Bus rapid transit systems have grown in popularity. Most existing and proposed BRT lines operate on city streets for all or a portion of their routes. They may run in mixed traffic; normal or contra-flow curb bus lanes, and/or arterial median busways. This paper describes the design, operations, and effectiveness of each; and identifies the key issues and tradeoffs. Drawing on ongoing research (TCRP Project A-23), it gives illustrative examples of usage, costs and benefits. It shows that with proper design, BRT can improve bus speeds, reliability and identity, while minimizing adverse impacts to street traffic, pedestrian and property access.