I'm sure it varies some by venue, but in my experience pit pass at IndyCar will get you as close as you want, as long as you don't get in the way, and don't try

I'm sure it varies some by venue, but in my experience pit pass at IndyCar will get you as close as you want, as long as you don't get in the way, and don't try to go on the car-side of the jersey barrier.