Motorists have been warned to expect extra traffic around Abergavenny and the Brecon Beacons this weekend because of the sold-out Green Man festival.
Singer-songwriter PJ Harvey headlines the 20,000-capacity festival at the Glanusk Estate in Crickhowell, Powys.
American band Future Islands headline the main Mountain Stage on Friday, Grammy-nominated Ryan Adams headlines on Saturday and PJ Harvey on Sunday.
A free shuttle bus service is being run from Abergavenny railway station.
A park and ride service is in operation to the site from Crickhowell and police have said traffic could be heavy on the A40 between Abergavenny and Brecon.
The A465 Heads of the Valleys road is also expected to be busier than normal as festival-goers head to the four-day event, where about 1,500 acts from music, comedy, literature and film will perform.
PJ Harvey, the first woman to win the Mercury Prize and the only person to have won it twice, has not played in Wales for more than 10 years and Green Man will be her only UK show in 2017.
Her headline set will be broadcast live on 6 Music on Sunday from 22:00 BST while Adam Walton will broadcast live from Green Man on BBC Radio Wales from 22:00 on Saturday.
This year's festival line-up also includes the two-time Mercury nominated Michael Kiwanuka, Lambchop, Conor Oberst, Angela Olsen and BBC Radio 6 Music's album of the year winners BadBadNotGood.
Event organisers have warned festival-goers fireworks, sound systems, glass bottles, open fires, tin foil barbecues, pets (except guide dogs) and weapons are not permitted on site - while alcohol is forbidden in its 17-stage entertainment area.
The festival was founded in 2003.