For a moment, let's return to the elevator example. While the addition of a gravity feedforward in the last section improves the position control, the PID controller is still doing the majority of the work to follow step responses. When a new position is commanded, the error immediately spikes and the controller saturates, sending the carriage at the mechanism's maximum acceleration. Soon the carriage slows down and overshoots the setpoint a little before settling around the commanded position. While efficient, the sudden acceleration causes unnecessary mechanical/electrical strain and the resultant overshoot wastes time. For drivetrain movements, there are additional issues with wheel slippage.