on the results of the naturalistic studies, the impact of the lighting system on officer visibility was investigated in a controlled human factors test where the ability of a driver to see a police officer outside of their vehicle was measured in the presence of the lighting systems. The purpose of this interjected effort was to verify that the experimental schemes would not increase risk to law enforcement despite data from the first phase indicating the vehicles were more visible. A second part to that study evaluated conventional methods of bolstering an officer's visibility outside of their vehicle at night. The second phase took the findings of the first phase and implemented changes to several police vehicles from local and state agencies to be in operation for at least 18 months. This was to assess the rate of near-misses and crash rate to relate the vehicle changes to law enforcement safety. Additionally, rates of citations were assessed, and surveys offered an opportunity for law enforcement to provide their own feedback on the implementations. The lighting systems evaluated included a completely blue lighting system, an enhanced all blue lighting system with twice the light output, a red and blue system, and a single flashing blue beacon. In terms of markings, retroreflective markings along the side of the vehicle, a retroreflective contour line, chevrons on the rear of the vehicle and unmarked vehicles were evaluated. Finally, a variety of vehicle colors were used to investigate the impact of the base vehicle paint color. The results indicate that both the red and blue lighting system and the high output blue lighting system increase the distance at which drivers moved over significantly. In general, at least 95% of traffic attempted to merge away from an actively lighted police vehicle, when possible. In terms of the speed change, drivers began reducing their speed by approximately 600 m from the police vehicle. Similarly, the addition of retroreflectivity to the rear of the vehicle showed an additional benefit for causing drivers to move over sooner. However, these benefits came at a cost to the officer's visibility. When outside of their vehicle, the high output blue system significantly reduced officer detectability while the red and blue configuration only impacted detection distance by 3 meters. The investigation did find that these impacts could be overcome with retroreflective vests worn by the officers. In the second phase, a preference revealed by officers favored the red-blue configuration. They stated that this configuration provided greater comfort for them and less glare to approaching drivers. The study also revealed that the alternative configurations did not impact the operational activities of police authority.
  • Thumbnail Image
    Assessment of the impact of color contrast in the detection and recognition of objects in a road environment: final report
    Terry, Travis N.; Gibbons, Ronald B. (National Surface Transportation Safety Center for Excellence, 2011-12-16)
    With the development of new light sources, options for the color and spectral output of a luminaire are wider than for traditional light sources. This can impact visibility as the spectral output of a light source may have a significant impact on the appearance of objects in the roadway environment. This study compares the visibility and color contrast afforded by three separate roadway luminaire types, each with a different spectral output. The benefit provided by the additional color information provided by the spectral distribution of a luminaire can improve detection of objects in the roadway by as much as 50%. These results, however, are not consistent across all spectral output and object color combinations. These results also indicate that the proper selection of a luminaire output will provide better visibility for the driver. -- Report website.
  • Thumbnail Image
    Comparing LED Lighting Systems in the Detection and Color Recognition of Roadway Objects
    Terry, Travis N. (Virginia Tech, 2011-05-11)
    This study compared two LED luminaires and their abilities to provide detection distance and color recognition distance of potential roadway hazard. Detection distance is regarded as a metric of visibility. Color recognition distance is a metric for comparing the impact of the (Correlated Color Temperature) CCT of each luminaire and their color contrast impact. Mesopic vision, the mode of vision most commonly used for night driving, was considered in this study. Off-axis objects were presented to participants to assess the peripheral abilities of the luminaires. The impacts of luminance and color contrast were addressed in this study. The experiment was performed on the Virginia Smart Road where standard objects of different colors and pedestrians wearing different colors were detected by drivers of a moving vehicle in a controlled environment. The key difference between the two luminaires was their color temperatures (3500K versus 6000K). The results indicated that neither light source provided a significant benefit over the other although significant interactions were found among object color, age, and lighting level. The results indicate that the luminaires provide similar luminance contrast but their color contrasts depend heavily on the color temperature, the object, and the observer. This study followed the protocol developed by the Mesopic Optimisation of Visual Efficiency (MOVE) consortium developed by the CIE for modeling mesopic visual behavior.
  • Thumbnail Image
    Evaluation of Guardrail Embedded Lighting System in Trinidad, Colorado
    Terry, Travis N.; Gibbons, Ronald B. (Colorado. Department of Transportation. Research Branch, 2014-02)
    This report provides information on the design considerations of the embedded highway lighting design on Interstate-25 in Trinidad, Colorado, in terms of visibility. The information is based on visibility characterizations of small targets using luminance, illuminance, and contrast calculations as well as participant input on the detectability of small targets. Experimental conditions included two different aim angles of the lighting design (forward and cross) as well as two small target colors (red and blue). When compared to the small target detection distances produced by conventional overhead lighting systems in previous studies, the research determined that the small target visibility distances of the embedded lighting design to be shorter by approximately 50%. Adjustments to the spacing, aim, and breadth of the lighting design are recommended for future research considerations. Implementation The results of this research indicate the lighting design is an alternative; however, additional considerations to the beam angle, beam width, beam height, and spacing may improve the implementation of the system.
