Browsing by Author "Williams, Brian M."

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    4U Lighting – Cooperative Headlighting
    Palmer, Matthew; Tsuda, Hiroshi; Williams, Brian M.; Gibbons, Ronald B. (National Surface Transportation Safety Center for Excellence, 2019-10-31)
    The purpose of this project was to evaluate the effectiveness of an alternative cooperative headlighting method, dubbed 4U Lighting. A human-subjects study was conducted in which 12 participants 65 or older observed pedestrians under different lighting configurations and identified the moment when they were sure they could see a pedestrian. The participants drove a vehicle towards a static vehicle in the opposite lane around which the pedestrians were located. The distance at which participants could detect the pedestrian, termed the detection distance, was compared across lighting conditions and served as the measure of improvement in driver visual performance (visibility). Commercial connected vehicle hardware and protocols were used to communicate position between the two vehicles and to trigger the operation of the custom lighting control system. The system operated as expected and the data showed benefits to driver visual performance.
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    Active and Adaptive Roadway Delineation Systems
    Williams, Brian M.; Gibbons, Ronald B.; Flintsch, Alejandra Medina (National Surface Transportation Safety Center for Excellence, 2017-10-13)
    Heavy fog presents a significant safety hazard to drivers by reducing their ability to see the roadway and other vehicles. Even so, drivers often fail to adjust their speed to account for the reduced visibility, resulting in stopping distances that exceed visibility distance. Active delineators, or in-pavement light emitting diode (LED) markers, are an emerging technology which can be used to assist drivers in traveling through fog-prone areas by marking road or lane boundaries. However, there is a lack of research indicating how the presence of active delineators might also affect a driver’s behavior. This study sought to examine how the presence of active delineators in fog might affect drivers’ speed. Three lighting patterns and two brightness levels were tested. In daytime conditions, the delineators had no effect on speed. During nighttime conditions, participants often drove faster when the active delineators were present. Participants felt that the active delineators were helpful for navigating through the fog in both daytime and nighttime conditions, but preferred the higher brightness settings in the daytime.
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    The Assessment of Alternative Overhead Sign Lighting
    Williams, Brian M.; Gibbons, Ronald B. (National Surface Transportation Safety Center for Excellence, 2020-07-22)
    This report evaluates an alternative method for lighting highway signs that takes advantage of their retroreflective properties. This method uses a single luminaire mounted some distance upstream of the sign, with a focused, but evenly distributed beam so that the sign always receives the same amount of illumination. To evaluate the proposed system, a human-subjects experiment was performed on the Virginia Smart Road to test two sign configurations: an overhead sign mounted on a gantry above the highway and a sign mounted at the side of the road on a horizontal curve. For the overhead sign, there were no statistical differences between the upstream lighting, traditional style lighting, and headlamp-only conditions, though there was an increase in the mean legibility distance of the sign (~14 m) when the upstream luminaire was located on the shoulder of the road at the highest luminance setting. For the horizontal curve, upstream lighting provided no benefit for sign legibility due to the ambient lighting in the vicinity, but placing the luminaire closer to the sign (approximately 20 m) resulted in more consistent luminance from a wider range of viewing angles. Although upstream lighting provided legibility distances similar to traditional sign lighting, it may offer advantages due to reduced maintenance and energy costs.
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    Assessment of the Durability of Wet Night Visible Pavement Markings: Wet Visibility Project Phase IV
    Gibbons, Ronald B.; Williams, Brian M. (Virginia Center for Transportation Innovation and Research, 2012-06)
    This project encompassed a research effort to establish the durability of pavement markings in an on-road installation. Six marking technologies were installed on a portion of Route 460 in Blacksburg, Virginia. A human factors experiment in natural rain conditions was performed to establish the visibility needs of the driver. The retroreflectivity of the markings was measured at intervals of 2 to 5 months, with six measurements over the course of 23 months. The numbers of snow plow crossings and chemical treatments were also measured. Although all markings lost a considerable amount of retroreflectivity after the first winter, the markings installed in grooves or in rumble strips were shown to retain more retroreflectivity and receive less damage than markings installed on the surface of the roadway. Twenty-three months after installation, the retroreflectivity for all markings in active rain conditions had dropped below the 150 mcd/m2/lx minimum recommended from previous research. The reflective tape was the closest to maintaining the minimum with a mean retroreflectivity of 137mcd/m2/lx in 1 in/hr rain. Several other markings maintained a retroreflectivity above 84 mcd/m2/lx; this may still provide a benefit over standard paint. The study recommends that VDOT's Traffic Engineering Division install pavement markings in grooves or in rumble strips. VDOT will determine where the use of grooves or rumble strips is appropriate. Because pavement marking visibility is more critical for high-speed roadways such as interstate roadways and major arterials, these roads should be the highest priority. Grooved markings may also be desired for high-volume roadways where markings may be exposed to higher levels of wear from traffic. The study markings on Route 460 in Blacksburg should be monitored for two more years. The study team should make the measurements after each winter through 2013 and report the findings to VDOT in a brief report. VDOT staff should perform additional cost-benefit analyses to address standard VDOT policy, procedures, and practices and possible supplier warranties.
