A special £15 day return ticket has been launched, to be used at weekends during the holiday month of August, by South West Trains.
SWT goes from London Waterloo to Portsmouth and Weymouth, as well as Dorset, Wiltshire, Hampshire and Buckinghamshire.
The Summer Fever tickets are valid for travel on Saturdays and Sundays between two SWT stations, with a few exceptions. Children travel for £7.50 and the tickets can be used any weekend from 3 August 2013 to 1 September 2013.
Travellers should beware, however, that the Warminster-Bristol Temple Meads line and the Exeter-Feniton line are excluded from the offer.
Isle of Wight Island Line trains are included, provided passengers hold tickets to Portsmouth Harbour.
"We hope it will encourage more people to give the train a try," said Arthur Pretorius of SWT.
Tickets can be bought in advance or on the day of travel at staffed stations, or from ticket vending machines in unstaffed stations.
Tickets can also be purchased in advance online or by phoning +44 (0)845 6000 650. The offer is valid on 3-4, 10-11, 17-18, 24-26 and 31 August and 1 September.
The Summer Fever ticket can be a big saving on some journeys. For example, a London to Weynouth off-peak day return, booked on the day of travel, normally costs £59.20.
More info: www.southwesttrains.co.uk/
Information from SWT