IT’S all aboard in Southampton as the city prepares to welcome nine of the world’s most famous cruise ships to the port this weekend.

In what promises to be Southampton’s busiest 48 hours of the year the arrival and departure of so many vessels is expected to bring an extra 12,000 vehicles on to the city’s roads.

So it’s … All Aboard: In excess of 45,500 passengers, more than the total population living in the city of Salisbury, will cross the city’s dockside as they embark and disembark the ships.

All Aboard: Bus journeys, beginning and ending within Southampton’s boundaries, will be free over the weekend in an attempt to cut down the number of cars on the roads and ease congestion.

All Aboard: Free “Do the Docks’’ bus tours will operate on both Saturday and Sunday on a first-come, first-served basis and will last approximately 75 minutes. Buses will depart from Ocean Village at 10am, 11.30am, 1pm, 2.30pm and 4pm.

In port tomorrow will be Royal Caribbean International’s Independence of the Seas, P&O Cruises’ Oceana, Fred Olsen Cruise Lines’ Black Watch and Cunard’s flagship, RMS Queen Mary 2.

Black Watch is due to depart at 4.30pm while the other ships are scheduled to leave about 30 minutes later.

Sunday sees the arrival of a further three P&O Cruises vessels, Oriana, the superliner, Ventura and Aurora together with Cunard’s Queen Victoria.

Ventura and Queen Victoria are timed to sail at 5pm while Oriana and Aurora should leave about one hour later.

Southampton City Council has teamed up with bus companies Bluestar, First and Unilink as well as Black Velvet to provide free bus travel until 6pm tomorrow and Sunday.

Sightseers will have the best views of the ships from Mayflower Park, Town Quay, Hythe Marina and Calshot.