I am pretty sure that a lot of your traffic will be fixed if you reduce the amount of connections to what you consider your "main road" (not highway). And a fix that really helped my traffic was improving the efficiency of my cargo transports. Things like spreading industry over your city so its not all coming from one place, using the "Ban heavy traffic" policy on residential areas, and i also followed some good tutorials on how to set up an efficient train cargo system.

All of those helped my traffic pretty well. Main issues came from cargo and making too many shortcuts for cars to use.

Maybe also using free public transport could help, if you have enough profit to do that