Ship’s (voyage) time
Time at sea and time in port Tough competition in the last couple of decades has caused container shipping, in particular, to be able to achieve profit only through economies of scale. This has led to larger ships and ever shorter cargo handling times and demurrage. Today, new potential for economisation can only be achieved by reducing operating and fuel costs. Two ways out of this predicament are either to use "slow steaming", meaning a ship's speed is reduced to save fuel, or to deploy even bigger ships, allowing the higher fuel costs to be spread over the additional tonnage. However, increasingly strict environmental requirements in harbours and en route limit the engine size and thus the size of the ships. When it comes to the operation of container shipping lines, the timetables of the routes are normally fixed. If the ships are delayed in port at some points, they are forced to make up for the lost time by increasing their speeds at sea.