This paper describes a methodology for evaluating the asset condition of pavement foundations by principally non-intrusive methods. The methodology has been developed through a research program undertaken in the United Kingdom (UK). The methodology brings together various existing data sets, pavement performance data (in the form of TRACS data), and existing earthworks asset information data sources. The data is then coupled with non-destructive scanning undertaken by high speed ground penetrating radar (GPR). Combining these data sets enables an assessment to be made of likely sub-grade conditions, the route is then subdivided into a series of performance categories, and potential geotechnical problems can be identified. Bringing data sets together in this way by a standard methodology enables pavement foundation or subgrade performance issues to be understood and allowed for within pavement condition assessments. This will assist with the planning of intrusive ground investigation, and selection of appropriate maintenance works. This method offers potential benefits to the asset management of roads by reductions in engineering works program, cost, safety and traffic disruption.