In light of requirements that rubber be mixed with any asphalt used in projects receiving federal aid beginning in 1994, and the general increase in the problem
TRB's National Cooperative Highway Research Program (NCHRP) Report 752: Improved Mix Design, Evaluation, and Materials Management Practices for Hot Mix Asphalt
Modern highway engineering reflects an integrated view of a road system's entire lifecycle, including any potential environmental impacts, and seeks to develop