'Arrive early' advice for Wales v Scotland Six Nations game
Rugby fans were warned to arrive at the Principality Stadium early on Saturday or face missing kick-off.
Wales began their Six Nations campaign against Scotland in front of a 74,500 sell-out crowd, with 100,000 people expected in the city.
A road closure started at 10:45 GMT before the 14:15 kick-off.
Wales made a dream start to the tournament as they crushed Scotland 34-7.
Great Western Railway added 11 extra mainline trains to and from Cardiff in both directions before and after the game.
Increased security checks were in place at the stadium because the UK terror threat remained at severe.
The extra security was expected to slow people down entering the ground, but no major issues were reported.
Cardiff road closures have been in operation since 10:45 GMT
Welsh rugby bosses and the police wanted at least 30,000 supporters in the ground before 12:45 because they did not want a repeat of the queues that marred their autumn game against Australia in November, when many fans missed kick-off.
"It's not something that our rugby supporters will be used to if they didn't come to a game in the autumn," said Insp Phillip Griffiths of South Wales Police.
"We know we can get everyone in safely and securely and ensure they don't miss a minute of the game, but we need supporters to help us."
The Principality Stadium "works closely" with the Wales Extremism and Counter Terrorism Unit but police had stressed there was no specific threat to Cardiff.
Supporters travelling to the game were warned that the A465 Heads of the Valleys road between Gilwern and Brynmawr was shut.
The M4 motorway is also shut westbound at the Brynglas Tunnels in Newport from 19:00 on Saturday until 10:00 on Sunday for upgrade works.
GWR added extra trains between Cardiff and Swansea, Port Talbot, Bristol and London.
Cardiff Buses were diverted out of the central city bus stops and terminated at either Churchill Way, Greyfriars Road or Tudor Street.