Nearly a million journeys have been made by passengers between Truro and Falmouth since the train service was doubled two years ago.
An estimated 945,000 journeys have been made on the Maritime Line since the improved service was introduced in May 2009. It compares to 579,081 made in the previous two years.
Work on the line included rebuilding Penryn station, and creating a passing loop, which allows trains to now run every 30 minutes.
The work, costing £7.8 million, was funded by the European Regional Development Fund, Cornwall Council and Network Rail.
Cornwall Council Cabinet member for Transportation and Highways, Graeme Hicks said: "This has been a huge success for rail passengers that has attracted hundreds of thousands of passengers.
"We need good transport links in Cornwall and working with our partners we are very pleased to have achieved that.
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