Road traffic markings are made of glass beads embedded in paint. To analyze the effects of glass-bead radius, embedment depth, correlated color temperature of light sources, and incident angle on the reflective performance of glass beads, a numerical model is established using the geometric optics method, effective light conditions are analyzed, calculation methods for optical power devised, and non-standard planes of incident light calculated. Calculations were also carried out. Results show that the retroreflective properties of glass beads are positively correlated with the correlated color temperature of the light source and radius of the beads. The glass-bead radii, embedment depths, and incident angles have little effect on their reflective performance. Moreover, the correlated color temperature of the light source is an important factor affecting the accuracy of measuring glass-bead reflective performance. When using retro reflectometers, standard retro reflectance-measuring devices for retro reflectance measurement, and other equipment to evaluate the reflective performance of road traffic markings, the correlated color temperature of the light source of the equipment should be as close as possible to 2856 K.

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Large error exists in the photometric performance test of raised pavement marker. This paper reports a set of retroreflective measurement standard devices built to measure raised pavement markers based on the principle of direct measurement, and the photometric performance of the raised pavement markers was tested. The study also involved calibration of a portable meter using the standard device. According to the experimental comparison, the method proposed in this paper provides a new direction for the development of retroreflection measurement technology. The results measured by the proposed method showed high accuracy. This method can solve the large measurement error problems with indication errors of 2% at most.

Start your abstract here…The study aims to explore the technical specifications of the standard retroreflectivity measurement devices. Based on the measurement principle of retroreflection coefficient, the metrological characteristics of standard retroreflectivity measurement devices were proposed and the three main metrological indices of light source (color temperature, illuminance and positioning error of incident angle) were experimentally explored. The allowable error range of the retroreflection coefficient measurements was determined to calculate the corresponding ranges of metrological indices. With the entropy weight method, the weight of the influence of each index on retroreflection coefficient measurements was analyzed. The analysis results showed that the illuminance had the most significant influence on the retroreflection coefficient and accounted for 41.30%, followed by color temperature (34.43%) and angle change (24.26%). The study provides the important technical support for the development of technical specifications of standard retroreflectivity measurement devices.