More proactively, and competitively, in the context of ship construction and technology, some ships are more environmentally
friendly than others by design, as measured by the Energy Efficiency Design Index (EEDI). Newer ships tend to
be more energy efficient than older ones as hull and engine designs improve with time, and engines lose efficiency with
age and use. Some ports have considered including the EEDI in the determination of port fees, to encourage more energy
efficient shipping. Shipping lines now commonly optimize routes with respect to weather and currents to save fuel. Likewise
ballast and trim can be optimized to save fuel.2