When doing race events in career mode, there is a way to change the amount of traffic, catch-up on/off, and number of laps.
For example, there is a race in "Race events" in the blacklist menu. It is a sprint type race, and the track is "Seagate & Camden". Go back to the main menu, and select quick race. Select custom race, and do a sprint on "Seagate & Camden". Set the options you want (i.e. No traffic, etc). Do the race. Go back into career mode and do that same race in the blacklist menu. Those options you selected in quick race mode will apply here. You can have no traffic, and turn off catch-up. It also means if you have a 4-lap circuit race in career mode, you can do this cheat and only have to do 1 lap.