Boxing fans going to the Anthony Joshua fight at Principality Stadium have been warned the last trains out of Cardiff could leave before the fight finishes.
A sell-out 65,000 people are expected at Joshua's heavyweight unification bout with New Zealander Joseph Parker.
The main fight starts at 22:30 BST but the final train to Bristol is 22:47, 23:08 to Bridgend and Swansea and the last one to London is 21:25.
A council-run city centre taxi marshal service will end at midnight.
But the service, which manages queues for taxis at Greyfriars Road and lower St Mary Street, will continue to be run by local businesses after midnight.
Cardiff council has warned demand for taxis is expected to be "very high after the event" and said people are advised to book their taxi home in advance.
Roads in Cardiff city centre will shut at 16:00 ahead of the Principality Stadium gates opening at 17:00.
Cardiff road closures will be in operation from 16:00 BST
Train companies are advising fans to arrive early as they say services will be "busy all day".
Signal upgrade work at Bristol Temple Meads means buses will replace trains between Bristol and the south and south-west of England all weekend.
Rail passengers are also advised to check local services as the last trains to Newport, Merthyr Tydfil, Ystrad Mynach and Barry Island could also leave before the fight has finished.
The stadium has warned fans to expect "enhanced security checks" entering the arena as the UK terror threat remains severe.
A Principality Stadium spokesman said it "works closely" with the Wales Extremism and Counter Terrorism Unit but police had stressed there was no specific threat to Cardiff.
Cardiff Bus, which is diverting services away from city centre stops, will provide late night services, with the last buses leaving the city centre at 03:30.
Transport authorities have also said the M4 corridor into and out of Cardiff is expected to be "very busy".