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    Bicycle Visibility: Conspicuity of Bicycle Headlamps, Tail Lamps, and Retroreflective Garments in Nighttime Roadway Environments
    Bhagavathula, Rajaram; Gibbons, Ronald B.; Williams, Brian M.; Connell, Caroline A. (National Surface Transportation Safety Center for Excellence, 2020-07-21)
    Cyclist deaths are overrepresented among traffic fatalities, and increasing cyclist conspicuity to drivers could potentially reduce cyclist deaths, particularly at night. This report describes an experiment with various commercially available bicycle visibility-enhancement systems in terms of their conspicuity to drivers during the day and at night. Visibility enhancements included a headlamp, tail lamp, spoke lights, and retroreflective clothing, including garments that highlight biomotion. The results indicate that active visibility treatments, such as bicycle-mounted lights, make cyclists more conspicuous than passive systems like retroreflective vests and biomotion bands. Flashing headlamps and tail lamps were the most conspicuous treatments during both the day and at night; fast flashing headlamps (6.7 Hz) had higher detection distances and rates during the day, and moderately fast flashing headlamps (3.4 Hz) had higher detection distances and rates at night. Spoke lights and flashing tail lamps, along with retroreflective vests, also aided cyclist visibility during the day and at night, especially for vehicles approaching intersecting cyclists. Passive retroreflective visibility treatments were most effective at night, when the vehicle was passing the cyclist from behind. However, that approach also used reflectors, so the discrete effect of passive retroreflective treatments could not be determined. This study also found that biomotion markers alone do not significantly increase cyclist conspicuity in visually complex natural environments. For most approaches, flashing lights had greater detection distances than biomotion markers, which in turn had higher detection rates than headlamps and tail lamps.
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    Evaluation of Innovative Approaches to Curve Delineation for Two-Lane Rural Roads
    Gibbons, Ronald B.; Flintsch, Alejandra Medina; Williams, Brian M.; Li, Yingfeng; Machiani, Sahar Ghanipoor; Bhagavathula, Rajaram (Virginia Transportation Research Council, 2018-06)
    Run-off-road crashes are a major problem for rural roads. These roads tend to be unlit, and drivers may have difficulty seeing or correctly predicting the curvature of horizontal curves. This leads to vehicles entering horizontal curves at speeds that are too high, which can often lead to vehicles running off the roadway. This study was designed to examine the effectiveness of a variety of active and passive curve warning and curve delineation systems on two two-lane rural roads to determine which is the most effective at reducing vehicle speeds and assisting lane-keeping. The study consisted of a human-factors study, as well as an observational study. There were nine curves examined in the study on two road sections in Southwest Virginia. The human-factors study included participants whose speed and lane position were tracked as they drove through eight curves, both before and after new treatments were installed in each of the eight curves. The observational study examined the speed and lane position of traffic on all the curves before and after the installation of the new treatments. The observational study included a curve on a road near the primary study section. The results of the study were mixed, with every tested system leading to some reductions in speed or encroachments at some parts of the curve while also leading to increases in the same values at other parts of the curve. No clear difference was discovered between passive and active systems or between delineation and warning systems. The study recommends that in addition to a safety assessment, specific curve characteristics and budget should be the main considerations in the selection of a treatment for a curve.
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    Pedestrian Visibility in Roundabouts: Naturalistic Study of Driver Eye-Glance Behavior
    Bhagavathula, Rajaram; Williams, Brian M.; Gibbons, Ronald B. (National Surface Transportation Safety Center for Excellence, 2019-04-16)
    Roundabouts increase safety, but their safety effects on vulnerable road users are not as great as the safety effects for motor-vehicle drivers. Additionally, many motorists fail to yield to pedestrians at intersections and roundabouts, possibly because drivers do not see the pedestrians, crosswalk signage, and/or pavement markings. Eye-tracking technology has been used to quantify driver eye-glance behavior in a variety of driving contexts, but has yet to be applied to drivers in roundabouts with pedestrians. The exploratory research performed for this project attempted to shed light on driver visual behavior at roundabouts, and to examine the extent that drivers looked at pedestrians, with the ultimate goal of increasing pedestrian safety at roundabouts. A quasi-naturalistic experimental study was conducted and drivers’ mean fixation durations toward pedestrians located at crosswalks were measured at two different roundabouts while making three kinds of turn maneuvers (straight through, left turn, and right turn) under day and nighttime conditions. Three important findings were evident. First, the results show that the position of the vehicle within the roundabout (approach, entry, and exit) had a significant impact on drivers’ visual behavior toward pedestrians. Drivers looked at pedestrians longer when they (drivers) were at the approach portion of the roundabout and less at the entry and exit portions of the roundabout. Second, the number of lanes at the roundabout did not significantly affect the drivers’ fixation durations toward the pedestrians. Finally, the age of the drivers and time of day did not significantly influence fixation durations toward the pedestrians at the roundabouts.
