In the track day setup, use the "Restrictor" option on traffic cars to force them to drive at normal speed limits instead of racing speeds.
Advanced maps like Shutoko Expressway utilize dedicated traffic tools built into modern versions of CSP. Assetto Corsa City Map With Traffic Mod
Turn on the option. This mechanic continuously spawns traffic cars just ahead of you and deletes them once they are far behind you, saving system memory. How to Launch a Traffic Session In the track day setup, use the "Restrictor"