第三軌条方式
Most interurban cars and freight locomotives collected current from an overhead trolley wire. The cars contacted this wire through the use of a trolley pole or a pantograph. Other designs collected current from a third rail. Some interurbans used both: in open country, the third rail was used and in town, a trolley pole was raised. An example of this was the Chicago, Aurora, and Elgin Railroad where a trolley pole was used in both Aurora and Elgin, Illinois. Third rail was cheaper to maintain and more conductive, but it was more expensive to construct initially and it did not eliminate the need for AC transformers, AC transmission lines, and AC/DC conversion systems. In addition, third rail posed a serious danger to trespassers and animals and was difficult to keep clear of ice.