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    The Refinement of Drivers Visibility Needs During Wet Night Conditions: Wet Visibility Project Phase III
    Gibbons, Ronald B.; Williams, Brian M. (Virginia Center for Transportation Innovation and Research, 2011-06)
    The purpose of this project was to develop a specification for the minimum retroreflectivity of pavement markings in wet nighttime conditions. In order to establish this specification, the performance of four retroreflective pavement marking materials in wet-night conditions was evaluated. The performance of the pavement markings was evaluated by driver participants under simulated rain conditions using a similar protocol to studies that have already been performed at the Virginia Tech Transportation Institute. The performance of the markings was verified based on the participants ability to detect the end points of the markings in both rainy and clear conditions. The conclusions from this investigation indicate the following: The materials developed over recent years show an improved performance over those tested previously. These materials provide adequate performance through improved technology and performance. The log-linear relationship found previously is functional for the data provided. Two models were developed. The model with no intercept provides a more constrictive boundary at low levels of retroreflectivity. A retroreflectivity value above 250 mcd/m2/lx provides limited return in terms of detection distance. A specification limit of 150 mcd/m2/lx will provide adequate visibility for 55 mph in dry conditions and 40 mph in wet conditions using standard dry retroreflectivity measurements, and 1 in/hr measurements for the wet conditions. This value should be the minimum maintained over the life of the marking. The retroreflectivity specification for a white and a yellow material should be equal. The rumble stripe showed a significant recovery time improvement over the other tested materials. This study recommends a minimum retroreflectivity of 150 mcd/m2/lx for white and yellow pavement markings in both dry and wet nighttime conditions. This level provides the Virginia Department of Transportation with the basis for establishing a performance-based specification for pavement markings
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    Splash and Spray Assessment Tool Development Program: Final Report
    Flintsch, Gerardo W.; Tang, Lijie; Katicha, Samer W.; de León Izeppi, Edgar; Viner, Helen; Dunford, Alan; Nesnas, Kamal; Coyle, Fiona; Sanders, Peter; Gibbons, Ronald B.; Williams, Brian M.; Hargreaves, David; Parry, Tony; McGhee, Kevin K.; Larson, Roger M.; Smith, Kelly L. (Virginia Tech. Virginia Tech Transportation Institute, 2014-10-07)
    The effects of vehicle splash and spray are well known to motorists who have driven in wet weather conditions. Research suggests that splash and spray contribute to a small but measurable portion of road traffic accidents and are the source of considerable nuisance to motorists. Splash and spray from highway pavements also can carry a number of pollutants and contaminants. When deposited, these contaminants can be poisonous to plant life and accelerate the corrosion of roadway appurtenances. Splash and spray are individually definable processes that are the product of a number of different factors. Many parties have gone to great lengths to reduce the splash and spray created by motor vehicles, especially that from heavy vehicles, by retrofitting devices that alter the vehicle’s aerodynamics. Another possible solution to the problem is to change the characteristics of the highway pavement. Previous research shows that pavement geometry, drainage, texture, and porosity all contribute to splash and spray generation, but the exact mechanisms are largely unknown. A model capable of predicting the splash and spray propensity of pavements can be used by highway engineers to support decisions in highway maintenance and design. The project objective was to develop a simple and practical assessment tool to characterize the propensity of highway sections to generate splash and spray during rainfall and the impact of splash and spray on road users. This report summarizes the development of the splash and spray model and its implementation in an easy-to-use, practical tool.
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    Virtual Reality as a Tool to Evaluate Pedestrian Safety
    Bhagavathula, Rajaram; Williams, Brian M.; Owens, Justin M.; Gibbons, Ronald B. (National Surface Transportation Safety Center for Excellence, 2020-06-25)
    Virtual reality (VR) promises to be an effective tool to evaluate changes to the built environment that could improve safety for pedestrians. However, in order to draw actionable conclusions from VR, it is important to understand the degree to which pedestrians’ perceptions and behaviors match across real and virtual environments. In this study, participants experienced equivalent real and virtual environments and performed similar tasks in each. Tasks included the intention to cross an intersection, the estimation of the speed and distance of an approaching vehicle, and the perceived safety and risk of crossing a road. Results showed no statistical difference between the real and virtual environments for participants’ intention to cross, estimation of distances, and perceptions of safety and risk. Statistically significant differences between real and virtual environments were observed in the estimation of speed and measures of presence. These results indicate that at lower vehicle speeds (25 mph and lower) VR can be used as tool to evaluate pedestrian safety in built environments.