沙子和防冻剂的混合物，用于在极端天气下辅助牵引力。沙尘暴S4还包含钢丸，以协助An electrical circuit that includes an insulated section of track. A train occupying the track will complete the circuit by connecting the two rails together via its wheels and axles thus signaling the trains occupation of that section of track. Track circuits are designed to detect the presence or absence of a train.
" class="glossaryLink ">轨道电路操作
