If adding lanes doesn't help you didn't add enough. People live in a city to do things and you need to enable that by preventing congestion.
i don't know how to afford the 50 more lanes that most cities need though. I suggest better transit.
Removing parts of the city to add more lanes will also help decreasing demand - it's a win-win!
Removing parts of the city to add more lanes will also help decreasing demand - it's a win-win!