Wessex Trains says the new trains will be in operation in February

The company is to add extra carriages to 10 of its trains serving the route which passes through Wiltshire and Bristol Temple Meads.

The move will mean the trains' seating will increase from 140 to 200.

Wessex Trains says the first services will be introduced during December with the rest in service by the end of February 2005.

Wessex Train's managing director, Alan Wilson, said: "Growing numbers of passengers are using this line and this has meant on occasions overcrowding has become a problem."