London Olympics 2012: Extra trains for Dorset sailing
Extra trains will run to Dorset during the Olympic Games.
The number of visitors in Weymouth and Portland on an average summer day is expected to rise from 30,000 to 100,000 during the sailing events, according to South West Trains.
The firm will provide 40% extra capacity at peak times. First Great Western will run three additional trains a day.
Team GB's Andrew Simpson said the area would be "thronged with sailing fans".
He added: "Team GB came top in the Beijing 2008 Olympic Sailing events, winning twice as many medals as our nearest rival - including four gold medals.
"It's going to be a fantastic party atmosphere but people need to plan their travel, not leave it to the last minute."
South West Trains said the area was a "travel hotspot".
"We have pulled out all the stops to put together a plan that maximises the capacity on the rail network to London and for the sailing events in Weymouth, within the infrastructure constraints we face," said a spokesman.
A First Great Western spokesman said the Olympic Delivery Authority predicted spectators could largely be "absorbed by our normal service" because of August having traditionally fewer commuters.
It is putting on additional services connecting Weymouth to the West Country, and will run two additional trains a day for the Paralympics.
The Olympic and Paralympic Sailing events take place between 29 July and 11 August, and 1 and 6 September.