A pad for use in a rail mounting assembly to dampen the rail vibration while providing electrical insulation between a rail and a tie, particularly where positive retention of the pad against lateral slippage is accomplished independently of the means used to secure the rail to the tie. Retention against lateral slippage is provided by disposing embossments on the pad which mate into socket recesses in the tie. Wear, permanent set, and cracking are alleviated by disposing apertures through the embossments to interrupt the lateral propagation of the strain wave caused by compressive stress imposed on the rail mounting assembly from rolling train wheels. Dampening of rail vibration is supplemented by cooperatively configuring the embossments and the socket recesses to develop desired spring forces upon compression of the pad.