The best solution is to ban all personal vehicles from the city centre, and convert the city centre into a large pedestrian zone.
Service vehicles and delivery vehicles may still be able to go into the pedestrian zone, but with permission only.
The city centre would then become accessible by public transport, such as with a tram or an underground metro.
Outer areas of the city would still feature regular roads and further out of the city, park & ride facilities will allow people who still commute by car to get to a point outside of the city and complete their journey by public transport. Realistically, all traffic not needing to go to the city should not be in the city, and should go onto bypass roads and highways.
By the way, if someone wants to know what I mean by "city centre", I mean the Central Business District, (CBD). These will be the key shopping and entertainment areas in the city as well as where major offices and corporate buildings will be located.