Been doing and watching a bunch of NR4 and NR2003 superspeedway racing, and I've had a realization about what sets apart NR4's AI racing on superspeedways.
C
ars in NR4 in a single file train tend to go significantly faster than when cars are side-by-side or three-wide in a pack (especially through the corners). From memory, it's a difference of 5 mph or more (e.g. 190 vs. 185 mph).
This has a single
huge benefit. It means that in NR4, by getting into single file,
one group of cars can actually catch up to another! Whereas in NR2003, if a pack breaks away at the front, it runs away... a group behind it will never catch up under green flag conditions.
It makes longer races with AI much more engaging in NR4 if you start or slip towards the rear of the field. You might actually catch up. Even towards the back of the field, the cars never quite permanently lose touch. And, like in real life, there's actually a benefit to running behind a fast car and bumping them along the straight to try to catch up to a group ahead. It makes it not feel like a snooze-fest when cars are in single-file... you know you may be catching cars ahead.
I wonder if there's a parameter or two in the NR2003 EXE (perhaps related to side draft) that you could adjust to slow cars down when side-by-side to create the same effect as NR4. Given what I've realized about NR4, it might make a huge difference.
A few other things I've noticed about NR4 – some of which have already been noted in other posts above, but I'll put here for completeness' sake:
1. Even at Daytona, you can't flat-foot the car through the corner (especially on entry) which makes the driving more engaging, and is true to life
even for the early-mid 2000s superspeedway packages;
2. The speed gains from the draft seem stronger and to extend further back than in NR2003, which makes the racing more engaging and may (or may not) also affect the extra speed in single-file trains;
3. There is more grip on the bottom than the middle, and even less on top, which is an issue that is lesser but still present into NR2003 (Brian Ring tracks aside) but artificially helps create variety by inducing a line of faster cars on the bottom (which can then break away in single-file and catch up to groups ahead);
4. I'm less confident about this, but it seems speed in the draft is sometimes affected by some kind of 'adaptive speed control' where your speed is partially dictated by that of the car in front... I've had my speed drop significantly (e.g. 5 mph) with my foot flat to the floor when approaching a pack of cars up ahead that are running slower.
Finally, I'll just share this video from GPLaps, in case anyone hasn't seen it. A fantastic showcase of what NR4 can do.