In this paper we discuss the benefits of using rubber-modified asphalt concrete in high-speed railway foundations. We present the results from a series of three-dimensional finite element simulations modeling a high-speed train foundation utilizing various trackbed materials. Four trackbed materials were tested for their relative vibration attenuation capacities: ballast, concrete, conventional asphalt concrete, and rubber-modified asphalt concrete. Additionally, studies varying the speed and the weight of the passing train were performed. Parametric studies varying the dimensions of the trackbed underlayment were also examined. From these numerical simulations, it is shown that rubber-modified asphalt concrete outperforms other traditional paving materials in ground vibration attenuation. It is also shown that the speeds and weights of the passing trains and the dimensions of the trackbed have significant effects on the relative performance of the paving materials. Implications for design are discussed.