text: The term is typically used to refer to rail systems with rapid transit-style features that usually use electric rail cars operating mostly in private rights-of-way separated from other traffic but sometimes , if necessary , mixed with other traffic in city streets .
simplified: The term is normally used to refer to rail systems with rapid transit-style features that usually use electric rail cars operating mostly in private rights-of-way separated from other traffic but sometimes , if necessary , mixed with other traffic in city streets .