Once this threshold was overcome, the size of containerships entering service quickly increased. In about a decade containership design went from a maximum capacity of 6,700 TEU to 14,500 TEU. Design constraints are now limited by the capacity of port channels to accommodate containership drafts and as well as the availability of cranes large enough to unload them. In addition, they cause additional pressure on inland transport systems to accommodate the large volume of containers they can transship. Speed-wise, a threshold of about 25 knots has been reached as energy consumption would forbid higher operational speeds.