Lateral restraint and stability are essential factors in preventing the buckling of railway tracks, especially as a result of the tendency of the rails to expand in hot weather. Many factors influence lateral restraint including sleeper type, weight, contact area between the sleeper and ballast, sleeper spacing, ballast grading and density, and the dimensions/geometry of any ballast shoulder. Additional stabilising measures sometimes provided to increase lateral stability include under-sleeper pads (USPs) and lateral restraint plates (LRPs). This paper presents the results of a series of experimental studies into the effects of these measures on different sleepers using the Southampton Railway Testing Facility (SRTF). The results show that attaching USP and LRP to a standard concrete sleeper increases the lateral resistance by about 50% and 47.46%, respectively. For other types, the weight of the sleeper influences the percentage increase/decrease in the lateral resistance.