South Wales Police are urging fans to enjoy the day ahead of the Cardiff City v Swansea City match at the Cardiff City Stadium on Saturday, April 3.
Officers have reassured fans, residents and businesses that plans are in place to ensure the day is policed efficiently and effectively.
Divisional Commander for Cardiff, Chief Superintendent Josh Jones said: "We recognise this is a very important fixture for both clubs as once again they find themselves seeking promotion to the Premier League.
"It's a local derby and we know how passionate fans are about this particular game.
"There will be a substantial police presence to ensure the safety of spectators and the wider community.
"We will be utilising our vast experience gained over the years in policing many major sporting events, including derby games, to ensure the day is run smoothly, and, most importantly, enjoyed by the fans.
"My message to anyone thinking about causing trouble is - don't forget about the potential that your team may be promoted to the Premier League or play each other in the play-offs.
"If you come to this event and misbehave, we will have no hesitation in banning you, which means you may miss a very important fixture in May, or miss the likes of Liverpool or Manchester United visiting South Wales next season."
The match kicks off at 5.20pm. As on a normal match day, there may be some congestion in the area of the Cardiff City Stadium before the kick off, which may build from around 4pm. Likewise there will be congestion at the conclusion of the game from about 7pm onwards.
A club statement said:
The game on Saturday is the first Welsh derby at Cardiff City Stadium.
It is also considered by many to be one of the most important modern-day Welsh derbies as both teams strive for play-off positions.
Everything points to a thrilling encounter with an atmosphere to match, and we are sure that all supporters will enjoy the occasion.
The design of the new stadium, control measures for visiting supporters and confidence in the ability of stewards and police has enabled the club to facilitate a 5.20pm kick-off and the game will be shown live on Sky TV.
Cardiff City Football Club works closely with South Wales Police to enforce the ground regulations and it should be noted that at this fixture particular attention will be made to any alcohol-related offences.
We expect all supporters attending this fixture to do so in the correct manner and show true support for their team.
Enjoy the match.
