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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.

Retroreflective traffic markings are frequently used on roadways to provide guidance to drivers as supplements to regular markings. Portable retroreflectometers are widely used to measure the photometric characteristic of retroreflective traffic markings at present. Portable retroreflectometers include an internal light source and photoreceptors. It is based on the substitution method. Substitution relies on the use of calibrated reference plate. The traffic marking has a low coefficient of retroreflected luminance. It is difficult to measure the coefficient by direct measurement method. The direct measurement method cannot assign measurement values to the reference plates. The paper proposes a new measurement method to solve the problem of measuring the photometric characteristic of the retroreflective traffic marking. It is called the expanded direct luminous intensity method, and it is different from the four methods in JT/T 690 Test Method for Photometric Characteristics of Retroreflectors. The expanded direct luminous intensity method based on CIE angular reference system. A calibrated standard source A illuminates the specimen at a distance of 15 m from the specimen. And a calibrated low-light illuminometer is used to measure the retroreflectivity of the specimen. The paper built a standard system according to this method. The measurement uncertainty of the system is 3.1% while k is 2. After comparing with several different kinds of portable retroreflectometers, the results were satisfactory. Studies have shown that this method and standard system can not only calibrate the reference plates, but also measure the photometric characteristic of retroreflective traffic markings specimens.

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.