If you feel dirty using a finished save, but you hate the grind, try these mods instead:
These provide a middle ground between grinding and cheating.
Open File Explorer and paste the appropriate path:
Once the story is 100% complete, the "Director Mode" becomes fully customizable. You can set traffic density, time of day, weather (fog on the bridge is stunning), and even trigger police aggression levels. Without a complete save, these sliders are locked.