This project demonstrated that open-graded, permeable, subbase materials can be designed that provide adequate constructibility and pavement support as well as good internal drainage at a competitive cost. Five types of subbases ranging from an impermeable cement stabilized material to a very permeable, uniformly graded, crushed aggregate were evaluated during this 7-yr research project. Testing indicated that the open-graded subbases had adequately high permeabilities, but the dense-graded subbase permeability was unsatisfactorily low. Deflection measurements, indicating the relative strength of the pavement structure in each subbase section, were made using a falling weight deflectometer. The lowest pavement deflections were found in the aggregate cement section. Deflections in the asphalt treated permeable material (PA No. 2B aggregate) and high permeability aggregate sections were approximately equal to each other and slightly higher than those measured in the aggregate cement section. The highest deflections were measured in the PA No. 2A aggregate section. The results of this evaluation infer that dowel looseness, pavement temperature, loading magnitude, and the extent of beam-like behavior exhibited by underlying subbases all influence joint efficiency measurements. Joint efficiency appears not to be controlled by one or even a few factors at a particular site but is influenced by a combination of factors in the pavement structure and environment during testing. Roughness measurements showed smooth pavementns can be built on all five subbase types. After 7 yr, no significant difference in riding characteristics exists among the five subbase sections.