# Application of Data Mining Techniques to Predict Luminance of Pavement Aggregate
## 1 Introduction  
According to the nomenclature used in European countries, light-colored pavements are those that use light-colored aggregates and synthetic binders that are either colorless or light-colored using the corresponding pigment. Lightened pavements, on the other hand, are those that use traditional asphalt as a binder, while the aggregates are of the light-colored group. Light-colored pavements are defined as pavements whose wearing course visually gives the impression of a light-colored pavement. Invariably in these type of solutions, the important element is the aggregate itself [1]. In 1982, the Commission Internationale de l'Eclairage (CIE) [2] introduced the concept of luminance to evaluate pavement brightness. Following this, a number of methods have emerged for evaluating this parameter. Nevertheless, the evaluation of this criterion is complex and still requires an improvement of measurement methods [3]. CIE introduced the R classification system according to which each type of pavement is classified into one of four classes, from R1 to R4. Each of the four classes has a defined reflectance table (r-table) containing the reduced luminance coefficient [4]. Unfortunately, the R classification is based on measurements from 1960 to 1970, and it should be taken into account that there have been changes in asphalt pavement technology (mma) and requirements for macro-texture, in addition to the introduction of new grain sizes of mineral mixtures and types of asphalt binders [5, 6]. The purpose of road brightening, assessed through luminance coefficient q, is to cause structures and traffic participants on them to be visible, minimizing driver discomfort. According to the authors of [7], pavement brightening results in an approximately 30% reduction in road accidents. It should be kept in mind that another very important part of road brightening is the reduction in the amount of energy required for adequate visibility at night. In this aspect, approx. 1.3% of the energy consumed in the EU is used by road lighting [8]. However, there are still questions of what to focus on when brightening the pavement. Reflection from the road surface is a function of the physical condition of the road and its nature, as well as the direction of illumination and viewing conditions [5]. Different pavements can have different reflection characteristics, which depend on the texture of the pavement, its age, the paving materials, the bonding materials, and the paving methods. The reflection characteristics change with weather conditions and the physical condition (for example, when bumps or cracks appear). As the reflective properties of road pavements change, so does their luminance [9]. Luminance is closely related to the type of aggregate. Light aggregates such as: granite, gabbro, and quartzite, in contrast to limestone, are extracted from acidic rocks with high SiO\({}_{2}\) content. Therefore, these are aggregates with a low asphalt affinity. The macro-texture of most light rocks reflects light in a diffuse rather than a directional manner, minimizing driver glare exposure. In addition, light-colored rocks such as quartzite, granite, and gabbro, in contrast to sedimentary rocks, have a high roughness coefficient, enabling an increase in the roughness of the pavement [1]. Therefore, there are some contradictions between the luminance of the aggregate and its applicability. Nowadays, it is much more common for pavement materials to be dark-colored and the standard r-table does not reflect their reflective properties [10]. Consequently, more energy is required to illuminate the road surface. Despite the fact that the type of material in the pavement affects its luminance, the phenomenon of light reflection is not directly taken into account during the design [11]. In the European Union, the design of road lighting is subject to regulation with some derogations to the member states.