Port freight traffic statistics are based on a combination of data reported to the DfT by port authorities and shipping lines or their agents.
Mae ystadegau traffig cludo nwyddau porthladdoedd yn seiliedig ar gyfuniad o ddata a roddir i'r Adran Drafnidiaeth gan awdurdodau porthladdoedd a chwmnïau llongau neu eu hasiantau.