Abstract: A security/antitheft system in combination with a vehicular automated transmission system (10) is provided, requiring a minimum or no additional hardware. The security system includes logic rules for the transmission system controller (38) for preventing the controller from issuing the command output signals necessary for mobilizing the vehicle in the absence of operator-initiated enabling signals and, preferably, for interpreting a predetermined sequence of manipulations of the existing selector (1) as the required enabling signals.

Abstract: A method of, and apparatus for, retarding a vehicle equipped with an epicyclic gearbox in which a reverse gear train is included. In normal operation to engage reverse gear the reverse gear train contains a reaction member which is clamped to reverse the direction of rotation of the gearbox output shaft. To provide for retardation the reverse gear reaction member is not clamped but the clamping means is operated to allow slipping or intermittent operation of the reverse gear train so providing a retarded but not reversed operation of the output shaft.