In Edinburgh, dozens of old catering carriages are being refurbished for use on trains from South Wales to London.
The planned expansion will add 84 extra standard class seats to the service which First Great Western says will help to alleviate overcrowding and make life more comfortable for people travelling to Paddington from Cardiff and Newport.
The train company has nine of the top ten most overcrowded trains. On some trains up to 300 people are forced to stand for their journey.
ITV Wales asked people waiting to go to Paddington from Cardiff's Central Station how they felt about the service.
While the watchdog welcomes the additional carriages, it says it will be the planned £5 billion upgrade of the Great Western mainline, and new fleet of trains, that will bring long-term relief to passengers - but that is some years off.
The trains are due to be upgraded in the next few weeks.