Take That Cardiff concert: Travel advice for fans
Extra train services are being laid on as Take That attract 60,000 fans to Cardiff's Millennium Stadium on both Tuesday and Wednesday.
Both Arriva and First Great Western are putting on more trains for the two performances.
Cardiff council is also warning concertgoers and city residents of road closures and likely congestion.
The group, who performed two gigs in Cardiff in 2009 as a four-piece, are now reunited with Robbie Williams.
Arriva Trains Wales said it was adding extra carriages to its valley services and Newport shuttle trains, warning that services would be busy in the build-up to the concerts starting at 1600 BST.
It said a queuing system would be in place at Cardiff Central station after each gig and that Queen Street station would be closed as usual after 2200 BST.
Simon Turton, special events manager for Arriva Trains Wales, said: "Due to the popularity of this event we advise passengers to leave additional time for their journey."
First Great Western will be running additional services to Swansea.
Cardiff council advises fans travelling to the city to plan their journeys well in advance, to arrive early, and use park and ride services from junction 33 of the M4 motorway if they are driving.
Westgate Street is to close at 1600 BST on Tuesday and Wednesday, with a larger road closure around the city centre in place from 2000 to 2230 BST.
The council added that all bus services travelling in and around the city would be affected.
Progress Live is said to be the UK's biggest pop tour with 27 stadium dates, and is the first time the original five members have toured together since 1995.
The stage production cost about £15m to put together, including a robot standing 30m (100ft) when fully upright.
Take That are due to perform to nearly 2m fans across Europe this summer.