Retroreflection Research Papers - Academia.edu (original) (raw)

—Indoor localization is very important to enable Internet-of-things (IoT) applications. Visible light communication (VLC)-based indoor localization approaches embrace many advantages, such as utilization of existing ubiquitous lighting... more

—Indoor localization is very important to enable Internet-of-things (IoT) applications. Visible light communication (VLC)-based indoor localization approaches embrace many advantages, such as utilization of existing ubiquitous lighting infrastructure, high location and orientation accuracy, and no interruption to RF-based devices. However, existing VLC-based localization methods lack a real-time backward channel from the device to landmarks and necessitate computation at the device, which make them unsuitable for real-time tracking of small IoT devices. In this paper, we propose and prototype a retroreflector-based visible light localization system RETRO, that establishes an almost zero-delay backward channel using a retroreflector to reflect light back to its source. RETRO locates passive IoT devices without requiring computation and heavy sensing (e.g. camera) at the devices. Multiple photodiodes (i.e. landmarks) are mounted on any single unmodified light source to sense the retroreflected optical signal (i.e. location signature). We theoretically derive a closed-form expression for the reflected optical power related to the location and orientation of the retroreflector, and validate the theory by experiments. The characterization of received optical power is applied to a received signal strength indicator (RSSI) and trilateration based localization algorithm. Extensive experiments demonstrate centimeter-level location accuracy and single-digit angular error.

Motor vehicle crash fatalities involving pedestrians result in 1.8 deaths per 100,000 population annually in the US. Most of these fatalities are attributed to the pedestrian not being seen in time for the driver to avoid a collision,... more

Motor vehicle crash fatalities involving pedestrians result in 1.8 deaths per 100,000 population annually in the US. Most of these fatalities are attributed to the pedestrian not being seen in time for the driver to avoid a collision, particularly under poor lighting conditions. Previous research shows that reflective clothing worn at night significantly increases a pedestrian's visual conspicuity to drivers, especially when worn on a part of the body that moves. The purpose of the present research was to examine pedestrians' willingness to pay an additional dollar amount for clothing providing increased conspicuity at night. Two studies were conducted with sample sizes of n = 340 and 325, respectively, comprised of university students and non-students. Findings from these two studies suggest that over 49 percent of respondents would be willing to pay an additional amount ($33 versus $30) for a sweat shirt or jacket, and over 60 percent would pay the same additional amount for athletic shoes. These findings suggest that a relatively large segment of the population are interested in and would be willing to spend more for clothing with reflective material. In both studies, significantly more women than men selected the reflective material option. Respondents spending more time outdoors at dusk or at night walking, running or jogging professed a significantly greater willingness to purchase the reflective clothing than respondents reporting spending less time outdoors at dusk or after dark. Implications for product marketing and future research are discussed.

Retro-reflective coatings applied to blinds of reduced geometric complexity promise to provide view to the outside while effectively controlling solar gains and glare. To characterize the reflection characteristics of such coatings over... more

Retro-reflective coatings applied to blinds of reduced geometric complexity promise to provide view to the outside while effectively controlling solar gains and glare. To characterize the reflection characteristics of such coatings over the entire solar spectrum, a novel extension to a scanning gonio-photometer is developed. The extended instrument is tested and applied to measure a coating's Bidirectional Reflection Distribution Function including the region of the retro-reflected peak. The measured data-sets are compiled into a data-driven reflection model for the daylight simulation software Radiance. This model is applied to illustrate the coating's effect in a comparison to purely diffuse and specular surface finishes on geometrically identical, flat blinds. Daylight supply, the probability of glare, and solar gains are assessed for an exemplary, South-oriented office under sunny sky conditions. The results indicate the potential of the coating to effectively shade direct sun-light even if applied on blinds with minimalistic geometries. The modeling technique is shown to be a general means to replicate the irregular optical properties of the coating, which cannot be represented by the standard models in daylight simulation software.

ABSTRACT The innovative time series methodology that is presented was used to examine the relationship between the safety impact of longitudinal pavement markings and their retroreflectivity. The need for the methodology was determined... more

ABSTRACT The innovative time series methodology that is presented was used to examine the relationship between the safety impact of longitudinal pavement markings and their retroreflectivity. The need for the methodology was determined through an examination of the pavement marking safety literature, the desire to build on previous retroreflectivity research, and an understanding of how retroreflectivity is a function of the age of pavement markings and markers. The time series methodology involves solving for multipliers that represent the change in the expected number of crashes as a function of pavement marking retroreflectivity while simultaneously solving for seasonal effect multipliers. The time series methodology is explained in detail; its usefulness has been demonstrated through the analysis of 8 years of pavement marking and marker installation data, traffic volumes, and crash data. Safety effect multipliers were solved for yellow and white pavement markings separately and in combination. The multipliers covered different road types and crash severities by using retroreflectivity models and California's data for more than 118,000 nonintersection, nondaylight (night, dawn, and dusk) recorded crashes. To apply the time series methodology, it was necessary to develop retroreflectivity models as a function of age, color, marking material type or marker type, climate region, and amount of snow removal. The results showed that retroreflectivity levels have no effect to a small effect on the safety performance of those roadways maintained to a reasonable level of pavement marking.

Motor vehicle crashes involving pedestrians result in 1.8 deaths per 100,000 population annually in the U.S. Most of these fatalities are attributed to pedestrians not being seen in time for the driver to avoid a collision, particularly... more

Motor vehicle crashes involving pedestrians result in 1.8 deaths per 100,000 population annually in the U.S. Most of these fatalities are attributed to pedestrians not being seen in time for the driver to avoid a collision, particularly under poor visibility conditions. Previous research shows that reflective clothing worn at night can substantially increase pedestrians' visual conspicuity to drivers. The purpose of the present research was to examine people's desire for reflective trim on their clothing. Findings of strong desirability for reflective trim could prompt its incorporation into garments available to the public, and thus, potentially decrease pedestrian-related motor vehicle accidents. The present study measured the extent to which people are willing to pay extra or less for clothing with reflective material compared to the same items without reflective material. People reported they are willing to pay more for reflective material on sports-related, children's and inclement-weather clothing. Implications for safety and future research are discussed.

Motor vehicle crash fatalities involving pedestrians result in 1.8 deaths per 100,000 population annually in the US. Most of these fatalities are attributed to the pedestrian not being seen in time for the driver to avoid a collision,... more

Motor vehicle crash fatalities involving pedestrians result in 1.8 deaths per 100,000 population annually in the US. Most of these fatalities are attributed to the pedestrian not being seen in time for the driver to avoid a collision, particularly under poor lighting conditions. Previous research shows that reflective clothing worn at night significantly increases a pedestrian's visual conspicuity to drivers, especially when worn on a part of the body that moves. The purpose of the present research was to examine pedestrians' willingness to pay an additional dollar amount for clothing providing increased conspicuity at night. Two studies were conducted with sample sizes of n = 340 and 325, respectively, comprised of university students and non-students. Findings from these two studies suggest that over 49 percent of respondents would be willing to pay an additional amount ($33 versus $30) for a sweat shirt or jacket, and over 60 percent would pay the same additional amount for athletic shoes. These findings suggest that a relatively large segment of the population are interested in and would be willing to spend more for clothing with reflective material. In both studies, significantly more women than men selected the reflective material option. Respondents spending more time outdoors at dusk or at night walking, running or jogging professed a significantly greater willingness to purchase the reflective clothing than respondents reporting spending less time outdoors at dusk or after dark. Implications for product marketing and future research are discussed.