A walk-behind self-propelled apparatus having a mobile structure and a handle assembly coupled to the mobile structure. The handle assembly includes a pair of grip portions. A ground engaging traction member is rotatably coupled to the mobile structure and imparts traction movement to the mobile structure for movement on the ground. A power source outputs drive power and a drive system, coupled between the power source and the ground engaging traction member, selectively transmits the drive power to the ground engaging traction member. A speed control actuation system is then coupled to the drive system and includes a control member pivotable about an axis. The axis is generally parallel to a plane extending between the pair of grip portions of the handle assembly to permit an operator to operate the control member merely through thumb actuation without removing their hands from the pair of grip portions.