# Asphal Road Pavements to Address Climate Change Challenges--An Overview
## 4 Solutions for Mitigating Climate Change Challenges
### Pavement Solutions  
#### 4.2.1 Permeable Pavements  
Permeable pavements are a pavement solution that can help flood management. The water can percolate into the pavement layers, reducing thus surface water height. It is also a generic term; permeable pavements include but are not limited to porous asphalt, pervious concrete, and paver blocks. Porous asphalt is a mixture with a high air voids content, so the water drains through the asphalt surface layer [66] (Figure 3). Therefore, it increases safety by decreasing hydroplaning and splashing. In addition, as porous asphalt presents an open-grade surface, it increases skid resistance and reduces traffic noise. In fact, asphalt pavement surface characteristics, such as macrotexture, influence road safety [47]. Permeable pavements also benefits the ecological environment (promotes groundwater resources recharging) [66; 67; 68]. Despite the advantages, serious issues affect its performance and pavement life. Void structure clogging is one of them [69]. The water drainage through the mixture voids and traffic makes some particles (dust, tyre wear particles, etc.) accumulate in the mixture voids, changing the pavement permeability and durability. Several researchers have been studying this issue. [PERSON], [PERSON], [PERSON], [PERSON], [PERSON], and [PERSON] [69] analysed, at the microscopic level, the water drainage through the porous asphalt with the seepage depth, velocity, and path. They concluded that the results depend on clogging size particles and mixture voids content. [PERSON] et al. [57] explored the permeability variation in the clogging process, considering the water head height, the mixture gradation and the clogging particles. They concluded that the effect of clogging on the permeability varied with direction. The clogging effect on the transverse permeability was noticeably more remarkable than on the vertical permeability. Again, it depends on the water head height, mixture gradation, and clogging particles. Another issue is the mixture's durability [66; 68; 70]; porous asphalt is more exposed to climatic actions and, consequently, is more prone to ageing. [PERSON], et al. [71] studied the effect of air voids content (16.2, 20.7 and 23.8%), modifier am  
Figure 3: Permeable vs conventional pavements. ageing (short- and long-term). and test temperature (0, \(-\)10 and \(-\)20 \({}^{\circ}\)C) on porous asphalt performance, concluding that the most critical factor was the modifier amount. Next was the test temperature. The effect of air voids content and ageing were not as significant. To improve porous mixture durability, modified bitumen is currently used. [PERSON], [PERSON], [PERSON], [PERSON], [PERSON], [PERSON], and [PERSON] [66] present a comprehensive review of this kind of mixture, helping to understand the context better. It is also essential to assess the effectiveness of permeable pavements in flood management. [PERSON], et al. [72] compared four permeable pavement structures in terms of infiltration using artificial rainfalls and full-size pavements. They concluded that thicker structures with reasonable combined air voids perform better. [PERSON], et al. [73] used numerical simulations to assess the effectiveness of four permeable solutions against different rainfall events. All solutions perform better than a conventional impervious pavement. The worst-performing one was the porous asphalt over an impermeable layer. [PERSON] et al. [74] measured the monthly infiltration rates of two permeable solutions (porous asphalt and porous concrete blocks) and monitored 36 rainfall events. They found a runoff peak reduction from 16% to 55%, depending on rainfall intensity; an average reduction in the rainfall volume of 37.6%; and an infiltration rate decrease over the 15 measured months. The infiltration rate decrease depends on the location. In the porous asphalt solution, the rate remains high at one location and decreases inconsistently in other locations.