In many vehicles currently equipped with automatic transmissions, the decision of when to shift from a nondrive range to a drive range is made entirely by the operator of the vehicle. Vehicles equipped with a Park/Lock mechanism, block shifting from the Park range until the ignition switch is in the run position. There are no further constraints on shifting of these vehicles based on either the position of the accelerator pedal or the position of the brake pedal.
Prior art devices have been proposed to prevent shifting of a transmission until after the manipulation of an operator controlled mechanism. Two commonly suggested manipulations are the fastening of seat belts and the depressing of the service brake pedal. Prior art devices have also employed solenoids in preventing shifting.
Solenoids have been used to prevent shifting by moving restricting plates, linking and unlinking the shift lever from the rest of the shifter, blocking the motion of the shift linkage by inserting a pin in the linkage path, and engaging a pawl with a rack.