# A Methodological Approach to the Study of Retroreflective Pavements
## 1 Introduction  
One of the main challenges facing the current society is climate change [1]. This phenomenon is demonstrated by the increase in global temperature, which has a significant impact on the environment and society in general [2, 3]. According to the Intergovernmental Panel on Climate Change (IPCC) [4], the Earth's average surface temperature has increased by approximately 1.2 \({}^{\circ}\)C since the late 19 th century, primarily driven by human activities such as the burning of fossil fuels and deforestation. Moreover, the IPCC predicts that the global temperature rise is likely to reach or exceed 1.5 \({}^{\circ}\)C between 2021 and 2040, with a 50% probability. The temperature increase is even more pronounced in urban areas due to the phenomenon known as the urban heat island effect [5, 6], with temperature differences between urban and rural areas observed to range from 1 to 14 \({}^{\circ}\)C [7, 8, 9]. This effect is intensified by several factors. High heat emissions result from concentrated human activity. Additionally, lower levels of vegetation and a high concentration of materials such as asphalt mixtures, concrete, and bricks contribute to this effect. These materials absorb solar radiation, causing their temperatures to rise [10, 11]. They are characterised by a high thermal storage capacity and low solar reflectance. As a consequence, their surface temperature increases during the day and releases the absorbed heat at night, keeping temperatures high. This phenomenon not only increases energy demand for cooling but also raises mortality due to heat stress, exacerbated during heat waves, which will be more intense and frequent as a consequence of climate change [12; 13; 14]. Tackling the urban heat island effect problem is essential for improving the habitability and sustainability of cities in the context of global climate change. The urban heat island effect is strongly influenced by streets paved with asphalt mixtures, which comprise approximately 29% to 39% of the urban surface area [15]. These dark pavements have a high capacity for solar radiation absorption due to their low albedo, which means they reflect little sunlight while retaining and re-emitting substantial heat [16]. According to [17], pavements absorb between 80% and 95% of incident solar energy. Thus, in the middle of summer, the surface temperature of bituminous pavements can exceed 70 \({}^{\circ}\)C, heating the local air [18; 19]. Mitigating the impact of the heat island effect requires the implementation of new technological solutions that maintain lower surface temperatures on streets and pavements, such as cool pavements [20; 21]. Within the different cool pavement technologies developed to date, reflective pavements can significantly contribute to reducing the urban heat island effect. These are characterised by high solar reflectance, defined as the fraction of incident solar radiation that is reflected. This property means reflective pavements store less heat, thereby maintaining a lower surface temperature compared to conventional pavements. Moreover, they can improve night-time visibility, reducing the need for artificial lighting. The literature contains various studies on the development of reflective pavements. [PERSON] et al. [22] conclude that increasing the albedo of the pavement by 0.1 reduces its average temperature by 2.1 \({}^{\circ}\)C. Research on reflective pavements has mainly focused on new chip seals and coatings. [PERSON] et al. [23] used the construction and demolition waste of different colours as aggregates to manufacture different chip seals with the aim of reducing the heat island effect. In their study, a spectrometer with sensitivity in ultra-violet, visible, and near-infrared spectral regions was used to determine the reflectance of the chip seals, finding that the red brick chip seal reflected the most solar radiation and released the least heat at night. [PERSON] et al. [24] modified an asphalt binder with TiO\({}_{2}\) quantum dots, increasing the solar reflectance by up to 12%.