This paper summarizes an extensive series of common durability, shape and strength tests carried out on road aggregates from quarries in northern Pakistan by Sharif et al. at the University of Engineering and Technology, Taxila. The data from these standard tests have been correlated for a particular aggregate type to show the close relationship between these measured physical characteristics. The paper outlines how, once these relationships have been established for a particular aggregate source, it is feasible to simplify the testing or quality assurance regime and monitor only some of these characteristics to assess the overall quality of the aggregate. The physical characteristics have then been combined into a linear relationship, using coefficients estimated from the extensive data set in the paper, to give a single characteristic for an aggregate type known as the Toughness Index (TI). The TI is therefore based on the main strength and durability characteristics of the aggregates and can be used as an indicator of the overall quality of the aggregate.