This chapter contains a laboratory assessment of the role of geosynthetics in the performance of railway ballast. The main objectives of this testing were to examine the actual potential of selected geosynthetic products for ballast stabilisation. A series of cyclic drained tests were carried out using a large scale prismoidal triaxial apparatus that was designed and built at the University of Wollongong, and is the most innovative cyclic process simulation testing equipment available in the world today. The effects of different types of geosynthetics, including bi-axial geogrid, non-woven geotextile and geocomposite (a combination of bi-axial geogrid and non-woven geotextile) have been evaluated as single layer and dual layer arrangements. The test findings revealed that bi-axial geogrid with aperture size of 40 40 mm and with minimum bi-directional strength that complies with the University of Wollongong recommendations, would be a suitable grid reinforcement to be placed under the ballast layer for track stabilisation. This particular non-woven geotextile offered an optimum separation function between the ballast and capping layers and maintained a higher resiliency during cyclic loading. Among the three types of geosynthetics tested, the use of geocomposite resulted in the least strain and particle breakage. The dual layer configuration reduced deformation and degradation better than the single layer configuration.