Most modern diesel and electric locomotives can run equally well in either direction, and many are push-pull trains with control cabs at each end. In addition, railroads often use multiple locomotives to pull trains, and even with locomotives that have distinct front and rear ends, the engines at opposing ends of a locomotive "consist" (a group of locomotives coupled together and controlled as a single unit) can be aligned so they face opposite directions. With such a setup, trains needing to reverse direction can use a technique known as a "run around," in which the engines are uncoupled from the train, pull around it on an adjacent track or siding, and reattach at the other end. The engineer changes operating ends from the original locomotive to the one on the opposite end of the locomotive consist.