most superficial muscle on the medial side of the thigh, being thin and flattened, broad above, narrow and tapering below

signal aspect which commands the train operator to leave the station or stop

advanced vehicle safety system that helps prevent collisions by sending the driver an acoustic or visual signal to warn of the presence of standing or slow-moving obstacles in the car's path, and which also acts on the car's brakes when necessary

interval or distance between two vehicles, trains, or ships traveling in the same direction along the same route