Most of it. It's much cheaper to do a lot of the stuff on a computer than to hire the drivers, buy the cars, set up remote location shoots, bring dozens and dozens of people and tons of equipment to the site, cater the shoot, buy the insurance, get the permits to block traffic, worry about the weather, etc.
And the F&F movies are basically aimed at teenage gamers, they're not "serious" movies...so realism isn't even an issue–it's all about movement, action and flashing lights/explosions/crashes. Gotta keep the kid's attention span focused... for at least a few seconds!