The paper presents a comprehensive analysis on reclaimed asphalt pavement (RAP) milling material collected from a single source, namely from a secondary road in Romania, county road DJ109. The following characteristics are investigated: particle size, binder content, material variability and uniformity, and the clustering phenomena. Variability is demonstrated using the results of particle size gradation and binder content. The coefficient of uniformity and the coefficient of curvature demonstrate that the RAP used in this research is a well-graded material. However, the visual analyses conducted on RAP highlight the presence of RAP particle agglomeration and the need for further testing. The study presents three different experimental phases: (i) RAP-milling old asphalt pavement, RAP; (ii) RAP milling after binder extraction, RAPabe; and (iii) RAP after Los Angeles crushing, RAPac. After processing, the coarse part (C) had a great influence on the fine part (F), and F/C ratio increased, respectively, from 0.4 to 1.5 and 1.61. Material variability on the extended site, the difference between the design values and particle size, as well as the existing clustering process indicated that RAP material collected from secondary roads must be pre-processed prior to its storage and reuse in the recycling process. Considering that secondary roads represent 71% of the overall network of asphalt course roads in Romania, and around 24,000 km of roads are in need of at least extensive maintenance (wearing asphalt courses) or rehabilitation, RAP is a highly recyclable material. Therefore, this study provides advice and guidance for re-using RAP in new pavement mixtures.

Pollution is closely related to traffic characteristics (vehicle fleet, its composition in terms of motorization, park maintenance level, etc.), existing road infrastructure (depending on the classification of public roads into technical classes, the level of service) and last but not least, the speed of traffic on the public road network (depending on the designed geometric elements, local context, geographical position and climate). Determining optimal traffic speeds in order to reduce pollution is a highly debated topic for all categories of public roads, including highways, which by definition are designed and executed with distinct geometric elements to ensure high-speed road traffic. When adopting the geometric elements, the design speed adopted in accordance with the legislation in force, plays an essential and decisive role both in the design of new roads and in the rehabilitation of existing ones. The comparative study of the maximum design speeds (imposed by regulations) with the optimal ones in terms of reducing air pollution (recommended by specialized studies), can provide new perspectives from the point of view of all traffic participants by correlating the optimal average speeds with the designed geometric elements.