UK owner P&O Ferries has reported a 14% rise in freight volumes at its rail hubs of Zeebrugge and Europoort in the first six months.
It handled 42,421 units that were being shipped across the North Sea to the east coast of the UK.
Zeebrugge accounted for 30,154 units, with Europoort adding 12,087.
Last month, the ferry group said it had carried more freight across the English Channel in the first half than in any comparable period in its modern history.
Managing director Janette Bell said: "This outstanding performance at our terminals in Zeebrugge and Europoort illustrates that continental exporters are increasingly using our integrated rail and ferry service across the North Sea for reliable and punctual access to key markets in mainland Britain."
