There's a way to restart individual races:
-save before starting a race (suspend championship)
-press PS home button to quit the game
-start the game and play the race
-if something happens and you wish to restart the race press the PS home button to quit the game, when you load the game you'll be back at the beginning of the race you quit.
I'd rather have the option to press start and restart the race (something that's available in every other racing game out there), but the steps above are an OK workaround if something happens (like some stupid AI car taking you out for instance).
As for the comments against restarts, and being a driving simulator: in career mode there's no qualifying, races are in catch-up format, grids are unbalanced, there's no option to enable mechanical damage, no option to enable corner cutting penalties or collision penalties, and one can use unrealistic aids such as driving line and SRF. So, don't give me that bs about the game being "the real driving simulator."