A mat comprising an elastic material which serves as an underlay for a ballast bed of crushed stone, metallic particles, or the like is provided with a plurality of projections on its underside and with an upper layer of a material different from the elastic material. This upper layer on the upper side of the mat advantageously comprises a strong fabric. Particularly the upper layer may comprise a multilayered fabric with inlay layers of elastic material positioned between the individual layers of the multilayer fabric as well as a coverying layer of a softer material on the upper surface of the upper layer of the mat. The fabric of the upper layer of the mat advantageously comprises a water and rot resistant plastic material, such as a polyamide.