A control system for a ground working vehicle. The control system may include a handle assembly including a handle member extending upwardly and rearwardly from a chassis of the vehicle. The control system may also include a speed control apparatus including a control grip operably connected to, and translatable along, the handle member. Translation of the control grip may activate a transmission to move the chassis in the forward direction when the control grip is translated downwardly along the handle member towards the chassis. Further, the control system may include a lockout apparatus movably attached to a handle member. The lockout apparatus may be adapted to selectively and physically restrict movement of the control grip relative to the handle member.