  • Thumbnail Image
    Examination of the Current Practice of Lighting in Virginia: Nighttime Work Zones and Improving Safety Through the Development of Nighttime Lighting Specifications
    Bhagavathula, Rajaram; Gibbons, Ronald B.; Medina, Alejandra; Terry, Travis N. (Virginia Transportation Research Council, 2017-09)
    This project evaluated current nighttime work zone lighting practices for limited-access highways and primary routes in Virginia through (1) an on-site evaluation of lighting levels in work zones; (2) an illuminance characterization of various commercially available light towers; and (3) a human factors evaluation of those light towers and developed effective nighttime work zone lighting requirements for Virginia. The majority of the static nighttime work zones used metal halide portable light towers. Mobile operations such as milling and paving used equipment-mounted balloon lights and LEDs. Horizontal illuminance levels in the work zones were affected by the number of light towers, locations of the light towers, and number of traffic lanes in the work zone. The measured horizontal illuminance levels in the work zones were much higher than recommended levels. Milling and paving operations that used equipment-mounted lights had lower illuminance levels than operations that used portable light towers. Vertical illuminance levels in the traffic lane were significantly affected by the aiming of the luminaires on the portable light towers. Luminaires aimed into the traffic travel lane produced higher vertical illuminance levels, which can result in disability and discomfort glare and consequently reduce visibility. The visual performance of drivers in a work zone can be influenced by the type and orientation of the light tower. An orientation aimed toward the driver resulted in lowering drivers’ visual performance, both objectively and subjectively. This decrease in visual performance could be attributed to higher vertical illuminance. To increase the drivers’ visual performance and reduce glare in the work zone, efforts should be taken to aim the light towers in an active nighttime work zone away from the direction of traffic or perpendicular to it. In these orientations, all the three light towers tested had similar visual performance measures. The increase in the mean vertical illuminance level in the critical range is associated with higher perceived ratings of glare. Results showed that the mean vertical illuminance in the distance range of 260 to 65 ft to the light tower could be used as an objective measure of glare. A mean vertical illuminance of less than 17 lux resulted in lower perceived glare ratings. Results also indicated that light towers should be oriented so that the angle between the beam axis and driver line-of-sight axis is always greater than or equal to 90 degrees. Finally, a draft specification outline including a plan for on-site lighting evaluation of a work zone is presented.
  • Thumbnail Image
    Moth Effect: Determining Contributing Factors
    Terry, Travis N. (National Surface Transportation Safety Center for Excellence, 2018-01-31)
    The “moth effect” theory posits that drivers are attracted to or mesmerized by light much as moths are drawn to a flame. The notion that drivers are susceptible to the moth effect is born from the fact that vehicles stopped on the shoulder of a roadway are often struck by passing motorists, despite being obviously lighted and outside the lane of travel. There is very little practical highway transportation research on the moth effect, largely due to the difficulty of capturing the effect in a controlled setting. In fact, there is very little hard evidence that the effect exists at all. Even when a crash is speculated to be a result of the moth effect, that term is never used in an accident report. Therefore, circumstances surrounding crashes that could be a result of the moth effect are largely unknown. The goal of this research was to incorporate previous successful attempts at studying the moth effect. Research included tactics such as building fatigue, utilizing flashing versus steady lights, creating tasks with vehicles parked on the shoulder, and utilizing eye-tracking technology to determine gaze fixation and duration. The experiment carried out in this research effort was essentially a series of pilot studies where variables such as following distance, following duration, behavior of the lead vehicle, and the lead vehicle’s rear lights were varied from participant to participant with the goal of eliciting a moth effect and determining the variables that may have caused it. A moth effect behavior was defined as an instance when the participant driver left the lane of travel and steered toward a lead vehicle that had moved to the shoulder. There were a number of obstacles to overcome when researching the moth effect. For instance, despite the belief that driver over-fatigue and inebriation are major contributors to the effect, it was not feasible to permit over-fatigued or inebriated subjects to drive a vehicle as part of an experiment. To address fatigue’s contribution to the moth effect, this experiment immediately followed a separate experiment that involved participants driving for over an hour. Following the first experiment, those same participants were fitted with a calibrated eye tracker and asked to drive for another hour with the intent of causing more fatigue. The moth-effect experiment resulted in 1 of 21 participants exhibiting a moth-effect-like steering behavior. Factors contributing to this behavior included a close following distance to a lead vehicle (~100 feet), flashing hazard lights on the lead vehicle, and the participant not wearing an eye-tracking device. The participant exhibiting the moth-effect behavior, like other participants, experienced fatigue from the driving task, which involved driving for nearly an hour at 35 mph with the absence of radio, conversation, or any other tasks apart from following a lead vehicle. The authors believe that reduced alertness, akin to “highway hypnosis” (in which the driver operates the vehicle in a drowsy, trance-like state), may have also contributed to the driver’s behavior.
