A controller for providing user input of a desired direction of motion or orientation for a transporter. The controller has an input for receiving specification by a user of a value based on a detected body orientation of the user. User-specified input may be conveyed by the user using any of a large variety of input modalities, including: ultrasonic body position sensing; foot force sensing; handlebar lean; active handlebar; mechanical sensing of body position; and linear slide directional input. An apparatus that may include an active handlebar is provided for prompting a rider to be positioned on a vehicle in such a manner as to reduce lateral instability due to lateral acceleration of the vehicle.