  • Thumbnail Image
    Problematic Roadway Environments for Automated Vehicles
    Terry, Travis N.; Tanner, Stephen (National Surface Transportation Safety Center for Excellence, 2018-04-03)
    Progress in the area of automated vehicles (AVs) will benefit safety, mobility, and environmental sustainability. Of the roughly 30,000 traffic-related fatalities reported yearly, 94% are due to human error. AVs replace the human element of driving with sensors, cameras, actuators, and algorithms and aim to drastically reduce crashes and associated fatalities. The advent of AVs is also predicted to increase mobility by reducing congestion via ride sharing and more deliberate AV-performed navigation procedures. AVs are also expected to reduce fossil fuel use and improve urban land usage, resulting in positive economic and environmental sustainability effects. AV-related policies and laws are beginning to taking shape, and already differ between some states. While forward-thinking can be beneficial, the consequence of having non-overlapping laws and policies regarding AVs is a potential issue. A complete survey of laws, standards, and regulations regarding AVs for each state is outside of the scope of this project. However, as of the time of this report, 21 states had enacted AV policies, some which impact the testing and regulation of AV technology. Rigorous testing often proves to be a challenge since AV technologies can differ based on a vehicle’s manufacturer, each of whom provides their own suite of systems to perform the autonomous tasks. It is the potential failure of these systems to perform in certain scenarios that impedes progress, both in terms of AV development and policy. This effort seeks to capture, classify, and distribute real-world scenarios that could be problematic for AVs. The developed Visually Confusing Automated Vehicle (VCAV) database of videos, which is available via an online interface, highlights specific elements of the roadway, such as improper lane markings, that AV technology relies upon for guidance. The goal of the VCAV is to promote research in specific areas regarding these scenarios and to inform policymakers, manufacturers, designers, and Departments of Transportation about problematic scenarios. At the time of this report, the database consisted of approximately 12 hours of recorded scenarios. Most scenarios were recorded on restricted-access highways, such as interstates, which are a likely domain for early deployment of highly automated AVs. Other focus areas include inclement weather and any work zone activity. Because these scenarios are often problematic for human drivers, it is important that AVs outperform their counterparts in these situations. The VCAV can be found online at visualconfusion.vtti.vt.edu and will require user login and registration. Once granted access, users can leverage the database to sort by types of scenarios, such as improper lane markings, types of work zones, and video duration. Researchers will continue to curate and manage the database as time and personnel resources allow. More scenarios will be added and categorized within the database as they become available.
  • Thumbnail Image
    Rural Intersection Lighting Safety Analysis
    Bhagavathula, Rajaram; Gibbons, Ronald B.; Terry, Travis N.; Edwards, Christopher J. (National Surface Transportation Safety Center for Excellence, 2017-08-03)
    Under the sponsorship of the National Surface Transportation Safety Center for Excellence (NSTSCE), this research studied the relationship between lighting level and the night-to-day (ND) crash ratio at rural intersections in the state of Virginia. Most existing research on intersection lighting indicates that the presence of lighting reduces night crashes. This study aimed to quantify the effect of lighting level and lighting quality on ND crash ratios at rural intersections. Lighting data were collected from 131 rural intersections in Virginia, and crash data for the intersections were obtained from the Virginia Department of Transportation (VDOT). Lighting data were collected using a Roadway Lighting Mobile Measurement System (RLMMS). Out of the 131 intersections, data from 99 intersections were used for the comparative analysis. Data from 32 intersections could not be used because of issues with lighting data (e.g., Global Positioning System, illuminance data dropouts). Negative binomial regression was used to model the crash and lighting data. The results showed that increasing the average horizontal illuminance at all the intersections (both lighted and unlighted) by one unit (1 lux) decreased the ND crash ratio by 7%. For the lighted intersections, the same increase in average horizontal illuminance decreased the ND crash ratio by 9%. The largest decrease in the ND crash ratio was for unlighted intersections, where a 1-lux increase in the average horizontal illuminance decreased the ND crash ratio by 21%. The average roadway luminance also had negative parameter estimates, indicating that an increase in average roadway luminance results in a lower ND crash ratio. Stop-controlled intersections had smaller ND crash ratios compared to signalized intersections. Intersections with a posted speed limit of less than or equal to 40 mph had lower ND crash ratios compared to intersections with a posted speed limit higher than 40 mph. Results also showed that most lighting levels at most rural intersections did not meet the standards recommended by the Illuminating Engineering Society of North America (IESNA).